ptimer: Rename PTIMER_POLICY_DEFAULT to PTIMER_POLICY_LEGACY

The traditional ptimer behaviour includes a collection of weird edge
case behaviours.  In 2016 we improved the ptimer implementation to
fix these and generally make the behaviour more flexible, with
ptimers opting in to the new behaviour by passing an appropriate set
of policy flags to ptimer_init().  For backwards-compatibility, we
defined PTIMER_POLICY_DEFAULT (which sets no flags) to give the old
weird behaviour.

This turns out to be a poor choice of name, because people writing
new devices which use ptimers are misled into thinking that the
default is probably a sensible choice of flags, when in fact it is
almost always not what you want.  Rename PTIMER_POLICY_DEFAULT to
PTIMER_POLICY_LEGACY and beef up the comment to more clearly say that
new devices should not be using it.

The code-change part of this commit was produced by
  sed -i -e 's/PTIMER_POLICY_DEFAULT/PTIMER_POLICY_LEGACY/g' $(git grep -l PTIMER_POLICY_DEFAULT)
with the exception of a test name string change in
tests/unit/ptimer-test.c which was added manually.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Francisco Iglesias <francisco.iglesias@amd.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20220516103058.162280-1-peter.maydell@linaro.org

25 files changed, 44 insertions, 36 deletions

diff --git a/hw/arm/musicpal.c b/hw/arm/musicpal.c
index 7c840fb..b65c020 100644
--- a/hw/arm/musicpal.c
+++ b/hw/arm/musicpal.c
@@ -464,7 +464,7 @@ static void mv88w8618_timer_init(SysBusDevice *dev, mv88w8618_timer_state *s,
     sysbus_init_irq(dev, &s->irq);
     s->freq = freq;
 
-    s->ptimer = ptimer_init(mv88w8618_timer_tick, s, PTIMER_POLICY_DEFAULT);
+    s->ptimer = ptimer_init(mv88w8618_timer_tick, s, PTIMER_POLICY_LEGACY);
 }
 
 static uint64_t mv88w8618_pit_read(void *opaque, hwaddr offset,
diff --git a/hw/dma/xilinx_axidma.c b/hw/dma/xilinx_axidma.c
index bc383f5..cbb8f0f 100644
--- a/hw/dma/xilinx_axidma.c
+++ b/hw/dma/xilinx_axidma.c
@@ -552,7 +552,7 @@ static void xilinx_axidma_realize(DeviceState *dev, Error **errp)
 
         st->dma = s;
         st->nr = i;
-        st->ptimer = ptimer_init(timer_hit, st, PTIMER_POLICY_DEFAULT);
+        st->ptimer = ptimer_init(timer_hit, st, PTIMER_POLICY_LEGACY);
         ptimer_transaction_begin(st->ptimer);
         ptimer_set_freq(st->ptimer, s->freqhz);
         ptimer_transaction_commit(st->ptimer);
diff --git a/hw/dma/xlnx_csu_dma.c b/hw/dma/xlnx_csu_dma.c
index 60ada32..1ce52ea 100644
--- a/hw/dma/xlnx_csu_dma.c
+++ b/hw/dma/xlnx_csu_dma.c
@@ -666,7 +666,7 @@ static void xlnx_csu_dma_realize(DeviceState *dev, Error **errp)
     sysbus_init_irq(SYS_BUS_DEVICE(dev), &s->irq);
 
     s->src_timer = ptimer_init(xlnx_csu_dma_src_timeout_hit,
-                               s, PTIMER_POLICY_DEFAULT);
+                               s, PTIMER_POLICY_LEGACY);
 
     s->attr = MEMTXATTRS_UNSPECIFIED;
 
diff --git a/hw/m68k/mcf5206.c b/hw/m68k/mcf5206.c
index 6d93d76..2ab1b4f 100644
--- a/hw/m68k/mcf5206.c
+++ b/hw/m68k/mcf5206.c
@@ -152,7 +152,7 @@ static m5206_timer_state *m5206_timer_init(qemu_irq irq)
     m5206_timer_state *s;
 
