hw/timer: Adding watchdog for NPCM7XX Timer.

The watchdog is part of NPCM7XX's timer module. Its behavior is
controlled by the WTCR register in the timer.

When enabled, the watchdog issues an interrupt signal after a pre-set
amount of cycles, and issues a reset signal shortly after that.

Reviewed-by: Tyrone Ting <kfting@nuvoton.com>
Signed-off-by: Hao Wu <wuhaotsh@google.com>
Signed-off-by: Havard Skinnemoen <hskinnemoen@google.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
[PMM: deleted blank line at end of npcm_watchdog_timer-test.c]
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

1 files changed, 220 insertions, 46 deletions

diff --git a/hw/timer/npcm7xx_timer.c b/hw/timer/npcm7xx_timer.c
index 2df9e3e..d24445b 100644
--- a/hw/timer/npcm7xx_timer.c
+++ b/hw/timer/npcm7xx_timer.c
@@ -17,6 +17,7 @@
 #include "qemu/osdep.h"
 
 #include "hw/irq.h"
+#include "hw/qdev-properties.h"
 #include "hw/misc/npcm7xx_clk.h"
 #include "hw/timer/npcm7xx_timer.h"
 #include "migration/vmstate.h"
@@ -60,6 +61,50 @@ enum NPCM7xxTimerRegisters {
 #define NPCM7XX_TCSR_PRESCALE_START     0
 #define NPCM7XX_TCSR_PRESCALE_LEN       8
 
+#define NPCM7XX_WTCR_WTCLK(rv)          extract32(rv, 10, 2)
+#define NPCM7XX_WTCR_FREEZE_EN          BIT(9)
+#define NPCM7XX_WTCR_WTE                BIT(7)
+#define NPCM7XX_WTCR_WTIE               BIT(6)
+#define NPCM7XX_WTCR_WTIS(rv)           extract32(rv, 4, 2)
+#define NPCM7XX_WTCR_WTIF               BIT(3)
+#define NPCM7XX_WTCR_WTRF               BIT(2)
+#define NPCM7XX_WTCR_WTRE               BIT(1)
+#define NPCM7XX_WTCR_WTR                BIT(0)
+
+/*
+ * The number of clock cycles between interrupt and reset in watchdog, used
+ * by the software to handle the interrupt before system is reset.
+ */
+#define NPCM7XX_WATCHDOG_INTERRUPT_TO_RESET_CYCLES 1024
+
+/* Start or resume the timer. */
+static void npcm7xx_timer_start(NPCM7xxBaseTimer *t)
+{
+    int64_t now;
+
+    now = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
+    t->expires_ns = now + t->remaining_ns;
+    timer_mod(&t->qtimer, t->expires_ns);
+}
+
+/* Stop counting. Record the time remaining so we can continue later. */
+static void npcm7xx_timer_pause(NPCM7xxBaseTimer *t)
+{
+    int64_t now;
+
+    timer_del(&t->qtimer);
+    now = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
+    t->remaining_ns = t->expires_ns - now;
+}
+
+/* Delete the timer and reset it to default state. */
+static void npcm7xx_timer_clear(NPCM7xxBaseTimer *t)
+{
+    timer_del(&t->qtimer);
+    t->expires_ns = 0;
+    t->remaining_ns = 0;
+}
+
 /*
  * Returns the index of timer in the tc->timer array. This can be used to
  * locate the registers that belong to this timer.
@@ -102,6 +147,52 @@ static uint32_t npcm7xx_timer_ns_to_count(NPCM7xxTimer *t, int64_t ns)
     return count;
 }
 
