hw/timer: Add NPCM7xx Timer device model

The NPCM730 and NPCM750 SoCs have three timer modules each holding five
timers and some shared registers (e.g. interrupt status).

Each timer runs at 25 MHz divided by a prescaler, and counts down from a
configurable initial value to zero. When zero is reached, the interrupt
flag for the timer is set, and the timer is disabled (one-shot mode) or
reloaded from its initial value (periodic mode).

This implementation is sufficient to boot a Linux kernel configured for
NPCM750. Note that the kernel does not seem to actually turn on the
interrupts.

Reviewed-by: Tyrone Ting <kfting@nuvoton.com>
Reviewed-by: Joel Stanley <joel@jms.id.au>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Tested-by: Alexander Bulekov <alxndr@bu.edu>
Tested-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: Havard Skinnemoen <hskinnemoen@google.com>
Message-id: 20200911052101.2602693-4-hskinnemoen@google.com
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

1 files changed, 543 insertions, 0 deletions

diff --git a/hw/timer/npcm7xx_timer.c b/hw/timer/npcm7xx_timer.c
new file mode 100644
index 0000000..5703e43
--- /dev/null
+++ b/hw/timer/npcm7xx_timer.c
@@ -0,0 +1,543 @@
+/*
+ * Nuvoton NPCM7xx Timer Controller
+ *
+ * Copyright 2020 Google LLC
+ *
+ * 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.
+ */
+
+#include "qemu/osdep.h"
+
+#include "hw/irq.h"
+#include "hw/misc/npcm7xx_clk.h"
+#include "hw/timer/npcm7xx_timer.h"
+#include "migration/vmstate.h"
+#include "qemu/bitops.h"
+#include "qemu/error-report.h"
+#include "qemu/log.h"
+#include "qemu/module.h"
+#include "qemu/timer.h"
+#include "qemu/units.h"
+#include "trace.h"
+
+/* 32-bit register indices. */
+enum NPCM7xxTimerRegisters {
+    NPCM7XX_TIMER_TCSR0,
+    NPCM7XX_TIMER_TCSR1,
+    NPCM7XX_TIMER_TICR0,
+    NPCM7XX_TIMER_TICR1,
+    NPCM7XX_TIMER_TDR0,
+    NPCM7XX_TIMER_TDR1,
+    NPCM7XX_TIMER_TISR,
+    NPCM7XX_TIMER_WTCR,
+    NPCM7XX_TIMER_TCSR2,
+    NPCM7XX_TIMER_TCSR3,
+    NPCM7XX_TIMER_TICR2,
+    NPCM7XX_TIMER_TICR3,
+    NPCM7XX_TIMER_TDR2,
+    NPCM7XX_TIMER_TDR3,
+    NPCM7XX_TIMER_TCSR4         = 0x0040 / sizeof(uint32_t),
+    NPCM7XX_TIMER_TICR4         = 0x0048 / sizeof(uint32_t),
+    NPCM7XX_TIMER_TDR4          = 0x0050 / sizeof(uint32_t),
+    NPCM7XX_TIMER_REGS_END,
+};
+
+/* Register field definitions. */
+#define NPCM7XX_TCSR_CEN                BIT(30)
+#define NPCM7XX_TCSR_IE                 BIT(29)
+#define NPCM7XX_TCSR_PERIODIC           BIT(27)
+#define NPCM7XX_TCSR_CRST               BIT(26)
+#define NPCM7XX_TCSR_CACT               BIT(25)
+#define NPCM7XX_TCSR_RSVD               0x01ffff00
+#define NPCM7XX_TCSR_PRESCALE_START     0
+#define NPCM7XX_TCSR_PRESCALE_LEN       8
+
+/*
+ * Returns the index of timer in the tc->timer array. This can be used to
+ * locate the registers that belong to this timer.
