sim: bfin: push down mmr address/size checks

The bfin port is using the WITH_DEVICES framework for two reasons:
- get access to the cpu making the request (if available)
- check the alignment & size for core & system MMRs

We addressed the first part with commit dea10706e9159ba6e94eab4c25010f3,
and we handle the second part with this commit.  Arguably this is more
correct too because trying to do bad reads/writes directly (when devices
support is disabled) often results in bad memory accesses.

As part of this clean up, we also adjust all of the existing logic that
would reject invalid accesses: the code was relying on the checks never
returning, but that's not the case when things like gdb (via the user's
commands) are making the requests.  Thus we'd still end up with bad mem
accesses, or sometimes gdb being hung due to while(1) loops.

Now we can connect (most of) these models into any address and have them
work correctly.

33 files changed, 549 insertions, 229 deletions

diff --git a/sim/bfin/ChangeLog b/sim/bfin/ChangeLog
index fb00c8b..2bdfc6e 100644
--- a/sim/bfin/ChangeLog
+++ b/sim/bfin/ChangeLog
@@ -1,5 +1,127 @@
 2015-12-26  Mike Frysinger  <vapier@gentoo.org>
 
+	* devices.c (bfin_mmr_invalid): Delete cpu arg and add missing arg.
+	Add cpu, rw, and reason local vars.  Rewrite error messages.  Add
+	more todo comments.
+	(dv_bfin_mmr_invalid): Update bfin_mmr_invalid call.
+	(dv_bfin_mmr_require): Likewise.  Change return to bool.  Check
+	alignment of the addr variable.
+	(bfin_mmr_check, dv_bfin_mmr_check, device_io_read_buffer,
+	device_io_write_buffer): Delete.
+	(dv_bfin_mmr_require_16_32): Define.
+	* devices.h (dv_bfin_mmr_require): Change return to bool.
+	(dv_bfin_mmr_check): Delete.
+	(dv_bfin_mmr_require_16_32): Define.
+	Add a few comments.
+	* dv-bfin_cec.c (bfin_cec_io_write_buffer): Call
+	dv_bfin_mmr_require_32.
+	(bfin_cec_io_read_buffer): Likewise.
+	* dv-bfin_ctimer.c (bfin_ctimer_io_write_buffer): Likewise.
+	(bfin_ctimer_io_read_buffer): Likewise.
+	* dv-bfin_dma.c (bfin_dma_io_write_buffer): Call
+	dv_bfin_mmr_require_16_32.  Return 0 in the default case.
+	(bfin_dma_io_read_buffer): Call dv_bfin_mmr_require_16_32.
+	* dv-bfin_ebiu_amc.c (bf50x_ebiu_amc_io_write_buffer): Return 0
+	when dv_bfin_mmr_require_16 fails and in the default case.
+	(bf53x_ebiu_amc_io_write_buffer): Likewise.
+	(bf54x_ebiu_amc_io_write_buffer): Likewise.
+	(bfin_ebiu_amc_io_write_buffer): Call dv_bfin_mmr_require_16_32.
+	(bf50x_ebiu_amc_io_read_buffer): Return 0 when
+	dv_bfin_mmr_require_16 fails and in the default case.
+	(bf53x_ebiu_amc_io_read_buffer): Likewise.
+	(bf54x_ebiu_amc_io_read_buffer): Likewise.
+	(bfin_ebiu_amc_io_read_buffer): Call dv_bfin_mmr_require_16_32.
+	* dv-bfin_ebiu_ddrc.c (bfin_ebiu_ddrc_io_write_buffer): Call
+	dv_bfin_mmr_require_16_32.  Return 0 when dv_bfin_mmr_require_16 or
+	dv_bfin_mmr_require_32 fails.
+	(bfin_ebiu_ddrc_io_read_buffer): Likewise.
+	* dv-bfin_ebiu_sdc.c (bfin_ebiu_sdc_io_write_buffer): Likewise.
+	(bfin_ebiu_sdc_io_read_buffer): Likewise.
+	* dv-bfin_emac.c (bfin_emac_io_write_buffer): Return 0 when
+	dv_bfin_mmr_require_32 fails and in the default case.
+	(bfin_emac_io_read_buffer): Likewise.
+	* dv-bfin_eppi.c (bfin_eppi_io_write_buffer): Call
+	dv_bfin_mmr_require_16_32 and return 0 when dv_bfin_mmr_require_16
+	or dv_bfin_mmr_require_32 fails and in the default case.
+	(bfin_eppi_io_read_buffer): Likewise.
+	* dv-bfin_evt.c (bfin_evt_io_write_buffer): Call
+	dv_bfin_mmr_require_32.
+	(bfin_evt_io_read_buffer): Likewise.
+	* dv-bfin_gpio.c (bfin_gpio_io_write_buffer): Move call to
+	dv_bfin_mmr_require_16 to earlier in the func.  Return 0 when it
+	fails and in the default case.
+	(bfin_gpio_io_read_buffer): Likewise.
+	* dv-bfin_gpio2.c (bfin_gpio_io_write_buffer): Move call to
+	dv_bfin_mmr_require_16 and dv_bfin_mmr_require_32 to earlier in the
+	func.  Return 0 when it fails and in the default case.
+	(bfin_gpio_io_read_buffer): Likewise.
+	* dv-bfin_gptimer.c (bfin_gptimer_io_write_buffer): Call
+	dv_bfin_mmr_require_16_32.  Return 0 when dv_bfin_mmr_require_16 or
+	dv_bfin_mmr_require_32 fails and in the default case.
+	(bfin_gptimer_io_read_buffer): Likewise.
+	* dv-bfin_jtag.c (bfin_jtag_io_write_buffer): Call
+	dv_bfin_mmr_require_32.  Return 0 in the default case.
+	(bfin_jtag_io_read_buffer): Likewise.  Delete while(1) loop.
+	* dv-bfin_mmu.c (bfin_mmu_io_write_buffer): Call
+	dv_bfin_mmr_require_32.  Return 0 in the default case.
+	(bfin_mmu_io_read_buffer): Likewise.  Delete while(1) loop.
+	* dv-bfin_nfc.c (bfin_nfc_io_write_buffer): Move call to
+	dv_bfin_mmr_require_16 to earlier in the func.  Return 0 when it
+	fails and in the default case.
+	(bfin_nfc_io_read_buffer): Likewise.
+	* dv-bfin_otp.c (bfin_otp_io_write_buffer): Call
+	dv_bfin_mmr_require_16_32.  Return 0 when dv_bfin_mmr_require_16
+	or dv_bfin_mmr_require_32 fails and in the default case.
+	(bfin_otp_io_read_buffer): Likewise.
+	* dv-bfin_pfmon.c (bfin_pfmon_io_write_buffer): Call
+	dv_bfin_mmr_require_32.  Return 0 in the default case.
+	(bfin_pfmon_io_read_buffer): Likewise.  Delete while(1) loop.
+	* dv-bfin_pint.c (bfin_pint_io_write_buffer): Move call to
+	dv_bfin_mmr_require_32 to earlier in the func.  Return 0 when it
+	fails and in the default case.
+	(bfin_pint_io_read_buffer): Likewise.
+	* dv-bfin_pll.c (bfin_pll_io_write_buffer): Call
+	dv_bfin_mmr_require_16_32.  Return 0 when dv_bfin_mmr_require_16
+	fails.
+	(bfin_pll_io_read_buffer): Likewise.
+	* dv-bfin_ppi.c (bfin_ppi_io_write_buffer): Move call to
+	dv_bfin_mmr_require_16 to earlier in the func.  Return 0 when it
+	fails and in the default case.
+	9bfin_ppi_io_read_buffer): Likewise.
+	* dv-bfin_rtc.c (bfin_rtc_io_write_buffer): Call
+	dv_bfin_mmr_require_16_32.
+	(bfin_rtc_io_read_buffer): Likewise.
+	* dv-bfin_sic.c (bfin_sic_52x_io_write_buffer): Likewise.
+	(bfin_sic_52x_io_read_buffer, bfin_sic_537_io_write_buffer,
+	bfin_sic_537_io_read_buffer, bfin_sic_54x_io_write_buffer,
+	bfin_sic_54x_io_read_buffer, bfin_sic_561_io_write_buffer,
+	bfin_sic_561_io_read_buffer): Likewise.
+	* dv-bfin_spi.c (bfin_spi_io_write_buffer): Move call to
+	dv_bfin_mmr_require_16 to earlier in the func.  Return 0 when it
+	fails and in the default case.
+	(bfin_spi_io_read_buffer): Likewise.
+	* dv-bfin_trace.c (bfin_trace_io_write_buffer): Call
+	dv_bfin_mmr_require_32.  Return 0 in the default case.
+	(bfin_trace_io_read_buffer): Likewise.  Delete while(1) loop.
+	* dv-bfin_twi.c (bfin_twi_io_write_buffer): Move call to
+	dv_bfin_mmr_require_16 to earlier in the func.  Return 0 when it
+	fails and in the default case.
+	(bfin_twi_io_read_buffer): Likewise.
+	* dv-bfin_uart.c (bfin_uart_io_write_buffer): Likewise.
+	(bfin_uart_io_read_buffer): Likewise.
+	* dv-bfin_uart2.c (bfin_uart_io_write_buffer): Likewise.
+	(bfin_uart_io_read_buffer): Likewise.
+	* dv-bfin_wdog.c (bfin_wdog_io_write_buffer): Call
+	dv_bfin_mmr_require_16_32.
+	(bfin_wdog_io_read_buffer): Likewise.  Return 0 when
+	dv_bfin_mmr_require_16 fails.
+	* dv-bfin_wp.c (bfin_wp_io_write_buffer): Call
+	dv_bfin_mmr_require_32.  Return 0 in the default case.
+	(bfin_wp_io_read_buffer): Likewise.  Delete while(1) loop.
+	* tconfig.h: Delete file.
+
+2015-12-26  Mike Frysinger  <vapier@gentoo.org>
+
 	* bfin-sim.c (decode_LDST_0): Add 4th element to posts array.
 