+static uint32_t npcm7xx_watchdog_timer_prescaler(const NPCM7xxWatchdogTimer *t)
+{
+    switch (NPCM7XX_WTCR_WTCLK(t->wtcr)) {
+    case 0:
+        return 1;
+    case 1:
+        return 256;
+    case 2:
+        return 2048;
+    case 3:
+        return 65536;
+    default:
+        g_assert_not_reached();
+    }
+}
+
+static void npcm7xx_watchdog_timer_reset_cycles(NPCM7xxWatchdogTimer *t,
+        int64_t cycles)
+{
+    uint32_t prescaler = npcm7xx_watchdog_timer_prescaler(t);
+    int64_t ns = (NANOSECONDS_PER_SECOND / NPCM7XX_TIMER_REF_HZ) * cycles;
+
+    /*
+     * The reset function always clears the current timer. The caller of the
+     * this needs to decide whether to start the watchdog timer based on
+     * specific flag in WTCR.
+     */
+    npcm7xx_timer_clear(&t->base_timer);
+
+    ns *= prescaler;
+    t->base_timer.remaining_ns = ns;
+}
+
+static void npcm7xx_watchdog_timer_reset(NPCM7xxWatchdogTimer *t)
+{
+    int64_t cycles = 1;
+    uint32_t s = NPCM7XX_WTCR_WTIS(t->wtcr);
+
+    g_assert(s <= 3);
+
+    cycles <<= NPCM7XX_WATCHDOG_BASETIME_SHIFT;
+    cycles <<= 2 * s;
+
+    npcm7xx_watchdog_timer_reset_cycles(t, cycles);
+}
+
 /*
  * Raise the interrupt line if there's a pending interrupt and interrupts are
  * enabled for this timer. If not, lower it.
@@ -116,16 +207,6 @@ static void npcm7xx_timer_check_interrupt(NPCM7xxTimer *t)
     trace_npcm7xx_timer_irq(DEVICE(tc)->canonical_path, index, pending);
 }
 
-/* Start or resume the timer. */
-static void npcm7xx_timer_start(NPCM7xxTimer *t)
-{
-    int64_t now;
-
-    now = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
-    t->expires_ns = now + t->remaining_ns;
-    timer_mod(&t->qtimer, t->expires_ns);
-}
-
 /*
  * Called when the counter reaches zero. Sets the interrupt flag, and either
  * restarts or disables the timer.
@@ -138,9 +219,9 @@ static void npcm7xx_timer_reached_zero(NPCM7xxTimer *t)
     tc->tisr |= BIT(index);
 
     if (t->tcsr & NPCM7XX_TCSR_PERIODIC) {
-        t->remaining_ns = npcm7xx_timer_count_to_ns(t, t->ticr);
+        t->base_timer.remaining_ns = npcm7xx_timer_count_to_ns(t, t->ticr);
         if (t->tcsr & NPCM7XX_TCSR_CEN) {
-            npcm7xx_timer_start(t);
+            npcm7xx_timer_start(&t->base_timer);
         }
     } else {
         t->tcsr &= ~(NPCM7XX_TCSR_CEN | NPCM7XX_TCSR_CACT);
@@ -149,15 +230,6 @@ static void npcm7xx_timer_reached_zero(NPCM7xxTimer *t)
     npcm7xx_timer_check_interrupt(t);
 }
 
-/* Stop counting. Record the time remaining so we can continue later. */
-static void npcm7xx_timer_pause(NPCM7xxTimer *t)
-{
-    int64_t now;
-
-    timer_del(&t->qtimer);
-    now = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
-    t->remaining_ns = t->expires_ns - now;
-}
 
 /*
  * Restart the timer from its initial value. If the timer was enabled and stays
@@ -167,10 +239,10 @@ static void npcm7xx_timer_pause(NPCM7xxTimer *t)
  */
 static void npcm7xx_timer_restart(NPCM7xxTimer *t, uint32_t old_tcsr)
 {
-    t->remaining_ns = npcm7xx_timer_count_to_ns(t, t->ticr);
+    t->base_timer.remaining_ns = npcm7xx_timer_count_to_ns(t, t->ticr);
 
     if (old_tcsr & t->tcsr & NPCM7XX_TCSR_CEN) {
-        npcm7xx_timer_start(t);
+        npcm7xx_timer_start(&t->base_timer);
     }
 }
 
@@ -181,10 +253,10 @@ static uint32_t npcm7xx_timer_read_tdr(NPCM7xxTimer *t)
     if (t->tcsr & NPCM7XX_TCSR_CEN) {
         int64_t now = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
 