+ */
+static int npcm7xx_timer_index(NPCM7xxTimerCtrlState *tc, NPCM7xxTimer *timer)
+{
+    int index = timer - tc->timer;
+
+    g_assert(index >= 0 && index < NPCM7XX_TIMERS_PER_CTRL);
+
+    return index;
+}
+
+/* Return the value by which to divide the reference clock rate. */
+static uint32_t npcm7xx_tcsr_prescaler(uint32_t tcsr)
+{
+    return extract32(tcsr, NPCM7XX_TCSR_PRESCALE_START,
+                     NPCM7XX_TCSR_PRESCALE_LEN) + 1;
+}
+
+/* Convert a timer cycle count to a time interval in nanoseconds. */
+static int64_t npcm7xx_timer_count_to_ns(NPCM7xxTimer *t, uint32_t count)
+{
+    int64_t ns = count;
+
+    ns *= NANOSECONDS_PER_SECOND / NPCM7XX_TIMER_REF_HZ;
+    ns *= npcm7xx_tcsr_prescaler(t->tcsr);
+
+    return ns;
+}
+
+/* Convert a time interval in nanoseconds to a timer cycle count. */
+static uint32_t npcm7xx_timer_ns_to_count(NPCM7xxTimer *t, int64_t ns)
+{
+    int64_t count;
+
+    count = ns / (NANOSECONDS_PER_SECOND / NPCM7XX_TIMER_REF_HZ);
+    count /= npcm7xx_tcsr_prescaler(t->tcsr);
+
+    return count;
+}
+
+/*
+ * Raise the interrupt line if there's a pending interrupt and interrupts are
+ * enabled for this timer. If not, lower it.
+ */
+static void npcm7xx_timer_check_interrupt(NPCM7xxTimer *t)
+{
+    NPCM7xxTimerCtrlState *tc = t->ctrl;
+    int index = npcm7xx_timer_index(tc, t);
+    bool pending = (t->tcsr & NPCM7XX_TCSR_IE) && (tc->tisr & BIT(index));
+
+    qemu_set_irq(t->irq, pending);
+    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.
+ */
+static void npcm7xx_timer_reached_zero(NPCM7xxTimer *t)
+{
+    NPCM7xxTimerCtrlState *tc = t->ctrl;
+    int index = npcm7xx_timer_index(tc, t);
+
+    tc->tisr |= BIT(index);
+
+    if (t->tcsr & NPCM7XX_TCSR_PERIODIC) {
+        t->remaining_ns = npcm7xx_timer_count_to_ns(t, t->ticr);
+        if (t->tcsr & NPCM7XX_TCSR_CEN) {
+            npcm7xx_timer_start(t);
+        }
+    } else {
+        t->tcsr &= ~(NPCM7XX_TCSR_CEN | NPCM7XX_TCSR_CACT);
+    }
+
+    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;
+    if (t->remaining_ns <= 0) {
+        npcm7xx_timer_reached_zero(t);
+    }
+}
+
+/*
+ * Restart the timer from its initial value. If the timer was enabled and stays
+ * enabled, adjust the QEMU timer according to the new count. If the timer is
+ * transitioning from disabled to enabled, the caller is expected to start the
+ * timer later.
