hw/timer: Initial commit of Ibex Timer

Add support for the Ibex timer. This is used with the RISC-V
mtime/mtimecmp similar to the SiFive CLINT.

We currently don't support changing the prescale or the timervalue.

Signed-off-by: Alistair Francis <alistair.francis@wdc.com>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Message-id: 716fdea2244515ce86a2c46fe69467d013c03147.1624001156.git.alistair.francis@wdc.com

2 files changed, 306 insertions, 0 deletions

diff --git a/hw/timer/ibex_timer.c b/hw/timer/ibex_timer.c
new file mode 100644
index 0000000..5befb53
--- /dev/null
+++ b/hw/timer/ibex_timer.c
@@ -0,0 +1,305 @@
+/*
+ * QEMU lowRISC Ibex Timer device
+ *
+ * Copyright (c) 2021 Western Digital
+ *
+ * For details check the documentation here:
+ *    https://docs.opentitan.org/hw/ip/rv_timer/doc/
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+#include "qemu/osdep.h"
+#include "qemu/log.h"
+#include "qemu/timer.h"
+#include "hw/timer/ibex_timer.h"
+#include "hw/irq.h"
+#include "hw/qdev-properties.h"
+#include "target/riscv/cpu.h"
+#include "migration/vmstate.h"
+
+REG32(CTRL, 0x00)
+    FIELD(CTRL, ACTIVE, 0, 1)
+REG32(CFG0, 0x100)
+    FIELD(CFG0, PRESCALE, 0, 12)
+    FIELD(CFG0, STEP, 16, 8)
+REG32(LOWER0, 0x104)
+REG32(UPPER0, 0x108)
+REG32(COMPARE_LOWER0, 0x10C)
+REG32(COMPARE_UPPER0, 0x110)
+REG32(INTR_ENABLE, 0x114)
+    FIELD(INTR_ENABLE, IE_0, 0, 1)
+REG32(INTR_STATE, 0x118)
+    FIELD(INTR_STATE, IS_0, 0, 1)
+REG32(INTR_TEST, 0x11C)
+    FIELD(INTR_TEST, T_0, 0, 1)
+
+static uint64_t cpu_riscv_read_rtc(uint32_t timebase_freq)
+{
+    return muldiv64(qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL),
+                    timebase_freq, NANOSECONDS_PER_SECOND);
+}
+
+static void ibex_timer_update_irqs(IbexTimerState *s)
+{
+    CPUState *cs = qemu_get_cpu(0);
+    RISCVCPU *cpu = RISCV_CPU(cs);
+    uint64_t value = s->timer_compare_lower0 |
+                         ((uint64_t)s->timer_compare_upper0 << 32);
+    uint64_t next, diff;
+    uint64_t now = cpu_riscv_read_rtc(s->timebase_freq);
+
+    if (!(s->timer_ctrl & R_CTRL_ACTIVE_MASK)) {
+        /* Timer isn't active */
+        return;
+    }
+
+    /* Update the CPUs mtimecmp */
+    cpu->env.timecmp = value;
+
+    if (cpu->env.timecmp <= now) {
+        /*
+         * If the mtimecmp was in the past raise the interrupt now.
+         */
+        riscv_cpu_update_mip(cpu, MIP_MTIP, BOOL_TO_MASK(1));
+        if (s->timer_intr_enable & R_INTR_ENABLE_IE_0_MASK) {
+            s->timer_intr_state |= R_INTR_STATE_IS_0_MASK;
+            qemu_set_irq(s->irq, true);
+        }
+        return;
+    }
+
+    /* Setup a timer to trigger the interrupt in the future */
+    riscv_cpu_update_mip(cpu, MIP_MTIP, BOOL_TO_MASK(0));
+    qemu_set_irq(s->irq, false);
+
+    diff = cpu->env.timecmp - now;
+    next = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) +
+                                 muldiv64(diff,
+                                          NANOSECONDS_PER_SECOND,
+                                          s->timebase_freq);
+
+    if (next < qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL)) {
+        /* We overflowed the timer, just set it as large as we can */
+        timer_mod(cpu->env.timer, 0x7FFFFFFFFFFFFFFF);
