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 7c840fb428..b65c020115 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 bc383f53cc..cbb8f0f169 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 60ada3286b..1ce52ea5a2 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 6d93d761a5..2ab1b4f059 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 655207e393..be1033f84f 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 22bb8910fa..82ac48cee2 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 6d50c39543..4e6cc708de 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 6aff424cbe..456ae38107 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 ae67641de6..d1620c7a2a 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 c3fc2a4daa..971f78462a 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 c6e02d2b5a..0f1f54206a 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 84cf2726bb..69c8863472 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 e3aae4a45a..d5186f4454 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 139e5b86a4..ecc2831baf 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 d0e5343996..e175a9f5b9 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 220088120e..02924a9e5b 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 d511890109..5c4923c1e0 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 ebd58254d1..2bf8c754b2 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 5c0d9a269c..80b8302639 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 fe0ca905f3..ee7438f168 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 c72c327bfa..7788939766 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 90fdce4c44..8c4f6eb06b 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 1eb927eb84..c7f17cd646 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 c443218475..4dc02b0de4 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 9176b96c1c..a80ef5aff4 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) &&