+ */
+static void npcm7xx_timer_restart(NPCM7xxTimer *t, uint32_t old_tcsr)
+{
+    t->remaining_ns = npcm7xx_timer_count_to_ns(t, t->ticr);
+
+    if (old_tcsr & t->tcsr & NPCM7XX_TCSR_CEN) {
+        npcm7xx_timer_start(t);
+    }
+}
+
+/* Register read and write handlers */
+
+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->remaining_ns);
+}
+
+static void npcm7xx_timer_write_tcsr(NPCM7xxTimer *t, uint32_t new_tcsr)
+{
+    uint32_t old_tcsr = t->tcsr;
+    uint32_t tdr;
+
+    if (new_tcsr & NPCM7XX_TCSR_RSVD) {
+        qemu_log_mask(LOG_GUEST_ERROR, "%s: reserved bits in 0x%08x ignored\n",
+                      __func__, new_tcsr);
+        new_tcsr &= ~NPCM7XX_TCSR_RSVD;
+    }
+    if (new_tcsr & NPCM7XX_TCSR_CACT) {
+        qemu_log_mask(LOG_GUEST_ERROR, "%s: read-only bits in 0x%08x ignored\n",
+                      __func__, new_tcsr);
+        new_tcsr &= ~NPCM7XX_TCSR_CACT;
+    }
+    if ((new_tcsr & NPCM7XX_TCSR_CRST) && (new_tcsr & NPCM7XX_TCSR_CEN)) {
+        qemu_log_mask(LOG_GUEST_ERROR,
+                      "%s: both CRST and CEN set; ignoring CEN.\n",
+                      __func__);
+        new_tcsr &= ~NPCM7XX_TCSR_CEN;
+    }
+
+    /* Calculate the value of TDR before potentially changing the prescaler. */
+    tdr = npcm7xx_timer_read_tdr(t);
+
+    t->tcsr = (t->tcsr & NPCM7XX_TCSR_CACT) | 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);
+        if (old_tcsr & t->tcsr & NPCM7XX_TCSR_CEN) {
+            npcm7xx_timer_start(t);
+        }
+    }
+
+    if ((old_tcsr ^ new_tcsr) & NPCM7XX_TCSR_IE) {
+        npcm7xx_timer_check_interrupt(t);
+    }
+    if (new_tcsr & NPCM7XX_TCSR_CRST) {
+        npcm7xx_timer_restart(t, old_tcsr);
+        t->tcsr &= ~NPCM7XX_TCSR_CRST;
+    }
+    if ((old_tcsr ^ new_tcsr) & NPCM7XX_TCSR_CEN) {
+        if (new_tcsr & NPCM7XX_TCSR_CEN) {
+            t->tcsr |= NPCM7XX_TCSR_CACT;
+            npcm7xx_timer_start(t);
+        } else {
+            t->tcsr &= ~NPCM7XX_TCSR_CACT;
+            npcm7xx_timer_pause(t);
+        }
+    }
+}
+
+static void npcm7xx_timer_write_ticr(NPCM7xxTimer *t, uint32_t new_ticr)
+{
+    t->ticr = new_ticr;
+
+    npcm7xx_timer_restart(t, t->tcsr);
+}
+
+static void npcm7xx_timer_write_tisr(NPCM7xxTimerCtrlState *s, uint32_t value)
+{
+    int i;
+
+    s->tisr &= ~value;
+    for (i = 0; i < ARRAY_SIZE(s->timer); i++) {
+        if (value & (1U << i)) {
+            npcm7xx_timer_check_interrupt(&s->timer[i]);
+        }
+    }
+}
+
+static hwaddr npcm7xx_tcsr_index(hwaddr reg)
+{
+    switch (reg) {
+    case NPCM7XX_TIMER_TCSR0:
+        return 0;
+    case NPCM7XX_TIMER_TCSR1:
+        return 1;
+    case NPCM7XX_TIMER_TCSR2:
+        return 2;
+    case NPCM7XX_TIMER_TCSR3:
+        return 3;
+    case NPCM7XX_TIMER_TCSR4:
+        return 4;
+    default:
+        g_assert_not_reached();
+    }
+}
+
+static hwaddr npcm7xx_ticr_index(hwaddr reg)
+{
+    switch (reg) {
+    case NPCM7XX_TIMER_TICR0:
+        return 0;
+    case NPCM7XX_TIMER_TICR1:
+        return 1;
+    case NPCM7XX_TIMER_TICR2:
+        return 2;
+    case NPCM7XX_TIMER_TICR3:
+        return 3;
+    case NPCM7XX_TIMER_TICR4:
