hw: rtc: Add Goldfish RTC device

This patch adds model for Google Goldfish virtual platform RTC device.

We will be adding Goldfish RTC device to the QEMU RISC-V virt machine
for providing real date-time to Guest Linux. The corresponding Linux
driver for Goldfish RTC device is already available in upstream Linux.

For now, VM migration support is available but untested for Goldfish RTC
device. It will be hardened in-future when we implement VM migration for
KVM RISC-V.

Signed-off-by: Anup Patel <anup.patel@wdc.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>

hw/rtc/Kconfig

@@ -22,3 +22,6 @@ config MC146818RTC
 
 config SUN4V_RTC
     bool
+
+config GOLDFISH_RTC
+    bool

hw/rtc/Makefile.objs

@@ -11,3 +11,4 @@ common-obj-$(CONFIG_EXYNOS4) += exynos4210_rtc.o
 obj-$(CONFIG_MC146818RTC) += mc146818rtc.o
 common-obj-$(CONFIG_SUN4V_RTC) += sun4v-rtc.o
 common-obj-$(CONFIG_ASPEED_SOC) += aspeed_rtc.o
+common-obj-$(CONFIG_GOLDFISH_RTC) += goldfish_rtc.o

hw/rtc/goldfish_rtc.c

@@ -0,0 +1,285 @@
+/*
+ * Goldfish virtual platform RTC
+ *
+ * Copyright (C) 2019 Western Digital Corporation or its affiliates.
+ *
+ * For more details on Google Goldfish virtual platform refer:
+ * https://android.googlesource.com/platform/external/qemu/+/refs/heads/emu-2.0-release/docs/GOLDFISH-VIRTUAL-HARDWARE.TXT
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2 or later, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope 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-common.h"
+#include "hw/rtc/goldfish_rtc.h"
+#include "migration/vmstate.h"
+#include "hw/irq.h"
+#include "hw/qdev-properties.h"
+#include "hw/sysbus.h"
+#include "qemu/bitops.h"
+#include "qemu/timer.h"
+#include "sysemu/sysemu.h"
+#include "qemu/cutils.h"
+#include "qemu/log.h"
+
+#include "trace.h"
+
+#define RTC_TIME_LOW            0x00
+#define RTC_TIME_HIGH           0x04
+#define RTC_ALARM_LOW           0x08
+#define RTC_ALARM_HIGH          0x0c
+#define RTC_IRQ_ENABLED         0x10
+#define RTC_CLEAR_ALARM         0x14
+#define RTC_ALARM_STATUS        0x18
+#define RTC_CLEAR_INTERRUPT     0x1c
+
+static void goldfish_rtc_update(GoldfishRTCState *s)
+{
+    qemu_set_irq(s->irq, (s->irq_pending & s->irq_enabled) ? 1 : 0);
+}
+
+static void goldfish_rtc_interrupt(void *opaque)
+{
+    GoldfishRTCState *s = (GoldfishRTCState *)opaque;
+
+    s->alarm_running = 0;
+    s->irq_pending = 1;
+    goldfish_rtc_update(s);
+}
+
+static uint64_t goldfish_rtc_get_count(GoldfishRTCState *s)
+{
+    return s->tick_offset + (uint64_t)qemu_clock_get_ns(rtc_clock);
+}
+
+static void goldfish_rtc_clear_alarm(GoldfishRTCState *s)
+{
+    timer_del(s->timer);
+    s->alarm_running = 0;
+}
+
+static void goldfish_rtc_set_alarm(GoldfishRTCState *s)
+{
+    uint64_t ticks = goldfish_rtc_get_count(s);
+    uint64_t event = s->alarm_next;
+
+    if (event <= ticks) {
+        goldfish_rtc_clear_alarm(s);
+        goldfish_rtc_interrupt(s);
+    } else {
+        /*
+         * We should be setting timer expiry to:
+         *     qemu_clock_get_ns(rtc_clock) + (event - ticks)
+         * but this is equivalent to:
+         *     event - s->tick_offset
+         */
+        timer_mod(s->timer, event - s->tick_offset);
+        s->alarm_running = 1;
+    }
+}
+
+static uint64_t goldfish_rtc_read(void *opaque, hwaddr offset,
+                                  unsigned size)
+{
+    GoldfishRTCState *s = opaque;
+    uint64_t r = 0;
+
+    switch (offset) {
+    case RTC_TIME_LOW:
+        r = goldfish_rtc_get_count(s) & 0xffffffff;
+        break;
+    case RTC_TIME_HIGH:
+        r = goldfish_rtc_get_count(s) >> 32;
+        break;
+    case RTC_ALARM_LOW:
+        r = s->alarm_next & 0xffffffff;
+        break;
+    case RTC_ALARM_HIGH:
+        r = s->alarm_next >> 32;
+        break;
+    case RTC_IRQ_ENABLED:
+        r = s->irq_enabled;
+        break;
+    case RTC_ALARM_STATUS:
+        r = s->alarm_running;
+        break;
+    default:
+        qemu_log_mask(LOG_GUEST_ERROR,
+                  "%s: offset 0x%x is UNIMP.\n", __func__, (uint32_t)offset);
+        break;
+    }
+
+    trace_goldfish_rtc_read(offset, r);
+
+    return r;
+}
+
+static void goldfish_rtc_write(void *opaque, hwaddr offset,
+                               uint64_t value, unsigned size)
+{
+    GoldfishRTCState *s = opaque;
+    uint64_t current_tick, new_tick;
+
+    switch (offset) {
+    case RTC_TIME_LOW:
+        current_tick = goldfish_rtc_get_count(s);
+        new_tick = deposit64(current_tick, 0, 32, value);
