qemu/hw/timer/imx_epit.c
Axel Heider 8d71beaf1e hw/timer/imx_epit: fix compare timer handling
- fix #1263 for CR writes
- rework compare time handling
  - The compare timer has to run even if CR.OCIEN is not set,
    as SR.OCIF must be updated.
  - The compare timer fires exactly once when the
    compare value is less than the current value, but the
    reload values is less than the compare value.
  - The compare timer will never fire if the reload value is
    less than the compare value. Disable it in this case.

Signed-off-by: Axel Heider <axel.heider@hensoldt.net>
[PMM: fixed minor style nits]
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
2023-01-05 12:14:43 +00:00

453 lines
14 KiB
C

/*
* IMX EPIT Timer
*
* Copyright (c) 2008 OK Labs
* Copyright (c) 2011 NICTA Pty Ltd
* Originally written by Hans Jiang
* Updated by Peter Chubb
* Updated by Jean-Christophe Dubois <jcd@tribudubois.net>
* Updated by Axel Heider
*
* This code is licensed under GPL version 2 or later. See
* the COPYING file in the top-level directory.
*
*/
#include "qemu/osdep.h"
#include "hw/timer/imx_epit.h"
#include "migration/vmstate.h"
#include "hw/irq.h"
#include "hw/misc/imx_ccm.h"
#include "qemu/module.h"
#include "qemu/log.h"
#ifndef DEBUG_IMX_EPIT
#define DEBUG_IMX_EPIT 0
#endif
#define DPRINTF(fmt, args...) \
do { \
if (DEBUG_IMX_EPIT) { \
fprintf(stderr, "[%s]%s: " fmt , TYPE_IMX_EPIT, \
__func__, ##args); \
} \
} while (0)
static const char *imx_epit_reg_name(uint32_t reg)
{
switch (reg) {
case 0:
return "CR";
case 1:
return "SR";
case 2:
return "LR";
case 3:
return "CMP";
case 4:
return "CNT";
default:
return "[?]";
}
}
/*
* Exact clock frequencies vary from board to board.
* These are typical.
*/
static const IMXClk imx_epit_clocks[] = {
CLK_NONE, /* 00 disabled */
CLK_IPG, /* 01 ipg_clk, ~532MHz */
CLK_IPG_HIGH, /* 10 ipg_clk_highfreq */
CLK_32k, /* 11 ipg_clk_32k -- ~32kHz */
};
/*
* Update interrupt status
*/
static void imx_epit_update_int(IMXEPITState *s)
{
if ((s->sr & SR_OCIF) && (s->cr & CR_OCIEN) && (s->cr & CR_EN)) {
qemu_irq_raise(s->irq);
} else {
qemu_irq_lower(s->irq);
}
}
static uint32_t imx_epit_get_freq(IMXEPITState *s)
{
uint32_t clksrc = extract32(s->cr, CR_CLKSRC_SHIFT, CR_CLKSRC_BITS);
uint32_t prescaler = 1 + extract32(s->cr, CR_PRESCALE_SHIFT, CR_PRESCALE_BITS);
uint32_t f_in = imx_ccm_get_clock_frequency(s->ccm, imx_epit_clocks[clksrc]);
uint32_t freq = f_in / prescaler;
DPRINTF("ptimer frequency is %u\n", freq);
return freq;
}
/*
* This is called both on hardware (device) reset and software reset.
*/
static void imx_epit_reset(IMXEPITState *s, bool is_hard_reset)
{
/* Soft reset doesn't touch some bits; hard reset clears them */
if (is_hard_reset) {
s->cr = 0;
} else {
s->cr &= (CR_EN|CR_ENMOD|CR_STOPEN|CR_DOZEN|CR_WAITEN|CR_DBGEN);
}
s->sr = 0;
s->lr = EPIT_TIMER_MAX;
s->cmp = 0;
ptimer_transaction_begin(s->timer_cmp);
ptimer_transaction_begin(s->timer_reload);
/*
* The reset switches off the input clock, so even if the CR.EN is still
* set, the timers are no longer running.