+        return 4;
+    default:
+        g_assert_not_reached();
+    }
+}
+
+static hwaddr npcm7xx_tdr_index(hwaddr reg)
+{
+    switch (reg) {
+    case NPCM7XX_TIMER_TDR0:
+        return 0;
+    case NPCM7XX_TIMER_TDR1:
+        return 1;
+    case NPCM7XX_TIMER_TDR2:
+        return 2;
+    case NPCM7XX_TIMER_TDR3:
+        return 3;
+    case NPCM7XX_TIMER_TDR4:
+        return 4;
+    default:
+        g_assert_not_reached();
+    }
+}
+
+static uint64_t npcm7xx_timer_read(void *opaque, hwaddr offset, unsigned size)
+{
+    NPCM7xxTimerCtrlState *s = opaque;
+    uint64_t value = 0;
+    hwaddr reg;
+
+    reg = offset / sizeof(uint32_t);
+    switch (reg) {
+    case NPCM7XX_TIMER_TCSR0:
+    case NPCM7XX_TIMER_TCSR1:
+    case NPCM7XX_TIMER_TCSR2:
+    case NPCM7XX_TIMER_TCSR3:
+    case NPCM7XX_TIMER_TCSR4:
+        value = s->timer[npcm7xx_tcsr_index(reg)].tcsr;
+        break;
+
+    case NPCM7XX_TIMER_TICR0:
+    case NPCM7XX_TIMER_TICR1:
+    case NPCM7XX_TIMER_TICR2:
+    case NPCM7XX_TIMER_TICR3:
+    case NPCM7XX_TIMER_TICR4:
+        value = s->timer[npcm7xx_ticr_index(reg)].ticr;
+        break;
+
+    case NPCM7XX_TIMER_TDR0:
+    case NPCM7XX_TIMER_TDR1:
+    case NPCM7XX_TIMER_TDR2:
+    case NPCM7XX_TIMER_TDR3:
+    case NPCM7XX_TIMER_TDR4:
+        value = npcm7xx_timer_read_tdr(&s->timer[npcm7xx_tdr_index(reg)]);
+        break;
+
+    case NPCM7XX_TIMER_TISR:
+        value = s->tisr;
+        break;
+
+    case NPCM7XX_TIMER_WTCR:
+        value = s->wtcr;
+        break;
+
+    default:
+        qemu_log_mask(LOG_GUEST_ERROR,
+                      "%s: invalid offset 0x%04" HWADDR_PRIx "\n",
+                      __func__, offset);
+        break;
+    }
+
+    trace_npcm7xx_timer_read(DEVICE(s)->canonical_path, offset, value);
+
+    return value;
+}
+
+static void npcm7xx_timer_write(void *opaque, hwaddr offset,
+                                uint64_t v, unsigned size)
+{
+    uint32_t reg = offset / sizeof(uint32_t);
+    NPCM7xxTimerCtrlState *s = opaque;
+    uint32_t value = v;
+
+    trace_npcm7xx_timer_write(DEVICE(s)->canonical_path, offset, value);
+
+    switch (reg) {
+    case NPCM7XX_TIMER_TCSR0:
+    case NPCM7XX_TIMER_TCSR1:
+    case NPCM7XX_TIMER_TCSR2:
+    case NPCM7XX_TIMER_TCSR3:
+    case NPCM7XX_TIMER_TCSR4:
+        npcm7xx_timer_write_tcsr(&s->timer[npcm7xx_tcsr_index(reg)], value);
+        return;
+
+    case NPCM7XX_TIMER_TICR0:
+    case NPCM7XX_TIMER_TICR1:
+    case NPCM7XX_TIMER_TICR2:
+    case NPCM7XX_TIMER_TICR3:
+    case NPCM7XX_TIMER_TICR4:
+        npcm7xx_timer_write_ticr(&s->timer[npcm7xx_ticr_index(reg)], value);
+        return;
+
+    case NPCM7XX_TIMER_TDR0:
+    case NPCM7XX_TIMER_TDR1:
+    case NPCM7XX_TIMER_TDR2:
+    case NPCM7XX_TIMER_TDR3:
+    case NPCM7XX_TIMER_TDR4:
+        qemu_log_mask(LOG_GUEST_ERROR,
+                      "%s: register @ 0x%04" HWADDR_PRIx " is read-only\n",
+                      __func__, offset);
+        return;
+
+    case NPCM7XX_TIMER_TISR:
+        npcm7xx_timer_write_tisr(s, value);
+        return;
+
+    case NPCM7XX_TIMER_WTCR:
+        qemu_log_mask(LOG_UNIMP, "%s: WTCR write not implemented: 0x%08x\n",