-        return npcm7xx_timer_ns_to_count(t, t->expires_ns - now);
+        return npcm7xx_timer_ns_to_count(t, t->base_timer.expires_ns - now);
     }
 
-    return npcm7xx_timer_ns_to_count(t, t->remaining_ns);
+    return npcm7xx_timer_ns_to_count(t, t->base_timer.remaining_ns);
 }
 
 static void npcm7xx_timer_write_tcsr(NPCM7xxTimer *t, uint32_t new_tcsr)
@@ -216,9 +288,9 @@ static void npcm7xx_timer_write_tcsr(NPCM7xxTimer *t, uint32_t new_tcsr)
 
     if (npcm7xx_tcsr_prescaler(old_tcsr) != npcm7xx_tcsr_prescaler(new_tcsr)) {
         /* Recalculate time remaining based on the current TDR value. */
-        t->remaining_ns = npcm7xx_timer_count_to_ns(t, tdr);
+        t->base_timer.remaining_ns = npcm7xx_timer_count_to_ns(t, tdr);
         if (old_tcsr & t->tcsr & NPCM7XX_TCSR_CEN) {
-            npcm7xx_timer_start(t);
+            npcm7xx_timer_start(&t->base_timer);
         }
     }
 
@@ -232,11 +304,11 @@ static void npcm7xx_timer_write_tcsr(NPCM7xxTimer *t, uint32_t new_tcsr)
     if ((old_tcsr ^ new_tcsr) & NPCM7XX_TCSR_CEN) {
         if (new_tcsr & NPCM7XX_TCSR_CEN) {
             t->tcsr |= NPCM7XX_TCSR_CACT;
-            npcm7xx_timer_start(t);
+            npcm7xx_timer_start(&t->base_timer);
         } else {
             t->tcsr &= ~NPCM7XX_TCSR_CACT;
-            npcm7xx_timer_pause(t);
-            if (t->remaining_ns <= 0) {
+            npcm7xx_timer_pause(&t->base_timer);
+            if (t->base_timer.remaining_ns <= 0) {
                 npcm7xx_timer_reached_zero(t);
             }
         }
@@ -259,9 +331,47 @@ static void npcm7xx_timer_write_tisr(NPCM7xxTimerCtrlState *s, uint32_t value)
         if (value & (1U << i)) {
             npcm7xx_timer_check_interrupt(&s->timer[i]);
         }
+
     }
 }
 
+static void npcm7xx_timer_write_wtcr(NPCM7xxWatchdogTimer *t, uint32_t new_wtcr)
+{
+    uint32_t old_wtcr = t->wtcr;
+
+    /*
+     * WTIF and WTRF are cleared by writing 1. Writing 0 makes these bits
+     * unchanged.
+     */
+    if (new_wtcr & NPCM7XX_WTCR_WTIF) {
+        new_wtcr &= ~NPCM7XX_WTCR_WTIF;
+    } else if (old_wtcr & NPCM7XX_WTCR_WTIF) {
+        new_wtcr |= NPCM7XX_WTCR_WTIF;
+    }
+    if (new_wtcr & NPCM7XX_WTCR_WTRF) {
+        new_wtcr &= ~NPCM7XX_WTCR_WTRF;
+    } else if (old_wtcr & NPCM7XX_WTCR_WTRF) {
+        new_wtcr |= NPCM7XX_WTCR_WTRF;
+    }
+
+    t->wtcr = new_wtcr;
+
+    if (new_wtcr & NPCM7XX_WTCR_WTR) {
+        t->wtcr &= ~NPCM7XX_WTCR_WTR;
+        npcm7xx_watchdog_timer_reset(t);
+        if (new_wtcr & NPCM7XX_WTCR_WTE) {
+            npcm7xx_timer_start(&t->base_timer);
+        }
+    } else if ((old_wtcr ^ new_wtcr) & NPCM7XX_WTCR_WTE) {
+        if (new_wtcr & NPCM7XX_WTCR_WTE) {
+            npcm7xx_timer_start(&t->base_timer);
+        } else {
+            npcm7xx_timer_pause(&t->base_timer);
+        }
+    }
+
+}
+
 static hwaddr npcm7xx_tcsr_index(hwaddr reg)
 {
     switch (reg) {
@@ -353,7 +463,7 @@ static uint64_t npcm7xx_timer_read(void *opaque, hwaddr offset, unsigned size)
         break;
 