*/
assert(imx_epit_get_freq(s) == 0);
ptimer_stop(s->timer_cmp);
ptimer_stop(s->timer_reload);
/* init both timers to EPIT_TIMER_MAX */
ptimer_set_limit(s->timer_cmp, EPIT_TIMER_MAX, 1);
ptimer_set_limit(s->timer_reload, EPIT_TIMER_MAX, 1);
ptimer_transaction_commit(s->timer_cmp);
ptimer_transaction_commit(s->timer_reload);
}
static uint64_t imx_epit_read(void *opaque, hwaddr offset, unsigned size)
{
IMXEPITState *s = IMX_EPIT(opaque);
uint32_t reg_value = 0;
switch (offset >> 2) {
case 0: /* Control Register */
reg_value = s->cr;
break;
case 1: /* Status Register */
reg_value = s->sr;
break;
case 2: /* LR - ticks*/
reg_value = s->lr;
break;
case 3: /* CMP */
reg_value = s->cmp;
break;
case 4: /* CNT */
reg_value = ptimer_get_count(s->timer_reload);
break;
default:
qemu_log_mask(LOG_GUEST_ERROR, "[%s]%s: Bad register at offset 0x%"
HWADDR_PRIx "\n", TYPE_IMX_EPIT, __func__, offset);
break;
}
DPRINTF("(%s) = 0x%08x\n", imx_epit_reg_name(offset >> 2), reg_value);
return reg_value;
}
/*
* Must be called from a ptimer_transaction_begin/commit block for
* s->timer_cmp, but outside of a transaction block of s->timer_reload,
* so the proper counter value is read.
*/
static void imx_epit_update_compare_timer(IMXEPITState *s)
{
uint64_t counter = 0;
bool is_oneshot = false;
/*
* The compare timer only has to run if the timer peripheral is active
* and there is an input clock, Otherwise it can be switched off.
*/
bool is_active = (s->cr & CR_EN) && imx_epit_get_freq(s);
if (is_active) {
/*
* Calculate next timeout for compare timer. Reading the reload
* counter returns proper results only if pending transactions
* on it are committed here. Otherwise stale values are be read.
*/
counter = ptimer_get_count(s->timer_reload);
uint64_t limit = ptimer_get_limit(s->timer_cmp);
/*
* The compare timer is a periodic timer if the limit is at least
* the compare value. Otherwise it may fire at most once in the
* current round.
*/
bool is_oneshot = (limit >= s->cmp);
if (counter >= s->cmp) {
/* The compare timer fires in the current round. */
counter -= s->cmp;
} else if (!is_oneshot) {
/*
* The compare timer fires after a reload, as it is below the
* compare value already in this round. Note that the counter
* value calculated below can be above the 32-bit limit, which
* is legal here because the compare timer is an internal
* helper ptimer only.
*/
counter += limit - s->cmp;
} else {
/*
* The compare timer won't fire in this round, and the limit is
* set to a value below the compare value. This practically means
* it will never fire, so it can be switched off.
*/
is_active = false;
}
}
/*
* Set the compare timer and let it run, or stop it. This is agnostic
* of CR.OCIEN bit, as this bit affects interrupt generation only. The
* compare timer needs to run even if no interrupts are to be generated,
* because the SR.OCIF bit must be updated also.
* Note that the timer might already be stopped or be running with
* counter values. However, finding out when an update is needed and
* when not is not trivial. It's much easier applying the setting again,
* as this does not harm either and the overhead is negligible.
*/
if (is_active) {
ptimer_set_count(s->timer_cmp, counter);
ptimer_run(s->timer_cmp, is_oneshot ? 1 : 0);
} else {
ptimer_stop(s->timer_cmp);
}
}
static void imx_epit_write_cr(IMXEPITState *s, uint32_t value)
{
uint32_t oldcr = s->cr;
s->cr = value & 0x03ffffff;
if (s->cr & CR_SWR) {
/*
* Reset clears CR.SWR again. It does not touch CR.EN, but the timers
* are still stopped because the input clock is disabled.
*/
imx_epit_reset(s, false);
} else {
uint32_t freq;
uint32_t toggled_cr_bits = oldcr ^ s->cr;
/* re-initialize the limits if CR.RLD has changed */
bool set_limit = toggled_cr_bits & CR_RLD;
/* set the counter if the timer got just enabled and CR.ENMOD is set */
bool is_switched_on = (toggled_cr_bits & s->cr) & CR_EN;
bool set_counter = is_switched_on && (s->cr & CR_ENMOD);
ptimer_transaction_begin(s->timer_cmp);
ptimer_transaction_begin(s->timer_reload);
freq = imx_epit_get_freq(s);
if (freq) {
ptimer_set_freq(s->timer_reload, freq);
ptimer_set_freq(s->timer_cmp, freq);
}
if (set_limit || set_counter) {
uint64_t limit = (s->cr & CR_RLD) ? s->lr : EPIT_TIMER_MAX;
ptimer_set_limit(s->timer_reload, limit, set_counter ? 1 : 0);
if (set_limit) {
ptimer_set_limit(s->timer_cmp, limit, 0);
}
}
/*
* If there is an input clock and the peripheral is enabled, then
* ensure the wall clock timer is ticking. Otherwise stop the timers.
* The compare timer will be updated later.