+                      __func__, value);
+        return;
+    }
+
+    qemu_log_mask(LOG_GUEST_ERROR,
+                  "%s: invalid offset 0x%04" HWADDR_PRIx "\n",
+                  __func__, offset);
+}
+
+static const struct MemoryRegionOps npcm7xx_timer_ops = {
+    .read       = npcm7xx_timer_read,
+    .write      = npcm7xx_timer_write,
+    .endianness = DEVICE_LITTLE_ENDIAN,
+    .valid      = {
+        .min_access_size        = 4,
+        .max_access_size        = 4,
+        .unaligned              = false,
+    },
+};
+
+/* Called when the QEMU timer expires. */
+static void npcm7xx_timer_expired(void *opaque)
+{
+    NPCM7xxTimer *t = opaque;
+
+    if (t->tcsr & NPCM7XX_TCSR_CEN) {
+        npcm7xx_timer_reached_zero(t);
+    }
+}
+
+static void npcm7xx_timer_enter_reset(Object *obj, ResetType type)
+{
+    NPCM7xxTimerCtrlState *s = NPCM7XX_TIMER(obj);
+    int i;
+
+    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;
+        t->tcsr = 0x00000005;
+        t->ticr = 0x00000000;
+    }
+
+    s->tisr = 0x00000000;
+    s->wtcr = 0x00000400;
+}
+
+static void npcm7xx_timer_hold_reset(Object *obj)
+{
+    NPCM7xxTimerCtrlState *s = NPCM7XX_TIMER(obj);
+    int i;
+
+    for (i = 0; i < NPCM7XX_TIMERS_PER_CTRL; i++) {
+        qemu_irq_lower(s->timer[i].irq);
+    }
+}
+
+static void npcm7xx_timer_realize(DeviceState *dev, Error **errp)
+{
+    NPCM7xxTimerCtrlState *s = NPCM7XX_TIMER(dev);
+    SysBusDevice *sbd = &s->parent;
+    int i;
+
+    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);
+        sysbus_init_irq(sbd, &t->irq);
+    }
+
+    memory_region_init_io(&s->iomem, OBJECT(s), &npcm7xx_timer_ops, s,
+                          TYPE_NPCM7XX_TIMER, 4 * KiB);
+    sysbus_init_mmio(sbd, &s->iomem);
+}
+
+static const VMStateDescription vmstate_npcm7xx_timer = {
+    .name = "npcm7xx-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_UINT32(tcsr, NPCM7xxTimer),
+        VMSTATE_UINT32(ticr, NPCM7xxTimer),
+        VMSTATE_END_OF_LIST(),
+    },
+};
+
+static const VMStateDescription vmstate_npcm7xx_timer_ctrl = {
+    .name = "npcm7xx-timer-ctrl",
+    .version_id = 0,
+    .minimum_version_id = 0,
+    .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_END_OF_LIST(),
+    },
+};
+
+static void npcm7xx_timer_class_init(ObjectClass *klass, void *data)
+{
+    ResettableClass *rc = RESETTABLE_CLASS(klass);
+    DeviceClass *dc = DEVICE_CLASS(klass);
+
+    QEMU_BUILD_BUG_ON(NPCM7XX_TIMER_REGS_END > NPCM7XX_TIMER_NR_REGS);
+
+    dc->desc = "NPCM7xx Timer Controller";
+    dc->realize = npcm7xx_timer_realize;
+    dc->vmsd = &vmstate_npcm7xx_timer_ctrl;
+    rc->phases.enter = npcm7xx_timer_enter_reset;
+    rc->phases.hold = npcm7xx_timer_hold_reset;
+}
+
+static const TypeInfo npcm7xx_timer_info = {
+    .name               = TYPE_NPCM7XX_TIMER,
+    .parent             = TYPE_SYS_BUS_DEVICE,
+    .instance_size      = sizeof(NPCM7xxTimerCtrlState),
+    .class_init         = npcm7xx_timer_class_init,
+};
+
+static void npcm7xx_timer_register_type(void)
+{
+    type_register_static(&npcm7xx_timer_info);
+}
+type_init(npcm7xx_timer_register_type);