 2015-12-26  Mike Frysinger  <vapier@gentoo.org>
diff --git a/sim/bfin/devices.c b/sim/bfin/devices.c
index 7dab5f1..aec27d6 100644
--- a/sim/bfin/devices.c
+++ b/sim/bfin/devices.c
@@ -28,25 +28,32 @@
 #include "dv-bfin_mmu.h"
 
 static void
-bfin_mmr_invalid (struct hw *me, SIM_CPU *cpu, address_word addr,
-		  unsigned nr_bytes, bool write)
+bfin_mmr_invalid (struct hw *me, address_word addr,
+		  unsigned nr_bytes, bool write, bool missing)
 {
-  if (!cpu)
-    cpu = hw_system_cpu (me);
+  SIM_CPU *cpu = hw_system_cpu (me);
+  const char *rw = write ? "write" : "read";
+  const char *reason =
+    missing ? "no such register" :
+              (addr & 3) ? "must be 32-bit aligned" : "invalid length";
 
   /* Only throw a fit if the cpu is doing the access.  DMA/GDB simply
      go unnoticed.  Not exactly hardware behavior, but close enough.  */
   if (!cpu)
     {
-      sim_io_eprintf (hw_system (me), "%s: invalid MMR access @ %#x\n",
-		      hw_path (me), addr);
+      sim_io_eprintf (hw_system (me),
+		      "%s: invalid MMR %s at %#x length %u: %s\n",
+		      hw_path (me), rw, addr, nr_bytes, reason);
       return;
     }
 
-  HW_TRACE ((me, "invalid MMR %s to 0x%08lx length %u",
-	     write ? "write" : "read", (unsigned long) addr, nr_bytes));
+  HW_TRACE ((me, "invalid MMR %s at %#x length %u: %s",
+	     rw, addr, nr_bytes, reason));
 
-  /* XXX: is this what hardware does ?  */
+  /* XXX: is this what hardware does ?  What about priority of unaligned vs
+     wrong length vs missing register ?  What about system-vs-core ?  */
+  /* XXX: We should move this addr check to a model property so we get the
+     same behavior regardless of where we map the model.  */
   if (addr >= BFIN_CORE_MMR_BASE)
     /* XXX: This should be setting up CPLB fault addrs ?  */
     mmu_process_fault (cpu, addr, write, false, false, true);
@@ -60,93 +67,30 @@ void
 dv_bfin_mmr_invalid (struct hw *me, address_word addr, unsigned nr_bytes,
 		     bool write)
 {
-  bfin_mmr_invalid (me, NULL, addr, nr_bytes, write);
+  bfin_mmr_invalid (me, addr, nr_bytes, write, true);
 }
 
-void
+bool
 dv_bfin_mmr_require (struct hw *me, address_word addr, unsigned nr_bytes,
 		     unsigned size, bool write)
 {
-  if (nr_bytes != size)
-    dv_bfin_mmr_invalid (me, addr, nr_bytes, write);
-}
-
-static bool
-bfin_mmr_check (struct hw *me, SIM_CPU *cpu, address_word addr,
-		unsigned nr_bytes, bool write)
-{
-  if (addr >= BFIN_CORE_MMR_BASE)
-    {
-      /* All Core MMRs are aligned 32bits.  */
-      if ((addr & 3) == 0 && nr_bytes == 4)
-	return true;
-    }
-  else if (addr >= BFIN_SYSTEM_MMR_BASE)
-    {
-      /* All System MMRs are 32bit aligned, but can be 16bits or 32bits.  */
-      if ((addr & 0x3) == 0 && (nr_bytes == 2 || nr_bytes == 4))
-	return true;
-    }
-  else
+  if ((addr & 0x3) == 0 && nr_bytes == size)
     return true;
 
-  /* Still here ?  Must be crap.  */
-  bfin_mmr_invalid (me, cpu, addr, nr_bytes, write);
-
+  bfin_mmr_invalid (me, addr, nr_bytes, write, false);
   return false;
 }
 
+/* For 32-bit memory mapped registers that allow 16-bit or 32-bit access.  */
 bool
-dv_bfin_mmr_check (struct hw *me, address_word addr, unsigned nr_bytes,
-		   bool write)
-{
-  return bfin_mmr_check (me, NULL, addr, nr_bytes, write);
-}
-
-int
-device_io_read_buffer (device *me, void *source, int space,
-		       address_word addr, unsigned nr_bytes,
-		       SIM_DESC sd, SIM_CPU *cpu, sim_cia cia)
+dv_bfin_mmr_require_16_32 (struct hw *me, address_word addr, unsigned nr_bytes,
+			   bool write)
 {
-  struct hw *dv_me = (struct hw *) me;
-
-  if (STATE_ENVIRONMENT (sd) != OPERATING_ENVIRONMENT)
-    return nr_bytes;
-
-  if (bfin_mmr_check (dv_me, cpu, addr, nr_bytes, false))
-    if (cpu)
-      {
-	sim_cpu_hw_io_read_buffer (cpu, cia, dv_me, source, space,
-				   addr, nr_bytes);
-	return nr_bytes;
-      }
-    else
-      return sim_hw_io_read_buffer (sd, dv_me, source, space, addr, nr_bytes);
-  else
-    return 0;
-}
+  if ((addr & 0x3) == 0 && (nr_bytes == 2 || nr_bytes == 4))
+    return true;
 
-int
-device_io_write_buffer (device *me, const void *source, int space,
-			address_word addr, unsigned nr_bytes,
-                        SIM_DESC sd, SIM_CPU *cpu, sim_cia cia)
-{
-  struct hw *dv_me = (struct hw *) me;
-
-  if (STATE_ENVIRONMENT (sd) != OPERATING_ENVIRONMENT)
-    return nr_bytes;
-
-  if (bfin_mmr_check (dv_me, cpu, addr, nr_bytes, true))
-    if (cpu)
-      {
-	sim_cpu_hw_io_write_buffer (cpu, cia, dv_me, source, space,
-				    addr, nr_bytes);
-	return nr_bytes;
-      }
-    else
-      return sim_hw_io_write_buffer (sd, dv_me, source, space, addr, nr_bytes);
-  else
-    return 0;
+  bfin_mmr_invalid (me, addr, nr_bytes, write, false);
+  return false;
 }
 
 unsigned int dv_get_bus_num (struct hw *me)
diff --git a/sim/bfin/devices.h b/sim/bfin/devices.h
index a077d55..9bbcfe2 100644
--- a/sim/bfin/devices.h
+++ b/sim/bfin/devices.h
@@ -133,10 +133,12 @@ dv_get_state (SIM_CPU *cpu, const char *device_name)
   })
 
 void dv_bfin_mmr_invalid (struct hw *, address_word, unsigned nr_bytes, bool write);
-void dv_bfin_mmr_require (struct hw *, address_word, unsigned nr_bytes, unsigned size, bool write);
-bool dv_bfin_mmr_check (struct hw *, address_word, unsigned nr_bytes, bool write);
-
+bool dv_bfin_mmr_require (struct hw *, address_word, unsigned nr_bytes, unsigned size, bool write);
+/* For 32-bit memory mapped registers that allow 16-bit or 32-bit access.  */
+bool dv_bfin_mmr_require_16_32 (struct hw *, address_word, unsigned nr_bytes, bool write);
+/* For 32-bit memory mapped registers that only allow 16-bit access.  */
 #define dv_bfin_mmr_require_16(hw, addr, nr_bytes, write) dv_bfin_mmr_require (hw, addr, nr_bytes, 2, write)
+/* For 32-bit memory mapped registers that only allow 32-bit access.  */
 #define dv_bfin_mmr_require_32(hw, addr, nr_bytes, write) dv_bfin_mmr_require (hw, addr, nr_bytes, 4, write)
 
 #define HW_TRACE_WRITE() \
diff --git a/sim/bfin/dv-bfin_cec.c b/sim/bfin/dv-bfin_cec.c
index 186edcb..8ce0d2c 100644
--- a/sim/bfin/dv-bfin_cec.c
+++ b/sim/bfin/dv-bfin_cec.c
@@ -82,6 +82,10 @@ bfin_cec_io_write_buffer (struct hw *me, const void *source,
   bu32 mmr_off;
   bu32 value;
 
+  /* Invalid access mode is higher priority than missing register.  */
+  if (!dv_bfin_mmr_require_32 (me, addr, nr_bytes, true))
+    return 0;
+
   value = dv_load_4 (source);
   mmr_off = addr - cec->base;
 
@@ -118,6 +122,10 @@ bfin_cec_io_read_buffer (struct hw *me, void *dest,
   bu32 mmr_off;
   bu32 *valuep;
 
+  /* Invalid access mode is higher priority than missing register.  */
+  if (!dv_bfin_mmr_require_32 (me, addr, nr_bytes, false))
+    return 0;
+
   mmr_off = addr - cec->base;
   valuep = (void *)((unsigned long)cec + mmr_base() + mmr_off);
 
diff --git a/sim/bfin/dv-bfin_ctimer.c b/sim/bfin/dv-bfin_ctimer.c
index 6aa5c31..f361cb2 100644
--- a/sim/bfin/dv-bfin_ctimer.c
+++ b/sim/bfin/dv-bfin_ctimer.c
@@ -127,6 +127,10 @@ bfin_ctimer_io_write_buffer (struct hw *me, const void *source,
   bu32 value;
   bu32 *valuep;
 
+  /* Invalid access mode is higher priority than missing register.  */
+  if (!dv_bfin_mmr_require_32 (me, addr, nr_bytes, true))
+    return 0;
+
   value = dv_load_4 (source);
   mmr_off = addr - ctimer->base;
   valuep = (void *)((unsigned long)ctimer + mmr_base() + mmr_off);
@@ -192,6 +196,10 @@ bfin_ctimer_io_read_buffer (struct hw *me, void *dest,
   bu32 mmr_off;
   bu32 *valuep;
 
+  /* Invalid access mode is higher priority than missing register.  */
+  if (!dv_bfin_mmr_require_32 (me, addr, nr_bytes, false))
+    return 0;
+
   mmr_off = addr - ctimer->base;
   valuep = (void *)((unsigned long)ctimer + mmr_base() + mmr_off);
 
diff --git a/sim/bfin/dv-bfin_dma.c b/sim/bfin/dv-bfin_dma.c
index 33a80f3..c329ab7 100644
--- a/sim/bfin/dv-bfin_dma.c
+++ b/sim/bfin/dv-bfin_dma.c
@@ -318,6 +318,10 @@ bfin_dma_io_write_buffer (struct hw *me, const void *source, int space,
   bu32 *value32p;
   void *valuep;
 
+  /* Invalid access mode is higher priority than missing register.  */
+  if (!dv_bfin_mmr_require_16_32 (me, addr, nr_bytes, true))
+    return 0;
+
   if (nr_bytes == 4)
     value = dv_load_4 (source);
   else
@@ -401,7 +405,7 @@ bfin_dma_io_write_buffer (struct hw *me, const void *source, int space,
     default:
       /* XXX: The HW lets the pad regions be read/written ...  */
       dv_bfin_mmr_invalid (me, addr, nr_bytes, true);
-      break;
+      return 0;
     }
 
   return nr_bytes;
@@ -417,6 +421,10 @@ bfin_dma_io_read_buffer (struct hw *me, void *dest, int space,
   bu32 *value32p;
   void *valuep;
 