     s = g_new0(m5206_timer_state, 1);
-    s->timer = ptimer_init(m5206_timer_trigger, s, PTIMER_POLICY_DEFAULT);
+    s->timer = ptimer_init(m5206_timer_trigger, s, PTIMER_POLICY_LEGACY);
     s->irq = irq;
     m5206_timer_reset(s);
     return s;
diff --git a/hw/m68k/mcf5208.c b/hw/m68k/mcf5208.c
index 655207e..be1033f 100644
--- a/hw/m68k/mcf5208.c
+++ b/hw/m68k/mcf5208.c
@@ -197,7 +197,7 @@ static void mcf5208_sys_init(MemoryRegion *address_space, qemu_irq *pic)
     /* Timers.  */
     for (i = 0; i < 2; i++) {
         s = g_new0(m5208_timer_state, 1);
-        s->timer = ptimer_init(m5208_timer_trigger, s, PTIMER_POLICY_DEFAULT);
+        s->timer = ptimer_init(m5208_timer_trigger, s, PTIMER_POLICY_LEGACY);
         memory_region_init_io(&s->iomem, NULL, &m5208_timer_ops, s,
                               "m5208-timer", 0x00004000);
         memory_region_add_subregion(address_space, 0xfc080000 + 0x4000 * i,
diff --git a/hw/net/can/xlnx-zynqmp-can.c b/hw/net/can/xlnx-zynqmp-can.c
index 22bb891..82ac48c 100644
--- a/hw/net/can/xlnx-zynqmp-can.c
+++ b/hw/net/can/xlnx-zynqmp-can.c
@@ -1079,7 +1079,7 @@ static void xlnx_zynqmp_can_realize(DeviceState *dev, Error **errp)
 
     /* Allocate a new timer. */
     s->can_timer = ptimer_init(xlnx_zynqmp_can_ptimer_cb, s,
-                               PTIMER_POLICY_DEFAULT);
+                               PTIMER_POLICY_LEGACY);
 
     ptimer_transaction_begin(s->can_timer);
 
diff --git a/hw/net/fsl_etsec/etsec.c b/hw/net/fsl_etsec/etsec.c
index 6d50c39..4e6cc70 100644
--- a/hw/net/fsl_etsec/etsec.c
+++ b/hw/net/fsl_etsec/etsec.c
@@ -393,7 +393,7 @@ static void etsec_realize(DeviceState *dev, Error **errp)
                               object_get_typename(OBJECT(dev)), dev->id, etsec);
     qemu_format_nic_info_str(qemu_get_queue(etsec->nic), etsec->conf.macaddr.a);
 
-    etsec->ptimer = ptimer_init(etsec_timer_hit, etsec, PTIMER_POLICY_DEFAULT);
+    etsec->ptimer = ptimer_init(etsec_timer_hit, etsec, PTIMER_POLICY_LEGACY);
     ptimer_transaction_begin(etsec->ptimer);
     ptimer_set_freq(etsec->ptimer, 100);
     ptimer_transaction_commit(etsec->ptimer);
diff --git a/hw/net/lan9118.c b/hw/net/lan9118.c
index 6aff424..456ae38 100644
--- a/hw/net/lan9118.c
+++ b/hw/net/lan9118.c
@@ -1363,7 +1363,7 @@ static void lan9118_realize(DeviceState *dev, Error **errp)
     s->pmt_ctrl = 1;
     s->txp = &s->tx_packet;
 
-    s->timer = ptimer_init(lan9118_tick, s, PTIMER_POLICY_DEFAULT);
+    s->timer = ptimer_init(lan9118_tick, s, PTIMER_POLICY_LEGACY);
     ptimer_transaction_begin(s->timer);
     ptimer_set_freq(s->timer, 10000);
     ptimer_set_limit(s->timer, 0xffff, 1);
diff --git a/hw/rtc/exynos4210_rtc.c b/hw/rtc/exynos4210_rtc.c
index ae67641..d1620c7 100644
--- a/hw/rtc/exynos4210_rtc.c
+++ b/hw/rtc/exynos4210_rtc.c
@@ -564,14 +564,14 @@ static void exynos4210_rtc_init(Object *obj)
     Exynos4210RTCState *s = EXYNOS4210_RTC(obj);
     SysBusDevice *dev = SYS_BUS_DEVICE(obj);
 
