qemu/hw/timer/bcm2835_systmr.c
Philippe Mathieu-Daudé be95dffa32 hw/timer/bcm2835: Support the timer COMPARE registers
This peripheral has 1 free-running timer and 4 compare registers.

Only the free-running timer is implemented. Add support the
COMPARE registers (each register is wired to an IRQ).

Reference: "BCM2835 ARM Peripherals" datasheet [*]
            chapter 12 "System Timer":

  The System Timer peripheral provides four 32-bit timer channels
  and a single 64-bit free running counter. Each channel has an
  output compare register, which is compared against the 32 least
  significant bits of the free running counter values. When the
  two values match, the system timer peripheral generates a signal
  to indicate a match for the appropriate channel. The match signal
  is then fed into the interrupt controller.

This peripheral is used since Linux 3.7, commit ee4af5696720
("ARM: bcm2835: add system timer").

[*] https://www.raspberrypi.org/app/uploads/2012/02/BCM2835-ARM-Peripherals.pdf

Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Luc Michel <luc@lmichel.fr>
Message-id: 20201010203709.3116542-4-f4bug@amsat.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
2020-10-20 16:12:00 +01:00

179 lines
5.2 KiB
C

/*
* BCM2835 SYS timer emulation
*
* Copyright (C) 2019 Philippe Mathieu-Daudé <f4bug@amsat.org>
*
* SPDX-License-Identifier: GPL-2.0-or-later
*
* Datasheet: BCM2835 ARM Peripherals (C6357-M-1398)
* https://www.raspberrypi.org/app/uploads/2012/02/BCM2835-ARM-Peripherals.pdf
*
* Only the free running 64-bit counter is implemented.
* The 4 COMPARE registers and the interruption are not implemented.
*/
#include "qemu/osdep.h"
#include "qemu/log.h"
#include "qemu/timer.h"
#include "hw/timer/bcm2835_systmr.h"
#include "hw/registerfields.h"
#include "migration/vmstate.h"
#include "trace.h"
REG32(CTRL_STATUS, 0x00)
REG32(COUNTER_LOW, 0x04)
REG32(COUNTER_HIGH, 0x08)
REG32(COMPARE0, 0x0c)
REG32(COMPARE1, 0x10)
REG32(COMPARE2, 0x14)
REG32(COMPARE3, 0x18)
static void bcm2835_systmr_timer_expire(void *opaque)
{
BCM2835SystemTimerCompare *tmr = opaque;
trace_bcm2835_systmr_timer_expired(tmr->id);
tmr->state->reg.ctrl_status |= 1 << tmr->id;
qemu_set_irq(tmr->irq, 1);
}
static uint64_t bcm2835_systmr_read(void *opaque, hwaddr offset,
unsigned size)
{
BCM2835SystemTimerState *s = BCM2835_SYSTIMER(opaque);
uint64_t r = 0;
switch (offset) {
case A_CTRL_STATUS:
r = s->reg.ctrl_status;
break;
case A_COMPARE0 ... A_COMPARE3:
r = s->reg.compare[(offset - A_COMPARE0) >> 2];
break;
case A_COUNTER_LOW:
case A_COUNTER_HIGH:
/* Free running counter at 1MHz */
r = qemu_clock_get_us(QEMU_CLOCK_VIRTUAL);
r >>= 8 * (offset - A_COUNTER_LOW);
r &= UINT32_MAX;
break;
default:
qemu_log_mask(LOG_GUEST_ERROR, "%s: bad offset 0x%" HWADDR_PRIx "\n",
__func__, offset);
break;
}
trace_bcm2835_systmr_read(offset, r);
return r;
}
