hw/watchdog: Allwinner WDT emulation for system reset

This patch adds basic support for Allwinner WDT.
Both sun4i and sun6i variants are supported.
However, interrupt generation is not supported, so WDT can be used only to trigger system reset.

Signed-off-by: Strahinja Jankovic <strahinja.p.jankovic@gmail.com>
Reviewed-by: Niek Linnenbank <nieklinnenbank@gmail.com>
Tested-by: Niek Linnenbank <nieklinnenbank@gmail.com>
Message-id: 20230326202256.22980-2-strahinja.p.jankovic@gmail.com
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

4 files changed, 428 insertions, 0 deletions

diff --git a/hw/watchdog/Kconfig b/hw/watchdog/Kconfig
index 66e1d02..861fd00 100644
--- a/hw/watchdog/Kconfig
+++ b/hw/watchdog/Kconfig
@@ -20,3 +20,7 @@ config WDT_IMX2
 
 config WDT_SBSA
     bool
+
+config ALLWINNER_WDT
+    bool
+    select PTIMER
diff --git a/hw/watchdog/allwinner-wdt.c b/hw/watchdog/allwinner-wdt.c
new file mode 100644
index 0000000..6205765
--- /dev/null
+++ b/hw/watchdog/allwinner-wdt.c
@@ -0,0 +1,416 @@
+/*
+ * Allwinner Watchdog emulation
+ *
+ * Copyright (C) 2023 Strahinja Jankovic <strahinja.p.jankovic@gmail.com>
+ *
+ *  This file is derived from Allwinner RTC,
+ *  by Niek Linnenbank.
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "qemu/osdep.h"
+#include "qemu/log.h"
+#include "qemu/units.h"
+#include "qemu/module.h"
+#include "trace.h"
+#include "hw/sysbus.h"
+#include "hw/registerfields.h"
+#include "hw/watchdog/allwinner-wdt.h"
+#include "sysemu/watchdog.h"
+#include "migration/vmstate.h"
+
+/* WDT registers */
+enum {
+    REG_IRQ_EN = 0,     /* Watchdog interrupt enable */
+    REG_IRQ_STA,        /* Watchdog interrupt status */
+    REG_CTRL,           /* Watchdog control register */
+    REG_CFG,            /* Watchdog configuration register */
+    REG_MODE,           /* Watchdog mode register */
+};
+
+/* Universal WDT register flags */
+#define WDT_RESTART_MASK    (1 << 0)
+#define WDT_EN_MASK         (1 << 0)
+
+/* sun4i specific WDT register flags */
+#define RST_EN_SUN4I_MASK       (1 << 1)
+#define INTV_VALUE_SUN4I_SHIFT  (3)
+#define INTV_VALUE_SUN4I_MASK   (0xfu << INTV_VALUE_SUN4I_SHIFT)
+
+/* sun6i specific WDT register flags */
+#define RST_EN_SUN6I_MASK       (1 << 0)
+#define KEY_FIELD_SUN6I_SHIFT   (1)
+#define KEY_FIELD_SUN6I_MASK    (0xfffu << KEY_FIELD_SUN6I_SHIFT)
+#define KEY_FIELD_SUN6I         (0xA57u)
+#define INTV_VALUE_SUN6I_SHIFT  (4)
+#define INTV_VALUE_SUN6I_MASK   (0xfu << INTV_VALUE_SUN6I_SHIFT)
+
+/* Map of INTV_VALUE to 0.5s units. */
+static const uint8_t allwinner_wdt_count_map[] = {
+    1,
+    2,
+    4,
+    6,
+    8,
+    10,
+    12,
+    16,
+    20,
+    24,
+    28,
+    32
+};
+
+/* WDT sun4i register map (offset to name) */
+const uint8_t allwinner_wdt_sun4i_regmap[] = {
+    [0x0000] = REG_CTRL,
+    [0x0004] = REG_MODE,
+};
+
+/* WDT sun6i register map (offset to name) */
+const uint8_t allwinner_wdt_sun6i_regmap[] = {
+    [0x0000] = REG_IRQ_EN,
+    [0x0004] = REG_IRQ_STA,
+    [0x0010] = REG_CTRL,
+    [0x0014] = REG_CFG,
+    [0x0018] = REG_MODE,
+};
+
+static bool allwinner_wdt_sun4i_read(AwWdtState *s, uint32_t offset)
+{
+    /* no sun4i specific registers currently implemented */
+    return false;
+}
+
+static bool allwinner_wdt_sun4i_write(AwWdtState *s, uint32_t offset,
+                                      uint32_t data)
+{
+    /* no sun4i specific registers currently implemented */
+    return false;
+}
+
+static bool allwinner_wdt_sun4i_can_reset_system(AwWdtState *s)
+{
+    if (s->regs[REG_MODE] & RST_EN_SUN4I_MASK) {