-    s->ptimer = ptimer_init(exynos4210_rtc_tick, s, PTIMER_POLICY_DEFAULT);
+    s->ptimer = ptimer_init(exynos4210_rtc_tick, s, PTIMER_POLICY_LEGACY);
     ptimer_transaction_begin(s->ptimer);
     ptimer_set_freq(s->ptimer, RTC_BASE_FREQ);
     exynos4210_rtc_update_freq(s, 0);
     ptimer_transaction_commit(s->ptimer);
 
     s->ptimer_1Hz = ptimer_init(exynos4210_rtc_1Hz_tick,
-                                s, PTIMER_POLICY_DEFAULT);
+                                s, PTIMER_POLICY_LEGACY);
     ptimer_transaction_begin(s->ptimer_1Hz);
     ptimer_set_freq(s->ptimer_1Hz, RTC_BASE_FREQ);
     ptimer_transaction_commit(s->ptimer_1Hz);
diff --git a/hw/timer/allwinner-a10-pit.c b/hw/timer/allwinner-a10-pit.c
index c3fc2a4..971f784 100644
--- a/hw/timer/allwinner-a10-pit.c
+++ b/hw/timer/allwinner-a10-pit.c
@@ -275,7 +275,7 @@ static void a10_pit_init(Object *obj)
 
         tc->container = s;
         tc->index = i;
-        s->timer[i] = ptimer_init(a10_pit_timer_cb, tc, PTIMER_POLICY_DEFAULT);
+        s->timer[i] = ptimer_init(a10_pit_timer_cb, tc, PTIMER_POLICY_LEGACY);
     }
 }
 
diff --git a/hw/timer/altera_timer.c b/hw/timer/altera_timer.c
index c6e02d2..0f1f542 100644
--- a/hw/timer/altera_timer.c
+++ b/hw/timer/altera_timer.c
@@ -185,7 +185,7 @@ static void altera_timer_realize(DeviceState *dev, Error **errp)
         return;
     }
 
-    t->ptimer = ptimer_init(timer_hit, t, PTIMER_POLICY_DEFAULT);
+    t->ptimer = ptimer_init(timer_hit, t, PTIMER_POLICY_LEGACY);
     ptimer_transaction_begin(t->ptimer);
     ptimer_set_freq(t->ptimer, t->freq_hz);
     ptimer_transaction_commit(t->ptimer);
diff --git a/hw/timer/arm_timer.c b/hw/timer/arm_timer.c
index 84cf272..69c8863 100644
--- a/hw/timer/arm_timer.c
+++ b/hw/timer/arm_timer.c
@@ -180,7 +180,7 @@ static arm_timer_state *arm_timer_init(uint32_t freq)
     s->freq = freq;
     s->control = TIMER_CTRL_IE;
 
-    s->timer = ptimer_init(arm_timer_tick, s, PTIMER_POLICY_DEFAULT);
+    s->timer = ptimer_init(arm_timer_tick, s, PTIMER_POLICY_LEGACY);
     vmstate_register(NULL, VMSTATE_INSTANCE_ID_ANY, &vmstate_arm_timer, s);
     return s;
 }
diff --git a/hw/timer/digic-timer.c b/hw/timer/digic-timer.c
index e3aae4a..d5186f4 100644
--- a/hw/timer/digic-timer.c
+++ b/hw/timer/digic-timer.c
@@ -139,7 +139,7 @@ static void digic_timer_init(Object *obj)
 {
     DigicTimerState *s = DIGIC_TIMER(obj);
 