     case NPCM7XX_TIMER_WTCR:
-        value = s->wtcr;
+        value = s->watchdog_timer.wtcr;
         break;
 
     default:
@@ -409,8 +519,7 @@ static void npcm7xx_timer_write(void *opaque, hwaddr offset,
         return;
 
     case NPCM7XX_TIMER_WTCR:
-        qemu_log_mask(LOG_UNIMP, "%s: WTCR write not implemented: 0x%08x\n",
-                      __func__, value);
+        npcm7xx_timer_write_wtcr(&s->watchdog_timer, value);
         return;
     }
 
@@ -448,15 +557,42 @@ static void npcm7xx_timer_enter_reset(Object *obj, ResetType type)
     for (i = 0; i < NPCM7XX_TIMERS_PER_CTRL; i++) {
         NPCM7xxTimer *t = &s->timer[i];
 
-        timer_del(&t->qtimer);
-        t->expires_ns = 0;
-        t->remaining_ns = 0;
+        npcm7xx_timer_clear(&t->base_timer);
         t->tcsr = 0x00000005;
         t->ticr = 0x00000000;
     }
 
     s->tisr = 0x00000000;
-    s->wtcr = 0x00000400;
+    /*
+     * Set WTCLK to 1(default) and reset all flags except WTRF.
+     * WTRF is not reset during a core domain reset.
+     */
+    s->watchdog_timer.wtcr = 0x00000400 | (s->watchdog_timer.wtcr &
+            NPCM7XX_WTCR_WTRF);
+}
+
+static void npcm7xx_watchdog_timer_expired(void *opaque)
+{
+    NPCM7xxWatchdogTimer *t = opaque;
+
+    if (t->wtcr & NPCM7XX_WTCR_WTE) {
+        if (t->wtcr & NPCM7XX_WTCR_WTIF) {
+            if (t->wtcr & NPCM7XX_WTCR_WTRE) {
+                t->wtcr |= NPCM7XX_WTCR_WTRF;
+                /* send reset signal to CLK module*/
+                qemu_irq_raise(t->reset_signal);
+            }
+        } else {
+            t->wtcr |= NPCM7XX_WTCR_WTIF;
+            if (t->wtcr & NPCM7XX_WTCR_WTIE) {
+                /* send interrupt */
+                qemu_irq_raise(t->irq);
+            }
+            npcm7xx_watchdog_timer_reset_cycles(t,
+                    NPCM7XX_WATCHDOG_INTERRUPT_TO_RESET_CYCLES);
+            npcm7xx_timer_start(&t->base_timer);
+        }
+    }
 }
 
 static void npcm7xx_timer_hold_reset(Object *obj)
@@ -467,6 +603,7 @@ static void npcm7xx_timer_hold_reset(Object *obj)
     for (i = 0; i < NPCM7XX_TIMERS_PER_CTRL; i++) {
         qemu_irq_lower(s->timer[i].irq);
     }
+    qemu_irq_lower(s->watchdog_timer.irq);
 }
 
 static void npcm7xx_timer_realize(DeviceState *dev, Error **errp)
@@ -474,43 +611,80 @@ static void npcm7xx_timer_realize(DeviceState *dev, Error **errp)
     NPCM7xxTimerCtrlState *s = NPCM7XX_TIMER(dev);
     SysBusDevice *sbd = &s->parent;
     int i;
+    NPCM7xxWatchdogTimer *w;
 
     for (i = 0; i < NPCM7XX_TIMERS_PER_CTRL; i++) {
         NPCM7xxTimer *t = &s->timer[i];
         t->ctrl = s;
-        timer_init_ns(&t->qtimer, QEMU_CLOCK_VIRTUAL, npcm7xx_timer_expired, t);
+        timer_init_ns(&t->base_timer.qtimer, QEMU_CLOCK_VIRTUAL,
+                npcm7xx_timer_expired, t);
         sysbus_init_irq(sbd, &t->irq);
     }
 