+        return true;
+    } else {
+        return false;
+    }
+}
+
+static bool allwinner_wdt_sun4i_is_key_valid(AwWdtState *s, uint32_t val)
+{
+    /* sun4i has no key */
+    return true;
+}
+
+static uint8_t allwinner_wdt_sun4i_get_intv_value(AwWdtState *s)
+{
+    return ((s->regs[REG_MODE] & INTV_VALUE_SUN4I_MASK) >>
+            INTV_VALUE_SUN4I_SHIFT);
+}
+
+static bool allwinner_wdt_sun6i_read(AwWdtState *s, uint32_t offset)
+{
+    const AwWdtClass *c = AW_WDT_GET_CLASS(s);
+
+    switch (c->regmap[offset]) {
+    case REG_IRQ_EN:
+    case REG_IRQ_STA:
+    case REG_CFG:
+        return true;
+    default:
+        break;
+    }
+    return false;
+}
+
+static bool allwinner_wdt_sun6i_write(AwWdtState *s, uint32_t offset,
+                                      uint32_t data)
+{
+    const AwWdtClass *c = AW_WDT_GET_CLASS(s);
+
+    switch (c->regmap[offset]) {
+    case REG_IRQ_EN:
+    case REG_IRQ_STA:
+    case REG_CFG:
+        return true;
+    default:
+        break;
+    }
+    return false;
+}
+
+static bool allwinner_wdt_sun6i_can_reset_system(AwWdtState *s)
+{
+    if (s->regs[REG_CFG] & RST_EN_SUN6I_MASK) {
+        return true;
+    } else {
+        return false;
+    }
+}
+
+static bool allwinner_wdt_sun6i_is_key_valid(AwWdtState *s, uint32_t val)
+{
+    uint16_t key = (val & KEY_FIELD_SUN6I_MASK) >> KEY_FIELD_SUN6I_SHIFT;
+    return (key == KEY_FIELD_SUN6I);
+}
+
+static uint8_t allwinner_wdt_sun6i_get_intv_value(AwWdtState *s)
+{
+    return ((s->regs[REG_MODE] & INTV_VALUE_SUN6I_MASK) >>
+            INTV_VALUE_SUN6I_SHIFT);
+}
+
+static void allwinner_wdt_update_timer(AwWdtState *s)
+{
+    const AwWdtClass *c = AW_WDT_GET_CLASS(s);
+    uint8_t count = c->get_intv_value(s);
+
+    ptimer_transaction_begin(s->timer);
+    ptimer_stop(s->timer);
+
+    /* Use map to convert. */
+    if (count < sizeof(allwinner_wdt_count_map)) {
+        ptimer_set_count(s->timer, allwinner_wdt_count_map[count]);
+    } else {
+        qemu_log_mask(LOG_GUEST_ERROR, "%s: incorrect INTV_VALUE 0x%02x\n",
+                __func__, count);
+    }
+
+    ptimer_run(s->timer, 1);
+    ptimer_transaction_commit(s->timer);
+
+    trace_allwinner_wdt_update_timer(count);
+}
+
+static uint64_t allwinner_wdt_read(void *opaque, hwaddr offset,
+                                       unsigned size)
+{
+    AwWdtState *s = AW_WDT(opaque);
+    const AwWdtClass *c = AW_WDT_GET_CLASS(s);
+    uint64_t r;
+
+    if (offset >= c->regmap_size) {
+        qemu_log_mask(LOG_GUEST_ERROR, "%s: out-of-bounds offset 0x%04x\n",
+                      __func__, (uint32_t)offset);
+        return 0;
+    }
+
+    switch (c->regmap[offset]) {
+    case REG_CTRL:
+    case REG_MODE:
+        r = s->regs[c->regmap[offset]];
+        break;
+    default:
+        if (!c->read(s, offset)) {
+            qemu_log_mask(LOG_UNIMP, "%s: unimplemented register 0x%04x\n",
+                            __func__, (uint32_t)offset);
+            return 0;
+        }
+        r = s->regs[c->regmap[offset]];
+        break;
+    }
+
+    trace_allwinner_wdt_read(offset, r, size);
+
+    return r;
+}
+
+static void allwinner_wdt_write(void *opaque, hwaddr offset,
+                                   uint64_t val, unsigned size)
+{
+    AwWdtState *s = AW_WDT(opaque);
+    const AwWdtClass *c = AW_WDT_GET_CLASS(s);
+    uint32_t old_val;
+
+    if (offset >= c->regmap_size) {
+        qemu_log_mask(LOG_GUEST_ERROR, "%s: out-of-bounds offset 0x%04x\n",
+                      __func__, (uint32_t)offset);