-    s->ptimer = ptimer_init(digic_timer_tick, NULL, PTIMER_POLICY_DEFAULT);
+    s->ptimer = ptimer_init(digic_timer_tick, NULL, PTIMER_POLICY_LEGACY);
 
     /*
      * FIXME: there is no documentation on Digic timer
diff --git a/hw/timer/etraxfs_timer.c b/hw/timer/etraxfs_timer.c
index 139e5b8..ecc2831 100644
--- a/hw/timer/etraxfs_timer.c
+++ b/hw/timer/etraxfs_timer.c
@@ -370,9 +370,9 @@ static void etraxfs_timer_realize(DeviceState *dev, Error **errp)
     ETRAXTimerState *t = ETRAX_TIMER(dev);
     SysBusDevice *sbd = SYS_BUS_DEVICE(dev);
 
-    t->ptimer_t0 = ptimer_init(timer0_hit, t, PTIMER_POLICY_DEFAULT);
-    t->ptimer_t1 = ptimer_init(timer1_hit, t, PTIMER_POLICY_DEFAULT);
-    t->ptimer_wd = ptimer_init(watchdog_hit, t, PTIMER_POLICY_DEFAULT);
+    t->ptimer_t0 = ptimer_init(timer0_hit, t, PTIMER_POLICY_LEGACY);
+    t->ptimer_t1 = ptimer_init(timer1_hit, t, PTIMER_POLICY_LEGACY);
+    t->ptimer_wd = ptimer_init(watchdog_hit, t, PTIMER_POLICY_LEGACY);
 
     sysbus_init_irq(sbd, &t->irq);
     sysbus_init_irq(sbd, &t->nmi);
diff --git a/hw/timer/exynos4210_mct.c b/hw/timer/exynos4210_mct.c
index d0e5343..e175a9f 100644
--- a/hw/timer/exynos4210_mct.c
+++ b/hw/timer/exynos4210_mct.c
@@ -1503,17 +1503,17 @@ static void exynos4210_mct_init(Object *obj)
 
     /* Global timer */
     s->g_timer.ptimer_frc = ptimer_init(exynos4210_gfrc_event, s,
-                                        PTIMER_POLICY_DEFAULT);
+                                        PTIMER_POLICY_LEGACY);
     memset(&s->g_timer.reg, 0, sizeof(struct gregs));
 
     /* Local timers */
     for (i = 0; i < 2; i++) {
         s->l_timer[i].tick_timer.ptimer_tick =
             ptimer_init(exynos4210_ltick_event, &s->l_timer[i],
-                        PTIMER_POLICY_DEFAULT);
+                        PTIMER_POLICY_LEGACY);
         s->l_timer[i].ptimer_frc =
             ptimer_init(exynos4210_lfrc_event, &s->l_timer[i],
-                        PTIMER_POLICY_DEFAULT);
+                        PTIMER_POLICY_LEGACY);
         s->l_timer[i].id = i;
     }
 
diff --git a/hw/timer/exynos4210_pwm.c b/hw/timer/exynos4210_pwm.c
index 2200881..02924a9 100644
--- a/hw/timer/exynos4210_pwm.c
+++ b/hw/timer/exynos4210_pwm.c
@@ -400,7 +400,7 @@ static void exynos4210_pwm_init(Object *obj)
         sysbus_init_irq(dev, &s->timer[i].irq);
         s->timer[i].ptimer = ptimer_init(exynos4210_pwm_tick,
                                          &s->timer[i],
-                                         PTIMER_POLICY_DEFAULT);
+                                         PTIMER_POLICY_LEGACY);
         s->timer[i].id = i;
         s->timer[i].parent = s;
     }
diff --git a/hw/timer/grlib_gptimer.c b/hw/timer/grlib_gptimer.c
index d511890..5c4923c 100644
--- a/hw/timer/grlib_gptimer.c
+++ b/hw/timer/grlib_gptimer.c
@@ -383,7 +383,7 @@ static void grlib_gptimer_realize(DeviceState *dev, Error **errp)
 
         timer->unit   = unit;
         timer->ptimer = ptimer_init(grlib_gptimer_hit, timer,
-                                    PTIMER_POLICY_DEFAULT);
+                                    PTIMER_POLICY_LEGACY);
         timer->id     = i;
 