+  /* Invalid access mode is higher priority than missing register.  */
+  if (!dv_bfin_mmr_require_16_32 (me, addr, nr_bytes, false))
+    return 0;
+
   mmr_off = addr % dma->base;
   valuep = (void *)((unsigned long)dma + mmr_base() + mmr_off);
   value16p = valuep;
diff --git a/sim/bfin/dv-bfin_ebiu_amc.c b/sim/bfin/dv-bfin_ebiu_amc.c
index 3bdae61..623d696 100644
--- a/sim/bfin/dv-bfin_ebiu_amc.c
+++ b/sim/bfin/dv-bfin_ebiu_amc.c
@@ -121,7 +121,8 @@ bf50x_ebiu_amc_io_write_buffer (struct hw *me, const void *source, int space,
   switch (mmr_off)
     {
     case mmr_offset(amgctl):
-      dv_bfin_mmr_require_16 (me, addr, nr_bytes, true);
+      if (!dv_bfin_mmr_require_16 (me, addr, nr_bytes, true))
+	return 0;
       bfin_ebiu_amc_write_amgctl (me, amc, value);
       break;
     case mmr_offset(bf50x.ambctl0):
@@ -132,15 +133,17 @@ bf50x_ebiu_amc_io_write_buffer (struct hw *me, const void *source, int space,
       break;
     case mmr_offset(bf50x.mode):
       /* XXX: implement this.  */
-      dv_bfin_mmr_require_16 (me, addr, nr_bytes, true);
+      if (!dv_bfin_mmr_require_16 (me, addr, nr_bytes, true))
+	return 0;
       break;
     case mmr_offset(bf50x.fctl):
       /* XXX: implement this.  */
-      dv_bfin_mmr_require_16 (me, addr, nr_bytes, true);
+      if (!dv_bfin_mmr_require_16 (me, addr, nr_bytes, true))
+	return 0;
       break;
     default:
       dv_bfin_mmr_invalid (me, addr, nr_bytes, true);
-      break;
+      return 0;
     }
 
   return nr_bytes;
@@ -155,7 +158,8 @@ bf53x_ebiu_amc_io_write_buffer (struct hw *me, const void *source, int space,
   switch (mmr_off)
     {
     case mmr_offset(amgctl):
-      dv_bfin_mmr_require_16 (me, addr, nr_bytes, true);
+      if (!dv_bfin_mmr_require_16 (me, addr, nr_bytes, true))
+	return 0;
       bfin_ebiu_amc_write_amgctl (me, amc, value);
       break;
     case mmr_offset(bf53x.ambctl0):
@@ -166,7 +170,7 @@ bf53x_ebiu_amc_io_write_buffer (struct hw *me, const void *source, int space,
       break;
     default:
       dv_bfin_mmr_invalid (me, addr, nr_bytes, true);
-      break;
+      return 0;
     }
 
   return nr_bytes;
@@ -181,7 +185,8 @@ bf54x_ebiu_amc_io_write_buffer (struct hw *me, const void *source, int space,
   switch (mmr_off)
     {
     case mmr_offset(amgctl):
-      dv_bfin_mmr_require_16 (me, addr, nr_bytes, true);
+      if (!dv_bfin_mmr_require_16 (me, addr, nr_bytes, true))
+	return 0;
       bfin_ebiu_amc_write_amgctl (me, amc, value);
       break;
     case mmr_offset(bf54x.ambctl0):
@@ -204,7 +209,7 @@ bf54x_ebiu_amc_io_write_buffer (struct hw *me, const void *source, int space,
       break;
     default:
       dv_bfin_mmr_invalid (me, addr, nr_bytes, true);
-      break;
+      return 0;
     }
 
   return nr_bytes;
@@ -218,6 +223,10 @@ bfin_ebiu_amc_io_write_buffer (struct hw *me, const void *source, int space,
   bu32 mmr_off;
   bu32 value;
 
+  /* Invalid access mode is higher priority than missing register.  */
+  if (!dv_bfin_mmr_require_16_32 (me, addr, nr_bytes, true))
+    return 0;
+
   value = dv_load_4 (source);
   mmr_off = addr - amc->base;
 
@@ -237,7 +246,8 @@ bf50x_ebiu_amc_io_read_buffer (struct hw *me, void *dest, int space,
     {
     case mmr_offset(amgctl):
     case mmr_offset(bf50x.fctl):
-      dv_bfin_mmr_require_16 (me, addr, nr_bytes, false);
+      if (!dv_bfin_mmr_require_16 (me, addr, nr_bytes, false))
+	return 0;
       dv_store_2 (dest, *value16);
       break;
     case mmr_offset(bf50x.ambctl0):
@@ -247,7 +257,7 @@ bf50x_ebiu_amc_io_read_buffer (struct hw *me, void *dest, int space,
       break;
     default:
       dv_bfin_mmr_invalid (me, addr, nr_bytes, false);
-      break;
+      return 0;
     }
 
   return nr_bytes;
@@ -262,7 +272,8 @@ bf53x_ebiu_amc_io_read_buffer (struct hw *me, void *dest, int space,
   switch (mmr_off)
     {
     case mmr_offset(amgctl):
-      dv_bfin_mmr_require_16 (me, addr, nr_bytes, false);
+      if (!dv_bfin_mmr_require_16 (me, addr, nr_bytes, false))
+	return 0;
       dv_store_2 (dest, *value16);
       break;
     case mmr_offset(bf53x.ambctl0):
@@ -271,7 +282,7 @@ bf53x_ebiu_amc_io_read_buffer (struct hw *me, void *dest, int space,
       break;
     default:
       dv_bfin_mmr_invalid (me, addr, nr_bytes, false);
-      break;
+      return 0;
     }
 
   return nr_bytes;
@@ -286,7 +297,8 @@ bf54x_ebiu_amc_io_read_buffer (struct hw *me, void *dest, int space,
   switch (mmr_off)
     {
     case mmr_offset(amgctl):
-      dv_bfin_mmr_require_16 (me, addr, nr_bytes, false);
+      if (!dv_bfin_mmr_require_16 (me, addr, nr_bytes, false))
+	return 0;
       dv_store_2 (dest, *value16);
       break;
     case mmr_offset(bf54x.ambctl0):
@@ -299,7 +311,7 @@ bf54x_ebiu_amc_io_read_buffer (struct hw *me, void *dest, int space,
       break;
     default:
       dv_bfin_mmr_invalid (me, addr, nr_bytes, false);
-      break;
+      return 0;
     }
 
   return nr_bytes;
@@ -313,6 +325,10 @@ bfin_ebiu_amc_io_read_buffer (struct hw *me, void *dest, int space,
   bu32 mmr_off;
   void *valuep;
 
+  /* Invalid access mode is higher priority than missing register.  */
+  if (!dv_bfin_mmr_require_16_32 (me, addr, nr_bytes, false))
+    return 0;
+
   mmr_off = addr - amc->base;
   valuep = (void *)((unsigned long)amc + mmr_base() + mmr_off);
 
diff --git a/sim/bfin/dv-bfin_ebiu_ddrc.c b/sim/bfin/dv-bfin_ebiu_ddrc.c
index 51e1ed2..b0b820f 100644
--- a/sim/bfin/dv-bfin_ebiu_ddrc.c
+++ b/sim/bfin/dv-bfin_ebiu_ddrc.c
@@ -68,6 +68,10 @@ bfin_ebiu_ddrc_io_write_buffer (struct hw *me, const void *source,
   bu32 *value32p;
   void *valuep;
 
+  /* Invalid access mode is higher priority than missing register.  */
+  if (!dv_bfin_mmr_require_16_32 (me, addr, nr_bytes, true))
+    return 0;
+
   if (nr_bytes == 4)
     value = dv_load_4 (source);
   else
@@ -84,11 +88,13 @@ bfin_ebiu_ddrc_io_write_buffer (struct hw *me, const void *source,
     {
     case mmr_offset(errmst):
     case mmr_offset(rstctl):
-      dv_bfin_mmr_require_16 (me, addr, nr_bytes, true);
+      if (!dv_bfin_mmr_require_16 (me, addr, nr_bytes, true))
+	return 0;
       *value16p = value;
       break;
     default:
-      dv_bfin_mmr_require_32 (me, addr, nr_bytes, true);
+      if (!dv_bfin_mmr_require_32 (me, addr, nr_bytes, true))
+	return 0;
       *value32p = value;
       break;
     }
@@ -106,6 +112,10 @@ bfin_ebiu_ddrc_io_read_buffer (struct hw *me, void *dest,
   bu16 *value16p;
   void *valuep;
 
+  /* Invalid access mode is higher priority than missing register.  */
+  if (!dv_bfin_mmr_require_16_32 (me, addr, nr_bytes, true))
+    return 0;
+
   mmr_off = addr - ddrc->base;
   valuep = (void *)((unsigned long)ddrc + mmr_base() + mmr_off);
   value16p = valuep;
@@ -117,11 +127,13 @@ bfin_ebiu_ddrc_io_read_buffer (struct hw *me, void *dest,
     {
     case mmr_offset(errmst):
     case mmr_offset(rstctl):
-      dv_bfin_mmr_require_16 (me, addr, nr_bytes, false);
+      if (!dv_bfin_mmr_require_16 (me, addr, nr_bytes, false))
+	return 0;
       dv_store_2 (dest, *value16p);
       break;
     default:
-      dv_bfin_mmr_require_32 (me, addr, nr_bytes, false);
+      if (!dv_bfin_mmr_require_32 (me, addr, nr_bytes, false))
+	return 0;
       dv_store_4 (dest, *value32p);
       break;
     }
diff --git a/sim/bfin/dv-bfin_ebiu_sdc.c b/sim/bfin/dv-bfin_ebiu_sdc.c
index e7a036a..396b1e4 100644
--- a/sim/bfin/dv-bfin_ebiu_sdc.c
+++ b/sim/bfin/dv-bfin_ebiu_sdc.c
@@ -56,6 +56,10 @@ bfin_ebiu_sdc_io_write_buffer (struct hw *me, const void *source,
   bu32 *value32p;
   void *valuep;
 
+  /* Invalid access mode is higher priority than missing register.  */
+  if (!dv_bfin_mmr_require_16_32 (me, addr, nr_bytes, true))
+    return 0;
+
   if (nr_bytes == 4)
     value = dv_load_4 (source);
   else
@@ -77,21 +81,25 @@ bfin_ebiu_sdc_io_write_buffer (struct hw *me, const void *source,
     case mmr_offset(sdbctl):
       if (sdc->type == 561)
 	{
-	  dv_bfin_mmr_require_32 (me, addr, nr_bytes, true);
+	  if (!dv_bfin_mmr_require_32 (me, addr, nr_bytes, true))
+	    return 0;
 	  *value32p = value;
 	}
       else
 	{
-	  dv_bfin_mmr_require_16 (me, addr, nr_bytes, true);
+	  if (!dv_bfin_mmr_require_16 (me, addr, nr_bytes, true))
+	    return 0;
 	  *value16p = value;
 	}
       break;
     case mmr_offset(sdrrc):
-      dv_bfin_mmr_require_16 (me, addr, nr_bytes, true);
+      if (!dv_bfin_mmr_require_16 (me, addr, nr_bytes, true))
+	return 0;
       *value16p = value;
       break;
     case mmr_offset(sdstat):
-      dv_bfin_mmr_require_16 (me, addr, nr_bytes, true);
+      if (!dv_bfin_mmr_require_16 (me, addr, nr_bytes, true))
+	return 0;
       /* XXX: Some bits are W1C ...  */
       break;
     }
@@ -109,6 +117,10 @@ bfin_ebiu_sdc_io_read_buffer (struct hw *me, void *dest,
   bu16 *value16p;
   void *valuep;
 