+    } else {
+        timer_mod(cpu->env.timer, next);
+    }
+}
+
+static void ibex_timer_cb(void *opaque)
+{
+    IbexTimerState *s = opaque;
+    CPUState *cs = qemu_get_cpu(0);
+    RISCVCPU *cpu = RISCV_CPU(cs);
+
+    riscv_cpu_update_mip(cpu, MIP_MTIP, BOOL_TO_MASK(1));
+    if (s->timer_intr_enable & R_INTR_ENABLE_IE_0_MASK) {
+        s->timer_intr_state |= R_INTR_STATE_IS_0_MASK;
+        qemu_set_irq(s->irq, true);
+    }
+}
+
+static void ibex_timer_reset(DeviceState *dev)
+{
+    IbexTimerState *s = IBEX_TIMER(dev);
+
+    CPUState *cpu = qemu_get_cpu(0);
+    CPURISCVState *env = cpu->env_ptr;
+    env->timer = timer_new_ns(QEMU_CLOCK_VIRTUAL,
+                              &ibex_timer_cb, s);
+    env->timecmp = 0;
+
+    s->timer_ctrl = 0x00000000;
+    s->timer_cfg0 = 0x00010000;
+    s->timer_compare_lower0 = 0xFFFFFFFF;
+    s->timer_compare_upper0 = 0xFFFFFFFF;
+    s->timer_intr_enable = 0x00000000;
+    s->timer_intr_state = 0x00000000;
+    s->timer_intr_test = 0x00000000;
+
+    ibex_timer_update_irqs(s);
+}
+
+static uint64_t ibex_timer_read(void *opaque, hwaddr addr,
+                                       unsigned int size)
+{
+    IbexTimerState *s = opaque;
+    uint64_t now = cpu_riscv_read_rtc(s->timebase_freq);
+    uint64_t retvalue = 0;
+
+    switch (addr >> 2) {
+    case R_CTRL:
+        retvalue = s->timer_ctrl;
+        break;
+    case R_CFG0:
+        retvalue = s->timer_cfg0;
+        break;
+    case R_LOWER0:
+        retvalue = now;
+        break;
+    case R_UPPER0:
+        retvalue = now >> 32;
+        break;
+    case R_COMPARE_LOWER0:
+        retvalue = s->timer_compare_lower0;
+        break;
+    case R_COMPARE_UPPER0:
+        retvalue = s->timer_compare_upper0;
+        break;
+    case R_INTR_ENABLE:
+        retvalue = s->timer_intr_enable;
+        break;
+    case R_INTR_STATE:
+        retvalue = s->timer_intr_state;
+        break;
+    case R_INTR_TEST:
+        retvalue = s->timer_intr_test;
+        break;
+    default:
+        qemu_log_mask(LOG_GUEST_ERROR,
+                      "%s: Bad offset 0x%"HWADDR_PRIx"\n", __func__, addr);
+        return 0;
+    }
+
+    return retvalue;
+}
+
+static void ibex_timer_write(void *opaque, hwaddr addr,
+                             uint64_t val64, unsigned int size)
+{
+    IbexTimerState *s = opaque;
+    uint32_t val = val64;
+
+    switch (addr >> 2) {
+    case R_CTRL:
+        s->timer_ctrl = val;
+        break;
+    case R_CFG0:
+        qemu_log_mask(LOG_UNIMP, "Changing prescale or step not supported");
+        s->timer_cfg0 = val;
+        break;
+    case R_LOWER0:
+        qemu_log_mask(LOG_UNIMP, "Changing timer value is not supported");
+        break;
+    case R_UPPER0:
+        qemu_log_mask(LOG_UNIMP, "Changing timer value is not supported");
+        break;
+    case R_COMPARE_LOWER0:
+        s->timer_compare_lower0 = val;
+        ibex_timer_update_irqs(s);
+        break;
+    case R_COMPARE_UPPER0:
+        s->timer_compare_upper0 = val;
+        ibex_timer_update_irqs(s);
+        break;
+    case R_INTR_ENABLE:
+        s->timer_intr_enable = val;
+        break;
+    case R_INTR_STATE:
+        /* Write 1 to clear */
+        s->timer_intr_state &= ~val;