         /* One IRQ line for each timer */
diff --git a/hw/timer/imx_epit.c b/hw/timer/imx_epit.c
index ebd5825..2bf8c75 100644
--- a/hw/timer/imx_epit.c
+++ b/hw/timer/imx_epit.c
@@ -347,9 +347,9 @@ static void imx_epit_realize(DeviceState *dev, Error **errp)
                           0x00001000);
     sysbus_init_mmio(sbd, &s->iomem);
 
-    s->timer_reload = ptimer_init(imx_epit_reload, s, PTIMER_POLICY_DEFAULT);
+    s->timer_reload = ptimer_init(imx_epit_reload, s, PTIMER_POLICY_LEGACY);
 
-    s->timer_cmp = ptimer_init(imx_epit_cmp, s, PTIMER_POLICY_DEFAULT);
+    s->timer_cmp = ptimer_init(imx_epit_cmp, s, PTIMER_POLICY_LEGACY);
 }
 
 static void imx_epit_class_init(ObjectClass *klass, void *data)
diff --git a/hw/timer/imx_gpt.c b/hw/timer/imx_gpt.c
index 5c0d9a2..80b8302 100644
--- a/hw/timer/imx_gpt.c
+++ b/hw/timer/imx_gpt.c
@@ -505,7 +505,7 @@ static void imx_gpt_realize(DeviceState *dev, Error **errp)
                           0x00001000);
     sysbus_init_mmio(sbd, &s->iomem);
 
-    s->timer = ptimer_init(imx_gpt_timeout, s, PTIMER_POLICY_DEFAULT);
+    s->timer = ptimer_init(imx_gpt_timeout, s, PTIMER_POLICY_LEGACY);
 }
 
 static void imx_gpt_class_init(ObjectClass *klass, void *data)
diff --git a/hw/timer/mss-timer.c b/hw/timer/mss-timer.c
index fe0ca90..ee7438f 100644
--- a/hw/timer/mss-timer.c
+++ b/hw/timer/mss-timer.c
@@ -232,7 +232,7 @@ static void mss_timer_init(Object *obj)
     for (i = 0; i < NUM_TIMERS; i++) {
         struct Msf2Timer *st = &t->timers[i];
 
-        st->ptimer = ptimer_init(timer_hit, st, PTIMER_POLICY_DEFAULT);
+        st->ptimer = ptimer_init(timer_hit, st, PTIMER_POLICY_LEGACY);
         ptimer_transaction_begin(st->ptimer);
         ptimer_set_freq(st->ptimer, t->freq_hz);
         ptimer_transaction_commit(st->ptimer);
diff --git a/hw/timer/sh_timer.c b/hw/timer/sh_timer.c
index c72c327..7788939 100644
--- a/hw/timer/sh_timer.c
+++ b/hw/timer/sh_timer.c
@@ -239,7 +239,7 @@ static void *sh_timer_init(uint32_t freq, int feat, qemu_irq irq)
     s->enabled = 0;
     s->irq = irq;
 
-    s->timer = ptimer_init(sh_timer_tick, s, PTIMER_POLICY_DEFAULT);
+    s->timer = ptimer_init(sh_timer_tick, s, PTIMER_POLICY_LEGACY);
 
     sh_timer_write(s, OFFSET_TCOR >> 2, s->tcor);
     sh_timer_write(s, OFFSET_TCNT >> 2, s->tcnt);
diff --git a/hw/timer/slavio_timer.c b/hw/timer/slavio_timer.c
index 90fdce4..8c4f6eb 100644
--- a/hw/timer/slavio_timer.c
+++ b/hw/timer/slavio_timer.c
@@ -405,7 +405,7 @@ static void slavio_timer_init(Object *obj)
         tc->timer_index = i;
 