+  /* Invalid access mode is higher priority than missing register.  */
+  if (!dv_bfin_mmr_require_16_32 (me, addr, nr_bytes, false))
+    return 0;
+
   mmr_off = addr - sdc->base;
   valuep = (void *)((unsigned long)sdc + mmr_base() + mmr_off);
   value16p = valuep;
@@ -124,18 +136,21 @@ bfin_ebiu_sdc_io_read_buffer (struct hw *me, void *dest,
     case mmr_offset(sdbctl):
       if (sdc->type == 561)
 	{
-	  dv_bfin_mmr_require_32 (me, addr, nr_bytes, false);
+	  if (!dv_bfin_mmr_require_32 (me, addr, nr_bytes, false))
+	    return 0;
 	  dv_store_4 (dest, *value32p);
 	}
       else
 	{
-	  dv_bfin_mmr_require_16 (me, addr, nr_bytes, false);
+	  if (!dv_bfin_mmr_require_16 (me, addr, nr_bytes, false))
+	    return 0;
 	  dv_store_2 (dest, *value16p);
 	}
       break;
     case mmr_offset(sdrrc):
     case mmr_offset(sdstat):
-      dv_bfin_mmr_require_16 (me, addr, nr_bytes, false);
+      if (!dv_bfin_mmr_require_16 (me, addr, nr_bytes, false))
+	return 0;
       dv_store_2 (dest, *value16p);
       break;
     }
diff --git a/sim/bfin/dv-bfin_emac.c b/sim/bfin/dv-bfin_emac.c
index 1abdf99..7bdedbb 100644
--- a/sim/bfin/dv-bfin_emac.c
+++ b/sim/bfin/dv-bfin_emac.c
@@ -177,8 +177,10 @@ bfin_emac_io_write_buffer (struct hw *me, const void *source,
   bu32 value;
   bu32 *valuep;
 
+  /* Invalid access mode is higher priority than missing register.  */
   /* XXX: 16bit accesses are allowed ...  */
-  dv_bfin_mmr_require_32 (me, addr, nr_bytes, true);
+  if (!dv_bfin_mmr_require_32 (me, addr, nr_bytes, true))
+    return 0;
   value = dv_load_4 (source);
 
   mmr_off = addr - emac->base;
@@ -263,7 +265,7 @@ bfin_emac_io_write_buffer (struct hw *me, const void *source,
       break;
     default:
       dv_bfin_mmr_invalid (me, addr, nr_bytes, true);
-      break;
+      return 0;
     }
 
   return nr_bytes;
@@ -277,8 +279,10 @@ bfin_emac_io_read_buffer (struct hw *me, void *dest,
   bu32 mmr_off;
   bu32 *valuep;
 
+  /* Invalid access mode is higher priority than missing register.  */
   /* XXX: 16bit accesses are allowed ...  */
-  dv_bfin_mmr_require_32 (me, addr, nr_bytes, false);
+  if (!dv_bfin_mmr_require_32 (me, addr, nr_bytes, false))
+    return 0;
 
   mmr_off = addr - emac->base;
   valuep = (void *)((unsigned long)emac + mmr_base() + mmr_off);
@@ -328,7 +332,7 @@ bfin_emac_io_read_buffer (struct hw *me, void *dest,
       break;
     default:
       dv_bfin_mmr_invalid (me, addr, nr_bytes, false);
-      break;
+      return 0;
     }
 
   return nr_bytes;
diff --git a/sim/bfin/dv-bfin_eppi.c b/sim/bfin/dv-bfin_eppi.c
index 5999568..5ca2a9c 100644
--- a/sim/bfin/dv-bfin_eppi.c
+++ b/sim/bfin/dv-bfin_eppi.c
@@ -90,6 +90,10 @@ bfin_eppi_io_write_buffer (struct hw *me, const void *source,
   bu32 *value32p;
   void *valuep;
 
+  /* Invalid access mode is higher priority than missing register.  */
+  if (!dv_bfin_mmr_require_16_32 (me, addr, nr_bytes, true))
+    return 0;
+
   if (nr_bytes == 4)
     value = dv_load_4 (source);
   else
@@ -105,7 +109,8 @@ bfin_eppi_io_write_buffer (struct hw *me, const void *source,
   switch (mmr_off)
     {
     case mmr_offset(status):
-      dv_bfin_mmr_require_16 (me, addr, nr_bytes, true);
+      if (!dv_bfin_mmr_require_16 (me, addr, nr_bytes, true))
+	return 0;
       dv_w1c_2 (value16p, value, 0x1ff);
       break;
     case mmr_offset(hcount):
@@ -115,7 +120,8 @@ bfin_eppi_io_write_buffer (struct hw *me, const void *source,
     case mmr_offset(frame):
     case mmr_offset(line):
     case mmr_offset(clkdiv):
-      dv_bfin_mmr_require_16 (me, addr, nr_bytes, true);
+      if (!dv_bfin_mmr_require_16 (me, addr, nr_bytes, true))
+	return 0;
       *value16p = value;
       break;
     case mmr_offset(control):
@@ -128,12 +134,13 @@ bfin_eppi_io_write_buffer (struct hw *me, const void *source,
     case mmr_offset(fs2p_lavf):
     case mmr_offset(clip):
     case mmr_offset(err):
-      dv_bfin_mmr_require_32 (me, addr, nr_bytes, true);
+      if (!dv_bfin_mmr_require_32 (me, addr, nr_bytes, true))
+	return 0;
       *value32p = value;
       break;
     default:
       dv_bfin_mmr_invalid (me, addr, nr_bytes, true);
-      break;
+      return 0;
     }
 
   return nr_bytes;
@@ -149,6 +156,10 @@ bfin_eppi_io_read_buffer (struct hw *me, void *dest,
   bu32 *value32p;
   void *valuep;
 
+  /* Invalid access mode is higher priority than missing register.  */
+  if (!dv_bfin_mmr_require_16_32 (me, addr, nr_bytes, true))
+    return 0;
+
   mmr_off = addr - eppi->base;
   valuep = (void *)((unsigned long)eppi + mmr_base() + mmr_off);
   value16p = valuep;
@@ -166,7 +177,8 @@ bfin_eppi_io_read_buffer (struct hw *me, void *dest,
     case mmr_offset(frame):
     case mmr_offset(line):
     case mmr_offset(clkdiv):
-      dv_bfin_mmr_require_16 (me, addr, nr_bytes, false);
+      if (!dv_bfin_mmr_require_16 (me, addr, nr_bytes, false))
+	return 0;
       dv_store_2 (dest, *value16p);
       break;
     case mmr_offset(control):
@@ -176,12 +188,13 @@ bfin_eppi_io_read_buffer (struct hw *me, void *dest,
     case mmr_offset(fs2p_lavf):
     case mmr_offset(clip):
     case mmr_offset(err):
-      dv_bfin_mmr_require_32 (me, addr, nr_bytes, false);
+      if (!dv_bfin_mmr_require_32 (me, addr, nr_bytes, false))
+	return 0;
       dv_store_4 (dest, *value32p);
       break;
     default:
       dv_bfin_mmr_invalid (me, addr, nr_bytes, false);
-      break;
+      return 0;
     }
 
   return nr_bytes;
diff --git a/sim/bfin/dv-bfin_evt.c b/sim/bfin/dv-bfin_evt.c
index 6f859b5..cb2d0df 100644
--- a/sim/bfin/dv-bfin_evt.c
+++ b/sim/bfin/dv-bfin_evt.c
@@ -50,6 +50,10 @@ bfin_evt_io_write_buffer (struct hw *me, const void *source,
   bu32 mmr_off;
   bu32 value;
 
+  /* Invalid access mode is higher priority than missing register.  */
+  if (!dv_bfin_mmr_require_32 (me, addr, nr_bytes, true))
+    return 0;
+
   value = dv_load_4 (source);
   mmr_off = addr - evt->base;
 
@@ -68,6 +72,10 @@ bfin_evt_io_read_buffer (struct hw *me, void *dest,
   bu32 mmr_off;
   bu32 value;
 
+  /* Invalid access mode is higher priority than missing register.  */
+  if (!dv_bfin_mmr_require_32 (me, addr, nr_bytes, false))
+    return 0;
+
   mmr_off = addr - evt->base;
 
   HW_TRACE_READ ();
diff --git a/sim/bfin/dv-bfin_gpio.c b/sim/bfin/dv-bfin_gpio.c
index 555d3f1..44c6e7a 100644
--- a/sim/bfin/dv-bfin_gpio.c
+++ b/sim/bfin/dv-bfin_gpio.c
@@ -110,14 +110,16 @@ bfin_gpio_io_write_buffer (struct hw *me, const void *source, int space,
   bu16 *valuep;
   bu32 data = port->data;
 
+  /* Invalid access mode is higher priority than missing register.  */
+  if (!dv_bfin_mmr_require_16 (me, addr, nr_bytes, true))
+    return 0;
+
   value = dv_load_2 (source);
   mmr_off = addr - port->base;
   valuep = (void *)((unsigned long)port + mmr_base() + mmr_off);
 
   HW_TRACE_WRITE ();
 
-  dv_bfin_mmr_require_16 (me, addr, nr_bytes, true);
-
   switch (mmr_off)
     {
     case mmr_offset(data):
@@ -153,7 +155,7 @@ bfin_gpio_io_write_buffer (struct hw *me, const void *source, int space,
       break;
     default:
       dv_bfin_mmr_invalid (me, addr, nr_bytes, true);
-      break;
+      return 0;
     }
 
   /* If updating masks, make sure we send updated port info.  */
@@ -182,13 +184,15 @@ bfin_gpio_io_read_buffer (struct hw *me, void *dest, int space,
   bu32 mmr_off;
   bu16 *valuep;
 
+  /* Invalid access mode is higher priority than missing register.  */
+  if (!dv_bfin_mmr_require_16 (me, addr, nr_bytes, false))
+    return 0;
+
   mmr_off = addr - port->base;
   valuep = (void *)((unsigned long)port + mmr_base() + mmr_off);
 
   HW_TRACE_READ ();
 
-  dv_bfin_mmr_require_16 (me, addr, nr_bytes, false);
-
   switch (mmr_off)
     {
     case mmr_offset(data):
@@ -218,7 +222,7 @@ bfin_gpio_io_read_buffer (struct hw *me, void *dest, int space,
       break;
     default:
       dv_bfin_mmr_invalid (me, addr, nr_bytes, false);
-      break;
+      return 0;
     }
 
   return nr_bytes;
diff --git a/sim/bfin/dv-bfin_gpio2.c b/sim/bfin/dv-bfin_gpio2.c
index 0069e0d..a2b9419 100644
--- a/sim/bfin/dv-bfin_gpio2.c
+++ b/sim/bfin/dv-bfin_gpio2.c
@@ -66,22 +66,28 @@ bfin_gpio_io_write_buffer (struct hw *me, const void *source, int space,
   bu32 *value32p;
   void *valuep;
 