+        s->tick_offset += new_tick - current_tick;
+        break;
+    case RTC_TIME_HIGH:
+        current_tick = goldfish_rtc_get_count(s);
+        new_tick = deposit64(current_tick, 32, 32, value);
+        s->tick_offset += new_tick - current_tick;
+        break;
+    case RTC_ALARM_LOW:
+        s->alarm_next = deposit64(s->alarm_next, 0, 32, value);
+        goldfish_rtc_set_alarm(s);
+        break;
+    case RTC_ALARM_HIGH:
+        s->alarm_next = deposit64(s->alarm_next, 32, 32, value);
+        break;
+    case RTC_IRQ_ENABLED:
+        s->irq_enabled = (uint32_t)(value & 0x1);
+        goldfish_rtc_update(s);
+        break;
+    case RTC_CLEAR_ALARM:
+        goldfish_rtc_clear_alarm(s);
+        break;
+    case RTC_CLEAR_INTERRUPT:
+        s->irq_pending = 0;
+        goldfish_rtc_update(s);
+        break;
+    default:
+        qemu_log_mask(LOG_GUEST_ERROR,
+                  "%s: offset 0x%x is UNIMP.\n", __func__, (uint32_t)offset);
+        break;
+    }
+
+    trace_goldfish_rtc_write(offset, value);
+}
+
+static int goldfish_rtc_pre_save(void *opaque)
+{
+    uint64_t delta;
+    GoldfishRTCState *s = opaque;
+
+    /*
+     * We want to migrate this offset, which sounds straightforward.
+     * Unfortunately, we cannot directly pass tick_offset because
+     * rtc_clock on destination Host might not be same source Host.
+     *
+     * To tackle, this we pass tick_offset relative to vm_clock from
+     * source Host and make it relative to rtc_clock at destination Host.
+     */
+    delta = qemu_clock_get_ns(rtc_clock) -
+            qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
+    s->tick_offset_vmstate = s->tick_offset + delta;
+
+    return 0;
+}
+
+static int goldfish_rtc_post_load(void *opaque, int version_id)
+{
+    uint64_t delta;
+    GoldfishRTCState *s = opaque;
+
+    /*
+     * We extract tick_offset from tick_offset_vmstate by doing
+     * reverse math compared to pre_save() function.
+     */
+    delta = qemu_clock_get_ns(rtc_clock) -
+            qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
+    s->tick_offset = s->tick_offset_vmstate - delta;
+
+    return 0;
+}
+
+static const MemoryRegionOps goldfish_rtc_ops = {
+    .read = goldfish_rtc_read,
+    .write = goldfish_rtc_write,
+    .endianness = DEVICE_LITTLE_ENDIAN,
+    .valid = {
+        .min_access_size = 4,
+        .max_access_size = 4
+    }
+};
+
+static const VMStateDescription goldfish_rtc_vmstate = {
+    .name = TYPE_GOLDFISH_RTC,
+    .version_id = 1,
+    .pre_save = goldfish_rtc_pre_save,
+    .post_load = goldfish_rtc_post_load,
+    .fields = (VMStateField[]) {
+        VMSTATE_UINT64(tick_offset_vmstate, GoldfishRTCState),
+        VMSTATE_UINT64(alarm_next, GoldfishRTCState),
+        VMSTATE_UINT32(alarm_running, GoldfishRTCState),
+        VMSTATE_UINT32(irq_pending, GoldfishRTCState),
+        VMSTATE_UINT32(irq_enabled, GoldfishRTCState),
+        VMSTATE_END_OF_LIST()
+    }
+};
+
+static void goldfish_rtc_reset(DeviceState *dev)
+{
+    GoldfishRTCState *s = GOLDFISH_RTC(dev);
+    struct tm tm;
+
+    timer_del(s->timer);
+
+    qemu_get_timedate(&tm, 0);
+    s->tick_offset = mktimegm(&tm);
+    s->tick_offset *= NANOSECONDS_PER_SECOND;
+    s->tick_offset -= qemu_clock_get_ns(rtc_clock);
+    s->tick_offset_vmstate = 0;
+    s->alarm_next = 0;
+    s->alarm_running = 0;
+    s->irq_pending = 0;
+    s->irq_enabled = 0;
+}
+
+static void goldfish_rtc_realize(DeviceState *d, Error **errp)
+{
+    SysBusDevice *dev = SYS_BUS_DEVICE(d);
+    GoldfishRTCState *s = GOLDFISH_RTC(d);
+
+    memory_region_init_io(&s->iomem, OBJECT(s), &goldfish_rtc_ops, s,
+                          "goldfish_rtc", 0x24);
+    sysbus_init_mmio(dev, &s->iomem);
+
+    sysbus_init_irq(dev, &s->irq);
+
+    s->timer = timer_new_ns(rtc_clock, goldfish_rtc_interrupt, s);
+}
+
+static void goldfish_rtc_class_init(ObjectClass *klass, void *data)
+{
+    DeviceClass *dc = DEVICE_CLASS(klass);
+
+    dc->realize = goldfish_rtc_realize;
+    dc->reset = goldfish_rtc_reset;
+    dc->vmsd = &goldfish_rtc_vmstate;
+}
+
+static const TypeInfo goldfish_rtc_info = {
+    .name          = TYPE_GOLDFISH_RTC,
+    .parent        = TYPE_SYS_BUS_DEVICE,
+    .instance_size = sizeof(GoldfishRTCState),
+    .class_init    = goldfish_rtc_class_init,
+};
+
+static void goldfish_rtc_register_types(void)
+{
+    type_register_static(&goldfish_rtc_info);
+}
+
+type_init(goldfish_rtc_register_types)