         s->cputimer[i].timer = ptimer_init(slavio_timer_irq, tc,
-                                           PTIMER_POLICY_DEFAULT);
+                                           PTIMER_POLICY_LEGACY);
         ptimer_transaction_begin(s->cputimer[i].timer);
         ptimer_set_period(s->cputimer[i].timer, TIMER_PERIOD);
         ptimer_transaction_commit(s->cputimer[i].timer);
diff --git a/hw/timer/xilinx_timer.c b/hw/timer/xilinx_timer.c
index 1eb927e..c7f17cd 100644
--- a/hw/timer/xilinx_timer.c
+++ b/hw/timer/xilinx_timer.c
@@ -223,7 +223,7 @@ static void xilinx_timer_realize(DeviceState *dev, Error **errp)
 
         xt->parent = t;
         xt->nr = i;
-        xt->ptimer = ptimer_init(timer_hit, xt, PTIMER_POLICY_DEFAULT);
+        xt->ptimer = ptimer_init(timer_hit, xt, PTIMER_POLICY_LEGACY);
         ptimer_transaction_begin(xt->ptimer);
         ptimer_set_freq(xt->ptimer, t->freq_hz);
         ptimer_transaction_commit(xt->ptimer);
diff --git a/include/hw/ptimer.h b/include/hw/ptimer.h
index c443218..4dc02b0 100644
--- a/include/hw/ptimer.h
+++ b/include/hw/ptimer.h
@@ -33,9 +33,17 @@
  * to stderr when the guest attempts to enable the timer.
  */
 
-/* The default ptimer policy retains backward compatibility with the legacy
- * timers. Custom policies are adjusting the default one. Consider providing
- * a correct policy for your timer.
+/*
+ * The 'legacy' ptimer policy retains backward compatibility with the
+ * traditional ptimer behaviour from before policy flags were introduced.
+ * It has several weird behaviours which don't match typical hardware
+ * timer behaviour. For a new device using ptimers, you should not
+ * use PTIMER_POLICY_LEGACY, but instead check the actual behaviour
+ * that you need and specify the right set of policy flags to get that.
+ *
+ * If you are overhauling an existing device that uses PTIMER_POLICY_LEGACY
+ * and are in a position to check or test the real hardware behaviour,
+ * consider updating it to specify the right policy flags.
  *
  * The rough edges of the default policy:
  *  - Starting to run with a period = 0 emits error message and stops the
@@ -54,7 +62,7 @@
  *    since the last period, effectively restarting the timer with a
  *    counter = counter value at the moment of change (.i.e. one less).
  */
-#define PTIMER_POLICY_DEFAULT               0
+#define PTIMER_POLICY_LEGACY                0
 
 /* Periodic timer counter stays with "0" for a one period before wrapping
  * around.  */
diff --git a/tests/unit/ptimer-test.c b/tests/unit/ptimer-test.c
index 9176b96..a80ef5a 100644
--- a/tests/unit/ptimer-test.c
+++ b/tests/unit/ptimer-test.c
@@ -768,8 +768,8 @@ static void add_ptimer_tests(uint8_t policy)
     char policy_name[256] = "";
     char *tmp;
 
-    if (policy == PTIMER_POLICY_DEFAULT) {
-        g_sprintf(policy_name, "default");
+    if (policy == PTIMER_POLICY_LEGACY) {
+        g_sprintf(policy_name, "legacy");
     }
 
     if (policy & PTIMER_POLICY_WRAP_AFTER_ONE_PERIOD) {
@@ -862,7 +862,7 @@ static void add_ptimer_tests(uint8_t policy)
 static void add_all_ptimer_policies_comb_tests(void)
 {
     int last_policy = PTIMER_POLICY_TRIGGER_ONLY_ON_DECREMENT;
-    int policy = PTIMER_POLICY_DEFAULT;
+    int policy = PTIMER_POLICY_LEGACY;
 
     for (; policy < (last_policy << 1); policy++) {
         if ((policy & PTIMER_POLICY_TRIGGER_ONLY_ON_DECREMENT) &&