+  mmr_off = addr - port->base;
+
+  /* Invalid access mode is higher priority than missing register.  */
+  if (mmr_off == mmr_offset (mux))
+    {
+      if (!dv_bfin_mmr_require_32 (me, addr, nr_bytes, true))
+	return 0;
+    }
+  else
+    if (!dv_bfin_mmr_require_16 (me, addr, nr_bytes, true))
+	return 0;
+
   if (nr_bytes == 4)
     value = dv_load_4 (source);
   else
     value = dv_load_2 (source);
-  mmr_off = addr - port->base;
   valuep = (void *)((unsigned long)port + mmr_base() + mmr_off);
   value16p = valuep;
   value32p = valuep;
 
   HW_TRACE_WRITE ();
 
-  if (mmr_off == mmr_offset (mux))
-    dv_bfin_mmr_require_32 (me, addr, nr_bytes, true);
-  else
-    dv_bfin_mmr_require_16 (me, addr, nr_bytes, true);
-
   switch (mmr_off)
     {
     case mmr_offset(fer):
@@ -108,7 +114,7 @@ bfin_gpio_io_write_buffer (struct hw *me, const void *source, int space,
       break;
     default:
       dv_bfin_mmr_invalid (me, addr, nr_bytes, true);
-      break;
+      return 0;
     }
 
   /* If tweaking output pins, make sure we send updated port info.  */
@@ -148,17 +154,23 @@ bfin_gpio_io_read_buffer (struct hw *me, void *dest, int space,
   void *valuep;
 
   mmr_off = addr - port->base;
+
+  /* Invalid access mode is higher priority than missing register.  */
+  if (mmr_off == mmr_offset (mux))
+    {
+      if (!dv_bfin_mmr_require_32 (me, addr, nr_bytes, false))
+	return 0;
+    }
+  else
+    if (!dv_bfin_mmr_require_16 (me, addr, nr_bytes, false))
+      return 0;
+
   valuep = (void *)((unsigned long)port + mmr_base() + mmr_off);
   value16p = valuep;
   value32p = valuep;
 
   HW_TRACE_READ ();
 
-  if (mmr_off == mmr_offset (mux))
-    dv_bfin_mmr_require_32 (me, addr, nr_bytes, false);
-  else
-    dv_bfin_mmr_require_16 (me, addr, nr_bytes, false);
-
   switch (mmr_off)
     {
     case mmr_offset(data):
@@ -179,7 +191,7 @@ bfin_gpio_io_read_buffer (struct hw *me, void *dest, int space,
       break;
     default:
       dv_bfin_mmr_invalid (me, addr, nr_bytes, false);
-      break;
+      return 0;
     }
 
   return nr_bytes;
diff --git a/sim/bfin/dv-bfin_gptimer.c b/sim/bfin/dv-bfin_gptimer.c
index 26f6a34..e4c05ca 100644
--- a/sim/bfin/dv-bfin_gptimer.c
+++ b/sim/bfin/dv-bfin_gptimer.c
@@ -61,6 +61,10 @@ bfin_gptimer_io_write_buffer (struct hw *me, const void *source, int space,
   bu32 *value32p;
   void *valuep;
 
+  /* Invalid access mode is higher priority than missing register.  */
+  if (!dv_bfin_mmr_require_16_32 (me, addr, nr_bytes, true))
+    return 0;
+
   if (nr_bytes == 4)
     value = dv_load_4 (source);
   else
@@ -76,18 +80,20 @@ bfin_gptimer_io_write_buffer (struct hw *me, const void *source, int space,
   switch (mmr_off)
     {
     case mmr_offset(config):
-      dv_bfin_mmr_require_16 (me, addr, nr_bytes, true);
+      if (!dv_bfin_mmr_require_16 (me, addr, nr_bytes, true))
+	return 0;
       *value16p = value;
       break;
     case mmr_offset(counter):
     case mmr_offset(period):
     case mmr_offset(width):
-      dv_bfin_mmr_require_32 (me, addr, nr_bytes, true);
+      if (!dv_bfin_mmr_require_32 (me, addr, nr_bytes, true))
+	return 0;
       *value32p = value;
       break;
     default:
       dv_bfin_mmr_invalid (me, addr, nr_bytes, true);
-      break;
+      return 0;
     }
 
   return nr_bytes;
@@ -103,6 +109,10 @@ bfin_gptimer_io_read_buffer (struct hw *me, void *dest, int space,
   bu32 *value32p;
   void *valuep;
 
+  /* Invalid access mode is higher priority than missing register.  */
+  if (!dv_bfin_mmr_require_16_32 (me, addr, nr_bytes, false))
+    return 0;
+
   mmr_off = addr - gptimer->base;
   valuep = (void *)((unsigned long)gptimer + mmr_base() + mmr_off);
   value16p = valuep;
@@ -113,18 +123,20 @@ bfin_gptimer_io_read_buffer (struct hw *me, void *dest, int space,
   switch (mmr_off)
     {
     case mmr_offset(config):
-      dv_bfin_mmr_require_16 (me, addr, nr_bytes, false);
+      if (!dv_bfin_mmr_require_16 (me, addr, nr_bytes, false))
+	return 0;
       dv_store_2 (dest, *value16p);
       break;
     case mmr_offset(counter):
     case mmr_offset(period):
     case mmr_offset(width):
-      dv_bfin_mmr_require_32 (me, addr, nr_bytes, false);
+      if (!dv_bfin_mmr_require_32 (me, addr, nr_bytes, false))
+	return 0;
       dv_store_4 (dest, *value32p);
       break;
     default:
       dv_bfin_mmr_invalid (me, addr, nr_bytes, false);
-      break;
+      return 0;
     }
 
   return nr_bytes;
diff --git a/sim/bfin/dv-bfin_jtag.c b/sim/bfin/dv-bfin_jtag.c
index 0f34c68..ad4c8b6 100644
--- a/sim/bfin/dv-bfin_jtag.c
+++ b/sim/bfin/dv-bfin_jtag.c
@@ -54,6 +54,10 @@ bfin_jtag_io_write_buffer (struct hw *me, const void *source, int space,
   bu32 value;
   bu32 *valuep;
 
+  /* Invalid access mode is higher priority than missing register.  */
+  if (!dv_bfin_mmr_require_32 (me, addr, nr_bytes, true))
+    return 0;
+
   value = dv_load_4 (source);
   mmr_off = addr - jtag->base;
   valuep = (void *)((unsigned long)jtag + mmr_base() + mmr_off);
@@ -70,7 +74,7 @@ bfin_jtag_io_write_buffer (struct hw *me, const void *source, int space,
       break;
     default:
       dv_bfin_mmr_invalid (me, addr, nr_bytes, true);
-      break;
+      return 0;
     }
 
   return nr_bytes;
@@ -85,6 +89,10 @@ bfin_jtag_io_read_buffer (struct hw *me, void *dest, int space,
   bu32 value;
   bu32 *valuep;
 
+  /* Invalid access mode is higher priority than missing register.  */
+  if (!dv_bfin_mmr_require_32 (me, addr, nr_bytes, false))
+    return 0;
+
   mmr_off = addr - jtag->base;
   valuep = (void *)((unsigned long)jtag + mmr_base() + mmr_off);
 
@@ -97,9 +105,8 @@ bfin_jtag_io_read_buffer (struct hw *me, void *dest, int space,
       value = *valuep;
       break;
     default:
-      while (1) /* Core MMRs -> exception -> doesn't return.  */
-	dv_bfin_mmr_invalid (me, addr, nr_bytes, false);
-      break;
+      dv_bfin_mmr_invalid (me, addr, nr_bytes, false);
+      return 0;
     }
 
   dv_store_4 (dest, value);
diff --git a/sim/bfin/dv-bfin_mmu.c b/sim/bfin/dv-bfin_mmu.c
index a3d5ba1..ce8cc9f 100644
--- a/sim/bfin/dv-bfin_mmu.c
+++ b/sim/bfin/dv-bfin_mmu.c
@@ -101,6 +101,10 @@ bfin_mmu_io_write_buffer (struct hw *me, const void *source,
   bu32 value;
   bu32 *valuep;
 
+  /* Invalid access mode is higher priority than missing register.  */
+  if (!dv_bfin_mmr_require_32 (me, addr, nr_bytes, true))
+    return 0;
+
   value = dv_load_4 (source);
 
   mmr_off = addr - mmu->base;
@@ -159,7 +163,7 @@ bfin_mmu_io_write_buffer (struct hw *me, const void *source,
       break;
     default:
       dv_bfin_mmr_invalid (me, addr, nr_bytes, true);
-      break;
+      return 0;
     }
 
   return nr_bytes;
@@ -173,6 +177,10 @@ bfin_mmu_io_read_buffer (struct hw *me, void *dest,
   bu32 mmr_off;
   bu32 *valuep;
 
+  /* Invalid access mode is higher priority than missing register.  */
+  if (!dv_bfin_mmr_require_32 (me, addr, nr_bytes, false))
+    return 0;
+
   mmr_off = addr - mmu->base;
   valuep = (void *)((unsigned long)mmu + mmr_base() + mmr_off);
 
@@ -200,9 +208,8 @@ bfin_mmu_io_read_buffer (struct hw *me, void *dest,
       dv_store_4 (dest, *valuep);
       break;
     default:
-      while (1) /* Core MMRs -> exception -> doesn't return.  */
-	dv_bfin_mmr_invalid (me, addr, nr_bytes, false);
-      break;
+      dv_bfin_mmr_invalid (me, addr, nr_bytes, false);
+      return 0;
     }
 
   return nr_bytes;
diff --git a/sim/bfin/dv-bfin_nfc.c b/sim/bfin/dv-bfin_nfc.c
index 478a682..288e251 100644
--- a/sim/bfin/dv-bfin_nfc.c
+++ b/sim/bfin/dv-bfin_nfc.c
@@ -77,14 +77,16 @@ bfin_nfc_io_write_buffer (struct hw *me, const void *source, int space,
   bu32 value;
   bu16 *valuep;
 
+  /* Invalid access mode is higher priority than missing register.  */
+  if (!dv_bfin_mmr_require_16 (me, addr, nr_bytes, true))
+    return 0;
+
   value = dv_load_2 (source);
   mmr_off = addr - nfc->base;
   valuep = (void *)((unsigned long)nfc + mmr_base() + mmr_off);
 
   HW_TRACE_WRITE ();
 
-  dv_bfin_mmr_require_16 (me, addr, nr_bytes, true);
-
   switch (mmr_off)
     {
     case mmr_offset(ctl):
@@ -112,7 +114,7 @@ bfin_nfc_io_write_buffer (struct hw *me, const void *source, int space,
       break;
     default:
       dv_bfin_mmr_invalid (me, addr, nr_bytes, true);
-      break;
+      return 0;
     }
 
   return nr_bytes;
@@ -126,13 +128,15 @@ bfin_nfc_io_read_buffer (struct hw *me, void *dest, int space,
   bu32 mmr_off;
   bu16 *valuep;
 
+  /* Invalid access mode is higher priority than missing register.  */
+  if (!dv_bfin_mmr_require_16 (me, addr, nr_bytes, false))
+    return 0;
+
   mmr_off = addr - nfc->base;
   valuep = (void *)((unsigned long)nfc + mmr_base() + mmr_off);
 
   HW_TRACE_READ ();
 