+        return;
+    }
+
+   trace_allwinner_wdt_write(offset, val, size);
+
+    switch (c->regmap[offset]) {
+    case REG_CTRL:
+        if (c->is_key_valid(s, val)) {
+            if (val & WDT_RESTART_MASK) {
+                /* Kick timer */
+                allwinner_wdt_update_timer(s);
+            }
+        }
+        break;
+    case REG_MODE:
+        old_val = s->regs[REG_MODE];
+        s->regs[REG_MODE] = (uint32_t)val;
+
+        /* Check for rising edge on WDOG_MODE_EN */
+        if ((s->regs[REG_MODE] & ~old_val) & WDT_EN_MASK) {
+            allwinner_wdt_update_timer(s);
+        }
+        break;
+    default:
+        if (!c->write(s, offset, val)) {
+            qemu_log_mask(LOG_UNIMP, "%s: unimplemented register 0x%04x\n",
+                          __func__, (uint32_t)offset);
+        }
+        s->regs[c->regmap[offset]] = (uint32_t)val;
+        break;
+    }
+}
+
+static const MemoryRegionOps allwinner_wdt_ops = {
+    .read = allwinner_wdt_read,
+    .write = allwinner_wdt_write,
+    .endianness = DEVICE_NATIVE_ENDIAN,
+    .valid = {
+        .min_access_size = 4,
+        .max_access_size = 4,
+    },
+    .impl.min_access_size = 4,
+};
+
+static void allwinner_wdt_expired(void *opaque)
+{
+    AwWdtState *s = AW_WDT(opaque);
+    const AwWdtClass *c = AW_WDT_GET_CLASS(s);
+
+    bool enabled = s->regs[REG_MODE] & WDT_EN_MASK;
+    bool reset_enabled = c->can_reset_system(s);
+
+    trace_allwinner_wdt_expired(enabled, reset_enabled);
+
+    /* Perform watchdog action if watchdog is enabled and can trigger reset */
+    if (enabled && reset_enabled) {
+        watchdog_perform_action();
+    }
+}
+
+static void allwinner_wdt_reset_enter(Object *obj, ResetType type)
+{
+    AwWdtState *s = AW_WDT(obj);
+
+    trace_allwinner_wdt_reset_enter();
+
+    /* Clear registers */
+    memset(s->regs, 0, sizeof(s->regs));
+}
+
+static const VMStateDescription allwinner_wdt_vmstate = {
+    .name = "allwinner-wdt",
+    .version_id = 1,
+    .minimum_version_id = 1,
+    .fields = (VMStateField[]) {
+        VMSTATE_PTIMER(timer, AwWdtState),
+        VMSTATE_UINT32_ARRAY(regs, AwWdtState, AW_WDT_REGS_NUM),
+        VMSTATE_END_OF_LIST()
+    }
+};
+
+static void allwinner_wdt_init(Object *obj)
+{
+    SysBusDevice *sbd = SYS_BUS_DEVICE(obj);
+    AwWdtState *s = AW_WDT(obj);
+    const AwWdtClass *c = AW_WDT_GET_CLASS(s);
+
+    /* Memory mapping */
+    memory_region_init_io(&s->iomem, OBJECT(s), &allwinner_wdt_ops, s,
+                          TYPE_AW_WDT, c->regmap_size * 4);
+    sysbus_init_mmio(sbd, &s->iomem);
+}
+
+static void allwinner_wdt_realize(DeviceState *dev, Error **errp)
+{
+    AwWdtState *s = AW_WDT(dev);
+
+    s->timer = ptimer_init(allwinner_wdt_expired, s,
+                           PTIMER_POLICY_NO_IMMEDIATE_TRIGGER |
+                           PTIMER_POLICY_NO_IMMEDIATE_RELOAD |
+                           PTIMER_POLICY_NO_COUNTER_ROUND_DOWN);
+
+    ptimer_transaction_begin(s->timer);
+    /* Set to 2Hz (0.5s period); other periods are multiples of 0.5s. */
+    ptimer_set_freq(s->timer, 2);
+    ptimer_set_limit(s->timer, 0xff, 1);
+    ptimer_transaction_commit(s->timer);
+}
+
+static void allwinner_wdt_class_init(ObjectClass *klass, void *data)
+{
+    DeviceClass *dc = DEVICE_CLASS(klass);
+    ResettableClass *rc = RESETTABLE_CLASS(klass);
+
+    rc->phases.enter = allwinner_wdt_reset_enter;
+    dc->realize = allwinner_wdt_realize;
+    dc->vmsd = &allwinner_wdt_vmstate;
+}
+
+static void allwinner_wdt_sun4i_class_init(ObjectClass *klass, void *data)