+    w = &s->watchdog_timer;
+    w->ctrl = s;
+    timer_init_ns(&w->base_timer.qtimer, QEMU_CLOCK_VIRTUAL,
+            npcm7xx_watchdog_timer_expired, w);
+    sysbus_init_irq(sbd, &w->irq);
+
     memory_region_init_io(&s->iomem, OBJECT(s), &npcm7xx_timer_ops, s,
                           TYPE_NPCM7XX_TIMER, 4 * KiB);
     sysbus_init_mmio(sbd, &s->iomem);
+    qdev_init_gpio_out_named(dev, &w->reset_signal,
+            NPCM7XX_WATCHDOG_RESET_GPIO_OUT, 1);
 }
 
-static const VMStateDescription vmstate_npcm7xx_timer = {
-    .name = "npcm7xx-timer",
+static const VMStateDescription vmstate_npcm7xx_base_timer = {
+    .name = "npcm7xx-base-timer",
     .version_id = 0,
     .minimum_version_id = 0,
     .fields = (VMStateField[]) {
-        VMSTATE_TIMER(qtimer, NPCM7xxTimer),
-        VMSTATE_INT64(expires_ns, NPCM7xxTimer),
-        VMSTATE_INT64(remaining_ns, NPCM7xxTimer),
+        VMSTATE_TIMER(qtimer, NPCM7xxBaseTimer),
+        VMSTATE_INT64(expires_ns, NPCM7xxBaseTimer),
+        VMSTATE_INT64(remaining_ns, NPCM7xxBaseTimer),
+        VMSTATE_END_OF_LIST(),
+    },
+};
+
+static const VMStateDescription vmstate_npcm7xx_timer = {
+    .name = "npcm7xx-timer",
+    .version_id = 1,
+    .minimum_version_id = 1,
+    .fields = (VMStateField[]) {
+        VMSTATE_STRUCT(base_timer, NPCM7xxTimer,
+                             0, vmstate_npcm7xx_base_timer,
+                             NPCM7xxBaseTimer),
         VMSTATE_UINT32(tcsr, NPCM7xxTimer),
         VMSTATE_UINT32(ticr, NPCM7xxTimer),
         VMSTATE_END_OF_LIST(),
     },
 };
 
-static const VMStateDescription vmstate_npcm7xx_timer_ctrl = {
-    .name = "npcm7xx-timer-ctrl",
+static const VMStateDescription vmstate_npcm7xx_watchdog_timer = {
+    .name = "npcm7xx-watchdog-timer",
     .version_id = 0,
     .minimum_version_id = 0,
     .fields = (VMStateField[]) {
+        VMSTATE_STRUCT(base_timer, NPCM7xxWatchdogTimer,
+                             0, vmstate_npcm7xx_base_timer,
+                             NPCM7xxBaseTimer),
+        VMSTATE_UINT32(wtcr, NPCM7xxWatchdogTimer),
+        VMSTATE_END_OF_LIST(),
+    },
+};
+
+static const VMStateDescription vmstate_npcm7xx_timer_ctrl = {
+    .name = "npcm7xx-timer-ctrl",
+    .version_id = 1,
+    .minimum_version_id = 1,
+    .fields = (VMStateField[]) {
         VMSTATE_UINT32(tisr, NPCM7xxTimerCtrlState),
-        VMSTATE_UINT32(wtcr, NPCM7xxTimerCtrlState),
         VMSTATE_STRUCT_ARRAY(timer, NPCM7xxTimerCtrlState,
                              NPCM7XX_TIMERS_PER_CTRL, 0, vmstate_npcm7xx_timer,
                              NPCM7xxTimer),
+        VMSTATE_STRUCT(watchdog_timer, NPCM7xxTimerCtrlState,
+                             0, vmstate_npcm7xx_watchdog_timer,
+                             NPCM7xxWatchdogTimer),
         VMSTATE_END_OF_LIST(),
     },
 };