-  dv_bfin_mmr_require_16 (me, addr, nr_bytes, false);
-
   switch (mmr_off)
     {
     case mmr_offset(ctl):
@@ -156,7 +160,7 @@ bfin_nfc_io_read_buffer (struct hw *me, void *dest, int space,
       /* These regs are write only.  */
     default:
       dv_bfin_mmr_invalid (me, addr, nr_bytes, false);
-      break;
+      return 0;
     }
 
   return nr_bytes;
diff --git a/sim/bfin/dv-bfin_otp.c b/sim/bfin/dv-bfin_otp.c
index 52bcf47..4a20eb1 100644
--- a/sim/bfin/dv-bfin_otp.c
+++ b/sim/bfin/dv-bfin_otp.c
@@ -104,6 +104,10 @@ bfin_otp_io_write_buffer (struct hw *me, const void *source, int space,
   bu32 *value32p;
   void *valuep;
 
+  /* Invalid access mode is higher priority than missing register.  */
+  if (!dv_bfin_mmr_require_16_32 (me, addr, nr_bytes, true))
+    return 0;
+
   if (nr_bytes == 4)
     value = dv_load_4 (source);
   else
@@ -122,7 +126,8 @@ bfin_otp_io_write_buffer (struct hw *me, const void *source, int space,
       {
 	int page;
 
-	dv_bfin_mmr_require_16 (me, addr, nr_bytes, true);
+	if (!dv_bfin_mmr_require_16 (me, addr, nr_bytes, true))
+	  return 0;
 	/* XXX: Seems like these bits aren't writable.  */
 	*value16p = value & 0x39FF;
 
@@ -142,12 +147,14 @@ bfin_otp_io_write_buffer (struct hw *me, const void *source, int space,
 	break;
       }
     case mmr_offset(ben):
-      dv_bfin_mmr_require_16 (me, addr, nr_bytes, true);
+      if (!dv_bfin_mmr_require_16 (me, addr, nr_bytes, true))
+	return 0;
       /* XXX: All bits seem to be writable.  */
       *value16p = value;
       break;
     case mmr_offset(status):
-      dv_bfin_mmr_require_16 (me, addr, nr_bytes, true);
+      if (!dv_bfin_mmr_require_16 (me, addr, nr_bytes, true))
+	return 0;
       /* XXX: All bits seem to be W1C.  */
       dv_w1c_2 (value16p, value, -1);
       break;
@@ -156,12 +163,13 @@ bfin_otp_io_write_buffer (struct hw *me, const void *source, int space,
     case mmr_offset(data1):
     case mmr_offset(data2):
     case mmr_offset(data3):
-      dv_bfin_mmr_require_32 (me, addr, nr_bytes, true);
+      if (!dv_bfin_mmr_require_32 (me, addr, nr_bytes, true))
+	return 0;
       *value32p = value;
       break;
     default:
       dv_bfin_mmr_invalid (me, addr, nr_bytes, true);
-      break;
+      return 0;
     }
 
   return nr_bytes;
@@ -177,6 +185,10 @@ bfin_otp_io_read_buffer (struct hw *me, void *dest, int space,
   bu32 *value32p;
   void *valuep;
 
+  /* Invalid access mode is higher priority than missing register.  */
+  if (!dv_bfin_mmr_require_16_32 (me, addr, nr_bytes, false))
+    return 0;
+
   mmr_off = addr - otp->base;
   valuep = (void *)((unsigned long)otp + mmr_base() + mmr_off);
   value16p = valuep;
@@ -189,7 +201,8 @@ bfin_otp_io_read_buffer (struct hw *me, void *dest, int space,
     case mmr_offset(control):
     case mmr_offset(ben):
     case mmr_offset(status):
-      dv_bfin_mmr_require_16 (me, addr, nr_bytes, false);
+      if (!dv_bfin_mmr_require_16 (me, addr, nr_bytes, false))
+	return 0;
       dv_store_2 (dest, *value16p);
       break;
     case mmr_offset(timing):
@@ -197,12 +210,13 @@ bfin_otp_io_read_buffer (struct hw *me, void *dest, int space,
     case mmr_offset(data1):
     case mmr_offset(data2):
     case mmr_offset(data3):
-      dv_bfin_mmr_require_32 (me, addr, nr_bytes, false);
+      if (!dv_bfin_mmr_require_32 (me, addr, nr_bytes, false))
+	return 0;
       dv_store_4 (dest, *value32p);
       break;
     default:
       dv_bfin_mmr_invalid (me, addr, nr_bytes, false);
-      break;
+      return 0;
     }
 
   return nr_bytes;
diff --git a/sim/bfin/dv-bfin_pfmon.c b/sim/bfin/dv-bfin_pfmon.c
index 05eff5f..f97d5079 100644
--- a/sim/bfin/dv-bfin_pfmon.c
+++ b/sim/bfin/dv-bfin_pfmon.c
@@ -53,6 +53,10 @@ bfin_pfmon_io_write_buffer (struct hw *me, const void *source, int space,
   bu32 value;
   bu32 *valuep;
 
+  /* Invalid access mode is higher priority than missing register.  */
+  if (!dv_bfin_mmr_require_32 (me, addr, nr_bytes, true))
+    return 0;
+
   value = dv_load_4 (source);
   mmr_off = addr - pfmon->base;
   valuep = (void *)((unsigned long)pfmon + mmr_base() + mmr_off);
@@ -68,7 +72,7 @@ bfin_pfmon_io_write_buffer (struct hw *me, const void *source, int space,
       break;
     default:
       dv_bfin_mmr_invalid (me, addr, nr_bytes, true);
-      break;
+      return 0;
     }
 
   return nr_bytes;
@@ -83,6 +87,10 @@ bfin_pfmon_io_read_buffer (struct hw *me, void *dest, int space,
   bu32 value;
   bu32 *valuep;
 
+  /* Invalid access mode is higher priority than missing register.  */
+  if (!dv_bfin_mmr_require_32 (me, addr, nr_bytes, false))
+    return 0;
+
   mmr_off = addr - pfmon->base;
   valuep = (void *)((unsigned long)pfmon + mmr_base() + mmr_off);
 
@@ -96,9 +104,8 @@ bfin_pfmon_io_read_buffer (struct hw *me, void *dest, int space,
       value = *valuep;
       break;
     default:
-      while (1) /* Core MMRs -> exception -> doesn't return.  */
-	dv_bfin_mmr_invalid (me, addr, nr_bytes, false);
-      break;
+      dv_bfin_mmr_invalid (me, addr, nr_bytes, false);
+      return 0;
     }
 
   dv_store_4 (dest, value);
diff --git a/sim/bfin/dv-bfin_pint.c b/sim/bfin/dv-bfin_pint.c
index a6b83ec..4eadf9b 100644
--- a/sim/bfin/dv-bfin_pint.c
+++ b/sim/bfin/dv-bfin_pint.c
@@ -63,6 +63,11 @@ bfin_pint_io_write_buffer (struct hw *me, const void *source, int space,
   bu32 value;
   bu32 *valuep;
 
+  /* Invalid access mode is higher priority than missing register.  */
+  /* XXX: The hardware allows 16 or 32 bit accesses ...  */
+  if (!dv_bfin_mmr_require_32 (me, addr, nr_bytes, true))
+    return 0;
+
   if (nr_bytes == 4)
     value = dv_load_4 (source);
   else
@@ -72,9 +77,6 @@ bfin_pint_io_write_buffer (struct hw *me, const void *source, int space,
 
   HW_TRACE_WRITE ();
 
-  /* XXX: The hardware allows 16 or 32 bit accesses ...  */
-  dv_bfin_mmr_require_32 (me, addr, nr_bytes, true);
-
   switch (mmr_off)
     {
     case mmr_offset(request):
@@ -103,7 +105,7 @@ bfin_pint_io_write_buffer (struct hw *me, const void *source, int space,
       break;
     default:
       dv_bfin_mmr_invalid (me, addr, nr_bytes, true);
-      break;
+      return 0;
     }
 
 #if 0
@@ -134,14 +136,16 @@ bfin_pint_io_read_buffer (struct hw *me, void *dest, int space,
   bu32 mmr_off;
   bu32 *valuep;
 
+  /* Invalid access mode is higher priority than missing register.  */
+  /* XXX: The hardware allows 16 or 32 bit accesses ...  */
+  if (!dv_bfin_mmr_require_32 (me, addr, nr_bytes, false))
+    return 0;
+
   mmr_off = addr - pint->base;
   valuep = (void *)((unsigned long)pint + mmr_base() + mmr_off);
 
   HW_TRACE_READ ();
 
-  /* XXX: The hardware allows 16 or 32 bit accesses ...  */
-  dv_bfin_mmr_require_32 (me, addr, nr_bytes, false);
-
   switch (mmr_off)
     {
     case mmr_offset(request):
@@ -164,7 +168,7 @@ bfin_pint_io_read_buffer (struct hw *me, void *dest, int space,
       break;
     default:
       dv_bfin_mmr_invalid (me, addr, nr_bytes, false);
-      break;
+      return 0;
     }
 
   return nr_bytes;
diff --git a/sim/bfin/dv-bfin_pll.c b/sim/bfin/dv-bfin_pll.c
index 7729180..304d01a 100644
--- a/sim/bfin/dv-bfin_pll.c
+++ b/sim/bfin/dv-bfin_pll.c
@@ -59,6 +59,10 @@ bfin_pll_io_write_buffer (struct hw *me, const void *source,
   bu32 *value32p;
   void *valuep;
 
+  /* Invalid access mode is higher priority than missing register.  */
+  if (!dv_bfin_mmr_require_16_32 (me, addr, nr_bytes, true))
+    return 0;
+
   if (nr_bytes == 4)
     value = dv_load_4 (source);
   else
@@ -74,12 +78,14 @@ bfin_pll_io_write_buffer (struct hw *me, const void *source,
   switch (mmr_off)
     {
     case mmr_offset(pll_stat):
-      dv_bfin_mmr_require_16 (me, addr, nr_bytes, true);
+      if (!dv_bfin_mmr_require_16 (me, addr, nr_bytes, true))
+	return 0;
     case mmr_offset(chipid):
       /* Discard writes.  */
       break;
     default:
-      dv_bfin_mmr_require_16 (me, addr, nr_bytes, true);
+      if (!dv_bfin_mmr_require_16 (me, addr, nr_bytes, true))
+	return 0;
       *value16p = value;
       break;
     }
@@ -97,6 +103,10 @@ bfin_pll_io_read_buffer (struct hw *me, void *dest,
   bu16 *value16p;
   void *valuep;
 