+        break;
+    case R_INTR_TEST:
+        s->timer_intr_test = val;
+        if (s->timer_intr_enable &
+            s->timer_intr_test &
+            R_INTR_ENABLE_IE_0_MASK) {
+            s->timer_intr_state |= R_INTR_STATE_IS_0_MASK;
+            qemu_set_irq(s->irq, true);
+        }
+        break;
+    default:
+        qemu_log_mask(LOG_GUEST_ERROR,
+                      "%s: Bad offset 0x%"HWADDR_PRIx"\n", __func__, addr);
+    }
+}
+
+static const MemoryRegionOps ibex_timer_ops = {
+    .read = ibex_timer_read,
+    .write = ibex_timer_write,
+    .endianness = DEVICE_NATIVE_ENDIAN,
+    .impl.min_access_size = 4,
+    .impl.max_access_size = 4,
+};
+
+static int ibex_timer_post_load(void *opaque, int version_id)
+{
+    IbexTimerState *s = opaque;
+
+    ibex_timer_update_irqs(s);
+    return 0;
+}
+
+static const VMStateDescription vmstate_ibex_timer = {
+    .name = TYPE_IBEX_TIMER,
+    .version_id = 1,
+    .minimum_version_id = 1,
+    .post_load = ibex_timer_post_load,
+    .fields = (VMStateField[]) {
+        VMSTATE_UINT32(timer_ctrl, IbexTimerState),
+        VMSTATE_UINT32(timer_cfg0, IbexTimerState),
+        VMSTATE_UINT32(timer_compare_lower0, IbexTimerState),
+        VMSTATE_UINT32(timer_compare_upper0, IbexTimerState),
+        VMSTATE_UINT32(timer_intr_enable, IbexTimerState),
+        VMSTATE_UINT32(timer_intr_state, IbexTimerState),
+        VMSTATE_UINT32(timer_intr_test, IbexTimerState),
+        VMSTATE_END_OF_LIST()
+    }
+};
+
+static Property ibex_timer_properties[] = {
+    DEFINE_PROP_UINT32("timebase-freq", IbexTimerState, timebase_freq, 10000),
+    DEFINE_PROP_END_OF_LIST(),
+};
+
+static void ibex_timer_init(Object *obj)
+{
+    IbexTimerState *s = IBEX_TIMER(obj);
+
+    sysbus_init_irq(SYS_BUS_DEVICE(obj), &s->irq);
+
+    memory_region_init_io(&s->mmio, obj, &ibex_timer_ops, s,
+                          TYPE_IBEX_TIMER, 0x400);
+    sysbus_init_mmio(SYS_BUS_DEVICE(obj), &s->mmio);
+}
+
+static void ibex_timer_class_init(ObjectClass *klass, void *data)
+{
+    DeviceClass *dc = DEVICE_CLASS(klass);
+
+    dc->reset = ibex_timer_reset;
+    dc->vmsd = &vmstate_ibex_timer;
+    device_class_set_props(dc, ibex_timer_properties);
+}
+
+static const TypeInfo ibex_timer_info = {
+    .name          = TYPE_IBEX_TIMER,
+    .parent        = TYPE_SYS_BUS_DEVICE,
+    .instance_size = sizeof(IbexTimerState),
+    .instance_init = ibex_timer_init,
+    .class_init    = ibex_timer_class_init,
+};
+
+static void ibex_timer_register_types(void)
+{
+    type_register_static(&ibex_timer_info);
+}
+
+type_init(ibex_timer_register_types)
diff --git a/hw/timer/meson.build b/hw/timer/meson.build
index 157f540..1aa3cd2 100644
--- a/hw/timer/meson.build
+++ b/hw/timer/meson.build
@@ -33,5 +33,6 @@ softmmu_ss.add(when: 'CONFIG_SSE_COUNTER', if_true: files('sse-counter.c'))
 softmmu_ss.add(when: 'CONFIG_SSE_TIMER', if_true: files('sse-timer.c'))
 softmmu_ss.add(when: 'CONFIG_STM32F2XX_TIMER', if_true: files('stm32f2xx_timer.c'))
 softmmu_ss.add(when: 'CONFIG_XILINX', if_true: files('xilinx_timer.c'))
+specific_ss.add(when: 'CONFIG_IBEX', if_true: files('ibex_timer.c'))
 
 specific_ss.add(when: 'CONFIG_AVR_TIMER16', if_true: files('avr_timer16.c'))