+{
+    AwWdtClass *awc = AW_WDT_CLASS(klass);
+
+    awc->regmap = allwinner_wdt_sun4i_regmap;
+    awc->regmap_size = sizeof(allwinner_wdt_sun4i_regmap);
+    awc->read = allwinner_wdt_sun4i_read;
+    awc->write = allwinner_wdt_sun4i_write;
+    awc->can_reset_system = allwinner_wdt_sun4i_can_reset_system;
+    awc->is_key_valid = allwinner_wdt_sun4i_is_key_valid;
+    awc->get_intv_value = allwinner_wdt_sun4i_get_intv_value;
+}
+
+static void allwinner_wdt_sun6i_class_init(ObjectClass *klass, void *data)
+{
+    AwWdtClass *awc = AW_WDT_CLASS(klass);
+
+    awc->regmap = allwinner_wdt_sun6i_regmap;
+    awc->regmap_size = sizeof(allwinner_wdt_sun6i_regmap);
+    awc->read = allwinner_wdt_sun6i_read;
+    awc->write = allwinner_wdt_sun6i_write;
+    awc->can_reset_system = allwinner_wdt_sun6i_can_reset_system;
+    awc->is_key_valid = allwinner_wdt_sun6i_is_key_valid;
+    awc->get_intv_value = allwinner_wdt_sun6i_get_intv_value;
+}
+
+static const TypeInfo allwinner_wdt_info = {
+    .name          = TYPE_AW_WDT,
+    .parent        = TYPE_SYS_BUS_DEVICE,
+    .instance_init = allwinner_wdt_init,
+    .instance_size = sizeof(AwWdtState),
+    .class_init    = allwinner_wdt_class_init,
+    .class_size    = sizeof(AwWdtClass),
+    .abstract      = true,
+};
+
+static const TypeInfo allwinner_wdt_sun4i_info = {
+    .name          = TYPE_AW_WDT_SUN4I,
+    .parent        = TYPE_AW_WDT,
+    .class_init    = allwinner_wdt_sun4i_class_init,
+};
+
+static const TypeInfo allwinner_wdt_sun6i_info = {
+    .name          = TYPE_AW_WDT_SUN6I,
+    .parent        = TYPE_AW_WDT,
+    .class_init    = allwinner_wdt_sun6i_class_init,
+};
+
+static void allwinner_wdt_register(void)
+{
+    type_register_static(&allwinner_wdt_info);
+    type_register_static(&allwinner_wdt_sun4i_info);
+    type_register_static(&allwinner_wdt_sun6i_info);
+}
+
+type_init(allwinner_wdt_register)
diff --git a/hw/watchdog/meson.build b/hw/watchdog/meson.build
index 8974b5c..5dcd4fb 100644
--- a/hw/watchdog/meson.build
+++ b/hw/watchdog/meson.build
@@ -1,4 +1,5 @@
 softmmu_ss.add(files('watchdog.c'))
+softmmu_ss.add(when: 'CONFIG_ALLWINNER_WDT', if_true: files('allwinner-wdt.c'))
 softmmu_ss.add(when: 'CONFIG_CMSDK_APB_WATCHDOG', if_true: files('cmsdk-apb-watchdog.c'))
 softmmu_ss.add(when: 'CONFIG_WDT_IB6300ESB', if_true: files('wdt_i6300esb.c'))
 softmmu_ss.add(when: 'CONFIG_WDT_IB700', if_true: files('wdt_ib700.c'))
diff --git a/hw/watchdog/trace-events b/hw/watchdog/trace-events
index 54371ae..2739570 100644
--- a/hw/watchdog/trace-events
+++ b/hw/watchdog/trace-events
@@ -1,5 +1,12 @@
 # See docs/devel/tracing.rst for syntax documentation.
 
+# allwinner-wdt.c
+allwinner_wdt_read(uint64_t offset, uint64_t data, unsigned size) "Allwinner watchdog read: offset 0x%" PRIx64 " data 0x%" PRIx64 " size %u"
+allwinner_wdt_write(uint64_t offset, uint64_t data, unsigned size) "Allwinner watchdog write: offset 0x%" PRIx64 " data 0x%" PRIx64 " size %u"
+allwinner_wdt_reset_enter(void) "Allwinner watchdog: reset"
+allwinner_wdt_update_timer(uint8_t count) "Allwinner watchdog: count %" PRIu8
+allwinner_wdt_expired(bool enabled, bool reset_enabled) "Allwinner watchdog: enabled %u reset_enabled %u"
+
 # cmsdk-apb-watchdog.c
 cmsdk_apb_watchdog_read(uint64_t offset, uint64_t data, unsigned size) "CMSDK APB watchdog read: offset 0x%" PRIx64 " data 0x%" PRIx64 " size %u"
 cmsdk_apb_watchdog_write(uint64_t offset, uint64_t data, unsigned size) "CMSDK APB watchdog write: offset 0x%" PRIx64 " data 0x%" PRIx64 " size %u"