+  /* Invalid access mode is higher priority than missing register.  */
+  if (!dv_bfin_mmr_require_16_32 (me, addr, nr_bytes, false))
+    return 0;
+
   mmr_off = addr - pll->base;
   valuep = (void *)((unsigned long)pll + mmr_base() + mmr_off);
   value16p = valuep;
@@ -110,7 +120,8 @@ bfin_pll_io_read_buffer (struct hw *me, void *dest,
       dv_store_4 (dest, *value32p);
       break;
     default:
-      dv_bfin_mmr_require_16 (me, addr, nr_bytes, false);
+      if (!dv_bfin_mmr_require_16 (me, addr, nr_bytes, false))
+	return 0;
       dv_store_2 (dest, *value16p);
       break;
     }
diff --git a/sim/bfin/dv-bfin_ppi.c b/sim/bfin/dv-bfin_ppi.c
index eadcfdb..7014e9a 100644
--- a/sim/bfin/dv-bfin_ppi.c
+++ b/sim/bfin/dv-bfin_ppi.c
@@ -85,14 +85,16 @@ bfin_ppi_io_write_buffer (struct hw *me, const void *source, int space,
   bu32 value;
   bu16 *valuep;
 
+  /* Invalid access mode is higher priority than missing register.  */
+  if (!dv_bfin_mmr_require_16 (me, addr, nr_bytes, true))
+    return 0;
+
   value = dv_load_2 (source);
   mmr_off = addr - ppi->base;
   valuep = (void *)((unsigned long)ppi + mmr_base() + mmr_off);
 
   HW_TRACE_WRITE ();
 
-  dv_bfin_mmr_require_16 (me, addr, nr_bytes, true);
-
   switch (mmr_off)
     {
     case mmr_offset(control):
@@ -109,7 +111,7 @@ bfin_ppi_io_write_buffer (struct hw *me, const void *source, int space,
       break;
     default:
       dv_bfin_mmr_invalid (me, addr, nr_bytes, true);
-      break;
+      return 0;
     }
 
   return nr_bytes;
@@ -123,13 +125,15 @@ bfin_ppi_io_read_buffer (struct hw *me, void *dest, int space,
   bu32 mmr_off;
   bu16 *valuep;
 
+  /* Invalid access mode is higher priority than missing register.  */
+  if (!dv_bfin_mmr_require_16 (me, addr, nr_bytes, false))
+    return 0;
+
   mmr_off = addr - ppi->base;
   valuep = (void *)((unsigned long)ppi + mmr_base() + mmr_off);
 
   HW_TRACE_READ ();
 
-  dv_bfin_mmr_require_16 (me, addr, nr_bytes, false);
-
   switch (mmr_off)
     {
     case mmr_offset(control):
@@ -141,7 +145,7 @@ bfin_ppi_io_read_buffer (struct hw *me, void *dest, int space,
       break;
     default:
       dv_bfin_mmr_invalid (me, addr, nr_bytes, false);
-      break;
+      return 0;
     }
 
   return nr_bytes;
diff --git a/sim/bfin/dv-bfin_rtc.c b/sim/bfin/dv-bfin_rtc.c
index d2220ca..49b6216 100644
--- a/sim/bfin/dv-bfin_rtc.c
+++ b/sim/bfin/dv-bfin_rtc.c
@@ -61,6 +61,10 @@ bfin_rtc_io_write_buffer (struct hw *me, const void *source,
   bu32 *value32p;
   void *valuep;
 
+  /* Invalid access mode is higher priority than missing register.  */
+  if (!dv_bfin_mmr_require_16_32 (me, addr, nr_bytes, true))
+    return 0;
+
   if (nr_bytes == 4)
     value = dv_load_4 (source);
   else
@@ -104,6 +108,10 @@ bfin_rtc_io_read_buffer (struct hw *me, void *dest,
   bu32 *value32p;
   void *valuep;
 
+  /* Invalid access mode is higher priority than missing register.  */
+  if (!dv_bfin_mmr_require_16_32 (me, addr, nr_bytes, false))
+    return 0;
+
   mmr_off = addr - rtc->base;
   valuep = (void *)((unsigned long)rtc + mmr_base() + mmr_off);
   value16p = valuep;
diff --git a/sim/bfin/dv-bfin_sic.c b/sim/bfin/dv-bfin_sic.c
index 3978543..3518581 100644
--- a/sim/bfin/dv-bfin_sic.c
+++ b/sim/bfin/dv-bfin_sic.c
@@ -150,6 +150,10 @@ bfin_sic_52x_io_write_buffer (struct hw *me, const void *source, int space,
   bu32 *value32p;
   void *valuep;
 
+  /* Invalid access mode is higher priority than missing register.  */
+  if (!dv_bfin_mmr_require_16_32 (me, addr, nr_bytes, true))
+    return 0;
+
   if (nr_bytes == 4)
     value = dv_load_4 (source);
   else
@@ -204,6 +208,10 @@ bfin_sic_52x_io_read_buffer (struct hw *me, void *dest, int space,
   bu32 *value32p;
   void *valuep;
 
+  /* Invalid access mode is higher priority than missing register.  */
+  if (!dv_bfin_mmr_require_16_32 (me, addr, nr_bytes, false))
+    return 0;
+
   mmr_off = addr - sic->base;
   valuep = (void *)((unsigned long)sic + mmr_base() + mmr_off);
   value16p = valuep;
@@ -256,6 +264,10 @@ bfin_sic_537_io_write_buffer (struct hw *me, const void *source, int space,
   bu32 *value32p;
   void *valuep;
 
+  /* Invalid access mode is higher priority than missing register.  */
+  if (!dv_bfin_mmr_require_16_32 (me, addr, nr_bytes, true))
+    return 0;
+
   if (nr_bytes == 4)
     value = dv_load_4 (source);
   else
@@ -309,6 +321,10 @@ bfin_sic_537_io_read_buffer (struct hw *me, void *dest, int space,
   bu32 *value32p;
   void *valuep;
 
+  /* Invalid access mode is higher priority than missing register.  */
+  if (!dv_bfin_mmr_require_16_32 (me, addr, nr_bytes, false))
+    return 0;
+
   mmr_off = addr - sic->base;
   valuep = (void *)((unsigned long)sic + mmr_base() + mmr_off);
   value16p = valuep;
@@ -362,6 +378,10 @@ bfin_sic_54x_io_write_buffer (struct hw *me, const void *source, int space,
   bu32 *value32p;
   void *valuep;
 
+  /* Invalid access mode is higher priority than missing register.  */
+  if (!dv_bfin_mmr_require_16_32 (me, addr, nr_bytes, true))
+    return 0;
+
   if (nr_bytes == 4)
     value = dv_load_4 (source);
   else
@@ -412,6 +432,10 @@ bfin_sic_54x_io_read_buffer (struct hw *me, void *dest, int space,
   bu32 *value32p;
   void *valuep;
 
+  /* Invalid access mode is higher priority than missing register.  */
+  if (!dv_bfin_mmr_require_16_32 (me, addr, nr_bytes, false))
+    return 0;
+
   mmr_off = addr - sic->base;
   valuep = (void *)((unsigned long)sic + mmr_base() + mmr_off);
   value16p = valuep;
@@ -461,6 +485,10 @@ bfin_sic_561_io_write_buffer (struct hw *me, const void *source, int space,
   bu32 *value32p;
   void *valuep;
 
+  /* Invalid access mode is higher priority than missing register.  */
+  if (!dv_bfin_mmr_require_16_32 (me, addr, nr_bytes, true))
+    return 0;
+
   if (nr_bytes == 4)
     value = dv_load_4 (source);
   else
@@ -515,6 +543,10 @@ bfin_sic_561_io_read_buffer (struct hw *me, void *dest, int space,
   bu32 *value32p;
   void *valuep;
 
+  /* Invalid access mode is higher priority than missing register.  */
+  if (!dv_bfin_mmr_require_16_32 (me, addr, nr_bytes, false))
+    return 0;
+
   mmr_off = addr - sic->base;
   valuep = (void *)((unsigned long)sic + mmr_base() + mmr_off);
   value16p = valuep;
diff --git a/sim/bfin/dv-bfin_spi.c b/sim/bfin/dv-bfin_spi.c
index 56a8f93..b4c68ca 100644
--- a/sim/bfin/dv-bfin_spi.c
+++ b/sim/bfin/dv-bfin_spi.c
@@ -77,14 +77,16 @@ bfin_spi_io_write_buffer (struct hw *me, const void *source, int space,
   bu32 value;
   bu16 *valuep;
 
+  /* Invalid access mode is higher priority than missing register.  */
+  if (!dv_bfin_mmr_require_16 (me, addr, nr_bytes, true))
+    return 0;
+
   value = dv_load_2 (source);
   mmr_off = addr - spi->base;
   valuep = (void *)((unsigned long)spi + mmr_base() + mmr_off);
 
   HW_TRACE_WRITE ();
 
-  dv_bfin_mmr_require_16 (me, addr, nr_bytes, true);
-
   switch (mmr_off)
     {
     case mmr_offset(stat):
@@ -107,7 +109,7 @@ bfin_spi_io_write_buffer (struct hw *me, const void *source, int space,
       break;
     default:
       dv_bfin_mmr_invalid (me, addr, nr_bytes, true);
-      break;
+      return 0;
     }
 
   return nr_bytes;
@@ -121,13 +123,15 @@ bfin_spi_io_read_buffer (struct hw *me, void *dest, int space,
   bu32 mmr_off;
   bu16 *valuep;
 
+  /* Invalid access mode is higher priority than missing register.  */
+  if (!dv_bfin_mmr_require_16 (me, addr, nr_bytes, false))
+    return 0;
+
   mmr_off = addr - spi->base;
   valuep = (void *)((unsigned long)spi + mmr_base() + mmr_off);
 
   HW_TRACE_READ ();
 
-  dv_bfin_mmr_require_16 (me, addr, nr_bytes, false);
-
   switch (mmr_off)
     {
     case mmr_offset(rdbr):
@@ -145,7 +149,7 @@ bfin_spi_io_read_buffer (struct hw *me, void *dest, int space,
       break;
     default:
       dv_bfin_mmr_invalid (me, addr, nr_bytes, false);
-      break;
+      return 0;
     }
 
   return nr_bytes;
diff --git a/sim/bfin/dv-bfin_trace.c b/sim/bfin/dv-bfin_trace.c
index 8358224..b6bed4d 100644
--- a/sim/bfin/dv-bfin_trace.c
+++ b/sim/bfin/dv-bfin_trace.c
@@ -80,6 +80,10 @@ bfin_trace_io_write_buffer (struct hw *me, const void *source,
   bu32 mmr_off;
   bu32 value;
 
+  /* Invalid access mode is higher priority than missing register.  */
+  if (!dv_bfin_mmr_require_32 (me, addr, nr_bytes, true))
+    return 0;
+
   value = dv_load_4 (source);
   mmr_off = addr - trace->base;
 
@@ -96,7 +100,7 @@ bfin_trace_io_write_buffer (struct hw *me, const void *source,
       break;
     default:
       dv_bfin_mmr_invalid (me, addr, nr_bytes, true);
-      break;
+      return 0;
     }
 
   return nr_bytes;
@@ -110,6 +114,10 @@ bfin_trace_io_read_buffer (struct hw *me, void *dest,
   bu32 mmr_off;
   bu32 value;
 
+  /* Invalid access mode is higher priority than missing register.  */
+  if (!dv_bfin_mmr_require_32 (me, addr, nr_bytes, false))
+    return 0;
+
   mmr_off = addr - trace->base;
 