static void bcm2835_systmr_write(void *opaque, hwaddr offset,
uint64_t value64, unsigned size)
{
BCM2835SystemTimerState *s = BCM2835_SYSTIMER(opaque);
int index;
uint32_t value = value64;
uint32_t triggers_delay_us;
uint64_t now;
trace_bcm2835_systmr_write(offset, value);
switch (offset) {
case A_CTRL_STATUS:
s->reg.ctrl_status &= ~value; /* Ack */
for (index = 0; index < ARRAY_SIZE(s->tmr); index++) {
if (extract32(value, index, 1)) {
trace_bcm2835_systmr_irq_ack(index);
qemu_set_irq(s->tmr[index].irq, 0);
}
}
break;
case A_COMPARE0 ... A_COMPARE3:
index = (offset - A_COMPARE0) >> 2;
s->reg.compare[index] = value;
now = qemu_clock_get_us(QEMU_CLOCK_VIRTUAL);
/* Compare lower 32-bits of the free-running counter. */
triggers_delay_us = value - now;
trace_bcm2835_systmr_run(index, triggers_delay_us);
timer_mod(&s->tmr[index].timer, now + triggers_delay_us);
break;
case A_COUNTER_LOW:
case A_COUNTER_HIGH:
qemu_log_mask(LOG_GUEST_ERROR, "%s: read-only ofs 0x%" HWADDR_PRIx "\n",
__func__, offset);
break;
default:
qemu_log_mask(LOG_GUEST_ERROR, "%s: bad offset 0x%" HWADDR_PRIx "\n",
__func__, offset);
break;
}
}
static const MemoryRegionOps bcm2835_systmr_ops = {
.read = bcm2835_systmr_read,
.write = bcm2835_systmr_write,
.endianness = DEVICE_LITTLE_ENDIAN,
.impl = {
.min_access_size = 4,
.max_access_size = 4,
},
};
static void bcm2835_systmr_reset(DeviceState *dev)
{
BCM2835SystemTimerState *s = BCM2835_SYSTIMER(dev);
memset(&s->reg, 0, sizeof(s->reg));
}
static void bcm2835_systmr_realize(DeviceState *dev, Error **errp)
{
BCM2835SystemTimerState *s = BCM2835_SYSTIMER(dev);
memory_region_init_io(&s->iomem, OBJECT(dev), &bcm2835_systmr_ops,
s, "bcm2835-sys-timer", 0x20);
sysbus_init_mmio(SYS_BUS_DEVICE(dev), &s->iomem);
for (size_t i = 0; i < ARRAY_SIZE(s->tmr); i++) {
s->tmr[i].id = i;
s->tmr[i].state = s;
sysbus_init_irq(SYS_BUS_DEVICE(dev), &s->tmr[i].irq);
timer_init_us(&s->tmr[i].timer, QEMU_CLOCK_VIRTUAL,
bcm2835_systmr_timer_expire, &s->tmr[i]);
}
}
static const VMStateDescription bcm2835_systmr_vmstate = {
.name = "bcm2835_sys_timer",
.version_id = 1,
.minimum_version_id = 1,
.fields = (VMStateField[]) {
VMSTATE_UINT32(reg.ctrl_status, BCM2835SystemTimerState),
VMSTATE_UINT32_ARRAY(reg.compare, BCM2835SystemTimerState,
BCM2835_SYSTIMER_COUNT),
VMSTATE_END_OF_LIST()
}
};
static void bcm2835_systmr_class_init(ObjectClass *klass, void *data)
{
DeviceClass *dc = DEVICE_CLASS(klass);
dc->realize = bcm2835_systmr_realize;
dc->reset = bcm2835_systmr_reset;
dc->vmsd = &bcm2835_systmr_vmstate;
}
static const TypeInfo bcm2835_systmr_info = {
.name = TYPE_BCM2835_SYSTIMER,
.parent = TYPE_SYS_BUS_DEVICE,
.instance_size = sizeof(BCM2835SystemTimerState),
.class_init = bcm2835_systmr_class_init,
};
static void bcm2835_systmr_register_types(void)
{
type_register_static(&bcm2835_systmr_info);
}
type_init(bcm2835_systmr_register_types);