hw/rtc/trace-events

@@ -23,3 +23,7 @@ m48txx_nvram_io_read(uint64_t addr, uint64_t value) "io read addr:0x%04" PRIx64
 m48txx_nvram_io_write(uint64_t addr, uint64_t value) "io write addr:0x%04" PRIx64 " value:0x%02" PRIx64
 m48txx_nvram_mem_read(uint32_t addr, uint32_t value) "mem read addr:0x%04x value:0x%02x"
 m48txx_nvram_mem_write(uint32_t addr, uint32_t value) "mem write addr:0x%04x value:0x%02x"
+
+# goldfish_rtc.c
+goldfish_rtc_read(uint64_t addr, uint64_t value) "addr 0x%02" PRIx64 " value 0x%08" PRIx64
+goldfish_rtc_write(uint64_t addr, uint64_t value) "addr 0x%02" PRIx64 " value 0x%08" PRIx64

include/hw/rtc/goldfish_rtc.h

@@ -0,0 +1,46 @@
+/*
+ * Goldfish virtual platform RTC
+ *
+ * Copyright (C) 2019 Western Digital Corporation or its affiliates.
+ *
+ * For more details on Google Goldfish virtual platform refer:
+ * https://android.googlesource.com/platform/external/qemu/+/master/docs/GOLDFISH-VIRTUAL-HARDWARE.TXT
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2 or later, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope 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/>.
+ */
+
+#ifndef HW_RTC_GOLDFISH_RTC_H
+#define HW_RTC_GOLDFISH_RTC_H
+
+#include "hw/sysbus.h"
+
+#define TYPE_GOLDFISH_RTC "goldfish_rtc"
+#define GOLDFISH_RTC(obj) \
+    OBJECT_CHECK(GoldfishRTCState, (obj), TYPE_GOLDFISH_RTC)
+
+typedef struct GoldfishRTCState {
+    SysBusDevice parent_obj;
+
+    MemoryRegion iomem;
+    QEMUTimer *timer;
+    qemu_irq irq;
+
+    uint64_t tick_offset;
+    uint64_t tick_offset_vmstate;
+    uint64_t alarm_next;
+    uint32_t alarm_running;
+    uint32_t irq_pending;
+    uint32_t irq_enabled;
+} GoldfishRTCState;
+
+#endif