   HW_TRACE_READ ();
@@ -148,9 +156,8 @@ bfin_trace_io_read_buffer (struct hw *me, void *dest,
 	break;
       }
     default:
-      while (1) /* Core MMRs -> exception -> doesn't return.  */
-	dv_bfin_mmr_invalid (me, addr, nr_bytes, false);
-      break;
+      dv_bfin_mmr_invalid (me, addr, nr_bytes, false);
+      return 0;
     }
 
   dv_store_4 (dest, value);
diff --git a/sim/bfin/dv-bfin_twi.c b/sim/bfin/dv-bfin_twi.c
index e1b4cde..6ceb7f9 100644
--- a/sim/bfin/dv-bfin_twi.c
+++ b/sim/bfin/dv-bfin_twi.c
@@ -81,14 +81,16 @@ bfin_twi_io_write_buffer (struct hw *me, const void *source, int space,
   bu32 value;
   bu16 *valuep;
 
+  /* Invalid access mode is higher priority than missing register.  */
+  if (!dv_bfin_mmr_require_16 (me, addr, nr_bytes, true))
+    return 0;
+
   value = dv_load_2 (source);
   mmr_off = addr - twi->base;
   valuep = (void *)((unsigned long)twi + mmr_base() + mmr_off);
 
   HW_TRACE_WRITE ();
 
-  dv_bfin_mmr_require_16 (me, addr, nr_bytes, true);
-
   switch (mmr_off)
     {
     case mmr_offset(clkdiv):
@@ -120,7 +122,7 @@ bfin_twi_io_write_buffer (struct hw *me, const void *source, int space,
       break;
     default:
       dv_bfin_mmr_invalid (me, addr, nr_bytes, true);
-      break;
+      return 0;
     }
 
   return nr_bytes;
@@ -134,13 +136,15 @@ bfin_twi_io_read_buffer (struct hw *me, void *dest, int space,
   bu32 mmr_off;
   bu16 *valuep;
 
+  /* Invalid access mode is higher priority than missing register.  */
+  if (!dv_bfin_mmr_require_16 (me, addr, nr_bytes, false))
+    return 0;
+
   mmr_off = addr - twi->base;
   valuep = (void *)((unsigned long)twi + mmr_base() + mmr_off);
 
   HW_TRACE_READ ();
 
-  dv_bfin_mmr_require_16 (me, addr, nr_bytes, false);
-
   switch (mmr_off)
     {
     case mmr_offset(clkdiv):
@@ -168,7 +172,7 @@ bfin_twi_io_read_buffer (struct hw *me, void *dest, int space,
       break;
     default:
       dv_bfin_mmr_invalid (me, addr, nr_bytes, false);
-      break;
+      return 0;
     }
 
   return nr_bytes;
diff --git a/sim/bfin/dv-bfin_uart.c b/sim/bfin/dv-bfin_uart.c
index 0460ca5..10cf7e1 100644
--- a/sim/bfin/dv-bfin_uart.c
+++ b/sim/bfin/dv-bfin_uart.c
@@ -138,14 +138,16 @@ bfin_uart_io_write_buffer (struct hw *me, const void *source,
   bu32 value;
   bu16 *valuep;
 
+  /* Invalid access mode is higher priority than missing register.  */
+  if (!dv_bfin_mmr_require_16 (me, addr, nr_bytes, true))
+    return 0;
+
   value = dv_load_2 (source);
   mmr_off = addr - uart->base;
   valuep = (void *)((unsigned long)uart + mmr_base() + mmr_off);
 
   HW_TRACE_WRITE ();
 
-  dv_bfin_mmr_require_16 (me, addr, nr_bytes, true);
-
   /* XXX: All MMRs are "8bit" ... what happens to high 8bits ?  */
   switch (mmr_off)
     {
@@ -181,7 +183,7 @@ bfin_uart_io_write_buffer (struct hw *me, const void *source,
       break;
     default:
       dv_bfin_mmr_invalid (me, addr, nr_bytes, true);
-      break;
+      return 0;
     }
 
   return nr_bytes;
@@ -260,13 +262,15 @@ bfin_uart_io_read_buffer (struct hw *me, void *dest,
   bu32 mmr_off;
   bu16 *valuep;
 
+  /* Invalid access mode is higher priority than missing register.  */
+  if (!dv_bfin_mmr_require_16 (me, addr, nr_bytes, false))
+    return 0;
+
   mmr_off = addr - uart->base;
   valuep = (void *)((unsigned long)uart + mmr_base() + mmr_off);
 
   HW_TRACE_READ ();
 
-  dv_bfin_mmr_require_16 (me, addr, nr_bytes, false);
-
   switch (mmr_off)
     {
     case mmr_offset(dll):
@@ -300,7 +304,7 @@ bfin_uart_io_read_buffer (struct hw *me, void *dest,
       break;
     default:
       dv_bfin_mmr_invalid (me, addr, nr_bytes, false);
-      break;
+      return 0;
     }
 
   return nr_bytes;
diff --git a/sim/bfin/dv-bfin_uart2.c b/sim/bfin/dv-bfin_uart2.c
index 40a7edd..59716b9 100644
--- a/sim/bfin/dv-bfin_uart2.c
+++ b/sim/bfin/dv-bfin_uart2.c
@@ -76,14 +76,16 @@ bfin_uart_io_write_buffer (struct hw *me, const void *source,
   bu32 value;
   bu16 *valuep;
 
+  /* Invalid access mode is higher priority than missing register.  */
+  if (!dv_bfin_mmr_require_16 (me, addr, nr_bytes, true))
+    return 0;
+
   value = dv_load_2 (source);
   mmr_off = addr - uart->base;
   valuep = (void *)((unsigned long)uart + mmr_base() + mmr_off);
 
   HW_TRACE_WRITE ();
 
-  dv_bfin_mmr_require_16 (me, addr, nr_bytes, true);
-
   /* XXX: All MMRs are "8bit" ... what happens to high 8bits ?  */
 
   switch (mmr_off)
@@ -118,7 +120,7 @@ bfin_uart_io_write_buffer (struct hw *me, const void *source,
       break;
     default:
       dv_bfin_mmr_invalid (me, addr, nr_bytes, true);
-      break;
+      return 0;
     }
 
   return nr_bytes;
@@ -132,13 +134,15 @@ bfin_uart_io_read_buffer (struct hw *me, void *dest,
   bu32 mmr_off;
   bu16 *valuep;
 
+  /* Invalid access mode is higher priority than missing register.  */
+  if (!dv_bfin_mmr_require_16 (me, addr, nr_bytes, false))
+    return 0;
+
   mmr_off = addr - uart->base;
   valuep = (void *)((unsigned long)uart + mmr_base() + mmr_off);
 
   HW_TRACE_READ ();
 
-  dv_bfin_mmr_require_16 (me, addr, nr_bytes, false);
-
   switch (mmr_off)
     {
     case mmr_offset(rbr):
@@ -165,7 +169,7 @@ bfin_uart_io_read_buffer (struct hw *me, void *dest,
       break;
     default:
       dv_bfin_mmr_invalid (me, addr, nr_bytes, false);
-      break;
+      return 0;
     }
 
   return nr_bytes;
diff --git a/sim/bfin/dv-bfin_wdog.c b/sim/bfin/dv-bfin_wdog.c
index d34bfa1..53d1692 100644
--- a/sim/bfin/dv-bfin_wdog.c
+++ b/sim/bfin/dv-bfin_wdog.c
@@ -61,6 +61,10 @@ bfin_wdog_io_write_buffer (struct hw *me, const void *source,
   bu32 *value32p;
   void *valuep;
 
+  /* Invalid access mode is higher priority than missing register.  */
+  if (!dv_bfin_mmr_require_16_32 (me, addr, nr_bytes, true))
+    return 0;
+
   if (nr_bytes == 4)
     value = dv_load_4 (source);
   else
@@ -111,6 +115,10 @@ bfin_wdog_io_read_buffer (struct hw *me, void *dest,
   bu32 *value32p;
   void *valuep;
 
+  /* Invalid access mode is higher priority than missing register.  */
+  if (!dv_bfin_mmr_require_16_32 (me, addr, nr_bytes, false))
+    return 0;
+
   mmr_off = addr - wdog->base;
   valuep = (void *)((unsigned long)wdog + mmr_base() + mmr_off);
   value16p = valuep;
@@ -121,7 +129,8 @@ bfin_wdog_io_read_buffer (struct hw *me, void *dest,
   switch (mmr_off)
     {
     case mmr_offset(ctl):
-      dv_bfin_mmr_require_16 (me, addr, nr_bytes, false);
+      if (!dv_bfin_mmr_require_16 (me, addr, nr_bytes, false))
+	return 0;
       dv_store_2 (dest, *value16p);
       break;
 
diff --git a/sim/bfin/dv-bfin_wp.c b/sim/bfin/dv-bfin_wp.c
index 5292cb2..17dc979 100644
--- a/sim/bfin/dv-bfin_wp.c
+++ b/sim/bfin/dv-bfin_wp.c
@@ -77,6 +77,10 @@ bfin_wp_io_write_buffer (struct hw *me, const void *source, int space,
   bu32 value;
   bu32 *valuep;
 
+  /* Invalid access mode is higher priority than missing register.  */
+  if (!dv_bfin_mmr_require_32 (me, addr, nr_bytes, true))
+    return 0;
+
   value = dv_load_4 (source);
   mmr_off = addr - wp->base;
   valuep = (void *)((unsigned long)wp + mmr_base() + mmr_off);
@@ -99,7 +103,7 @@ bfin_wp_io_write_buffer (struct hw *me, const void *source, int space,
       break;
     default:
       dv_bfin_mmr_invalid (me, addr, nr_bytes, true);
-      break;
+      return 0;
     }
 
   return nr_bytes;
@@ -114,6 +118,10 @@ bfin_wp_io_read_buffer (struct hw *me, void *dest, int space,
   bu32 value;
   bu32 *valuep;
 
+  /* Invalid access mode is higher priority than missing register.  */
+  if (!dv_bfin_mmr_require_32 (me, addr, nr_bytes, false))
+    return 0;
+
   mmr_off = addr - wp->base;
   valuep = (void *)((unsigned long)wp + mmr_base() + mmr_off);
 
@@ -131,9 +139,8 @@ bfin_wp_io_read_buffer (struct hw *me, void *dest, int space,
       value = *valuep;
       break;
     default:
-      while (1) /* Core MMRs -> exception -> doesn't return.  */
-	dv_bfin_mmr_invalid (me, addr, nr_bytes, false);
-      break;
+      dv_bfin_mmr_invalid (me, addr, nr_bytes, false);
+      return 0;
     }
 
   dv_store_4 (dest, value);
diff --git a/sim/bfin/tconfig.h b/sim/bfin/tconfig.h
deleted file mode 100644
index 3ecd174..0000000
--- a/sim/bfin/tconfig.h
+++ /dev/null
@@ -1,5 +0,0 @@
-/* Blackfin target configuration file.  -*- C -*- */
-
-/* We use this so that we are passed the requesting CPU for HW acesses.
-   Common sim core by default sets hw_system_cpu to NULL for WITH_HW.  */
-#define WITH_DEVICES 1