sim: bfin: implement loop back support in the UARTs

The UART has a LOOP_ENA bit in its MCR register where writes to the THR
go to the RBR.  Implement support for this mode.

Signed-off-by: Mike Frysinger <vapier@gentoo.org>

1 files changed, 33 insertions, 19 deletions

diff --git a/sim/bfin/dv-bfin_uart.c b/sim/bfin/dv-bfin_uart.c
index f05ee15..697fa96 100644
--- a/sim/bfin/dv-bfin_uart.c
+++ b/sim/bfin/dv-bfin_uart.c
@@ -117,10 +117,21 @@ bfin_uart_reschedule (struct hw *me)
 }
 
 bu16
-bfin_uart_write_byte (struct hw *me, bu16 thr)
+bfin_uart_write_byte (struct hw *me, bu16 thr, bu16 mcr)
 {
+  struct bfin_uart *uart = hw_data (me);
   unsigned char ch = thr;
+
+  if (mcr & LOOP_ENA)
+    {
+      /* XXX: This probably doesn't work exactly right with
+              external FIFOs ...  */
+      uart->saved_byte = thr;
+      uart->saved_count = 1;
+    }
+
   bfin_uart_write_buffer (me, &ch, 1);
+
   return thr;
 }
 
@@ -149,7 +160,7 @@ bfin_uart_io_write_buffer (struct hw *me, const void *source,
 	uart->dll = value;
       else
 	{
-	  uart->thr = bfin_uart_write_byte (me, value);
+	  uart->thr = bfin_uart_write_byte (me, value, uart->mcr);
 
 	  if (uart->ier & ETBEI)
 	    hw_port_event (me, DV_PORT_TX, 1);
@@ -184,7 +195,7 @@ bfin_uart_io_write_buffer (struct hw *me, const void *source,
 
 /* Switch between socket and stdin on the fly.  */
 bu16
-bfin_uart_get_next_byte (struct hw *me, bu16 rbr, bool *fresh)
+bfin_uart_get_next_byte (struct hw *me, bu16 rbr, bu16 mcr, bool *fresh)
 {
   SIM_DESC sd = hw_system (me);
   struct bfin_uart *uart = hw_data (me);
@@ -197,23 +208,26 @@ bfin_uart_get_next_byte (struct hw *me, bu16 rbr, bool *fresh)
     fresh = &_fresh;
 
   *fresh = false;
-  if (status & DV_SOCKSER_DISCONNECTED)
+
+  if (uart->saved_count > 0)
+    {
+      *fresh = true;
+      rbr = uart->saved_byte;
+      --uart->saved_count;
+    }
+  else if (mcr & LOOP_ENA)
+    {
+      /* RX is disconnected, so only return local data.  */
+    }
+  else if (status & DV_SOCKSER_DISCONNECTED)
     {
-      if (uart->saved_count > 0)
+      char byte;
+      int ret = sim_io_poll_read (sd, 0/*STDIN*/, &byte, 1);
+
+      if (ret > 0)
 	{
 	  *fresh = true;
-	  rbr = uart->saved_byte;
-	  --uart->saved_count;
-	}
-      else
-	{
-	  char byte;
-	  int ret = sim_io_poll_read (sd, 0/*STDIN*/, &byte, 1);
-	  if (ret > 0)
-	    {
-	      *fresh = true;
-	      rbr = byte;
-	    }
+	  rbr = byte;
 	}
     }
   else
@@ -239,7 +253,7 @@ bfin_uart_get_status (struct hw *me)
     }
   else
     lsr |= (status & DV_SOCKSER_INPUT_EMPTY ? 0 : DR) |
-		 (status & DV_SOCKSER_OUTPUT_EMPTY ? TEMT | THRE : 0);
+	   (status & DV_SOCKSER_OUTPUT_EMPTY ? TEMT | THRE : 0);
 
   return lsr;
 }
@@ -266,7 +280,7 @@ bfin_uart_io_read_buffer (struct hw *me, void *dest,
 	dv_store_2 (dest, uart->dll);
       else
 	{
-	  uart->rbr = bfin_uart_get_next_byte (me, uart->rbr, NULL);
+	  uart->rbr = bfin_uart_get_next_byte (me, uart->rbr, uart->mcr, NULL);
 	  dv_store_2 (dest, uart->rbr);
 	}
       break;