*/
if (freq && (s->cr & CR_EN)) {
ptimer_run(s->timer_reload, 0);
} else {
ptimer_stop(s->timer_reload);
}
/* Commit changes to reload timer, so they can propagate. */
ptimer_transaction_commit(s->timer_reload);
/* Update compare timer based on the committed reload timer value. */
imx_epit_update_compare_timer(s);
ptimer_transaction_commit(s->timer_cmp);
}
/*
* The interrupt state can change due to:
* - reset clears both SR.OCIF and CR.OCIE
* - write to CR.EN or CR.OCIE
*/
imx_epit_update_int(s);
}
static void imx_epit_write_sr(IMXEPITState *s, uint32_t value)
{
/* writing 1 to SR.OCIF clears this bit and turns the interrupt off */
if (value & SR_OCIF) {
s->sr = 0; /* SR.OCIF is the only bit in this register anyway */
imx_epit_update_int(s);
}
}
static void imx_epit_write_lr(IMXEPITState *s, uint32_t value)
{
s->lr = value;
ptimer_transaction_begin(s->timer_cmp);
ptimer_transaction_begin(s->timer_reload);
if (s->cr & CR_RLD) {
/* Also set the limit if the LRD bit is set */
/* If IOVW bit is set then set the timer value */
ptimer_set_limit(s->timer_reload, s->lr, s->cr & CR_IOVW);
ptimer_set_limit(s->timer_cmp, s->lr, 0);
} else if (s->cr & CR_IOVW) {
/* If IOVW bit is set then set the timer value */
ptimer_set_count(s->timer_reload, s->lr);
}
/* Commit the changes to s->timer_reload, so they can propagate. */
ptimer_transaction_commit(s->timer_reload);
/* Update the compare timer based on the committed reload timer value. */
imx_epit_update_compare_timer(s);
ptimer_transaction_commit(s->timer_cmp);
}
static void imx_epit_write_cmp(IMXEPITState *s, uint32_t value)
{
s->cmp = value;
/* Update the compare timer based on the committed reload timer value. */
ptimer_transaction_begin(s->timer_cmp);
imx_epit_update_compare_timer(s);
ptimer_transaction_commit(s->timer_cmp);
}
static void imx_epit_write(void *opaque, hwaddr offset, uint64_t value,
unsigned size)
{
IMXEPITState *s = IMX_EPIT(opaque);
DPRINTF("(%s, value = 0x%08x)\n", imx_epit_reg_name(offset >> 2),
(uint32_t)value);
switch (offset >> 2) {
case 0: /* CR */
imx_epit_write_cr(s, (uint32_t)value);
break;
case 1: /* SR */
imx_epit_write_sr(s, (uint32_t)value);
break;
case 2: /* LR */
imx_epit_write_lr(s, (uint32_t)value);
break;
case 3: /* CMP */
imx_epit_write_cmp(s, (uint32_t)value);
break;
default:
qemu_log_mask(LOG_GUEST_ERROR, "[%s]%s: Bad register at offset 0x%"
HWADDR_PRIx "\n", TYPE_IMX_EPIT, __func__, offset);
break;
}
}
static void imx_epit_cmp(void *opaque)
{
IMXEPITState *s = IMX_EPIT(opaque);
/* The cmp ptimer can't be running when the peripheral is disabled */
assert(s->cr & CR_EN);
DPRINTF("sr was %d\n", s->sr);
/* Set interrupt status bit SR.OCIF and update the interrupt state */
s->sr |= SR_OCIF;
imx_epit_update_int(s);
}
static void imx_epit_reload(void *opaque)
{
/* No action required on rollover of timer_reload */
}
static const MemoryRegionOps imx_epit_ops = {
.read = imx_epit_read,
.write = imx_epit_write,
.endianness = DEVICE_NATIVE_ENDIAN,
};
static const VMStateDescription vmstate_imx_timer_epit = {
.name = TYPE_IMX_EPIT,
.version_id = 3,
.minimum_version_id = 3,
.fields = (VMStateField[]) {
VMSTATE_UINT32(cr, IMXEPITState),
VMSTATE_UINT32(sr, IMXEPITState),
VMSTATE_UINT32(lr, IMXEPITState),
VMSTATE_UINT32(cmp, IMXEPITState),
VMSTATE_PTIMER(timer_reload, IMXEPITState),
VMSTATE_PTIMER(timer_cmp, IMXEPITState),
VMSTATE_END_OF_LIST()
}
};
static void imx_epit_realize(DeviceState *dev, Error **errp)
{
IMXEPITState *s = IMX_EPIT(dev);
SysBusDevice *sbd = SYS_BUS_DEVICE(dev);
DPRINTF("\n");
sysbus_init_irq(sbd, &s->irq);
memory_region_init_io(&s->iomem, OBJECT(s), &imx_epit_ops, s, TYPE_IMX_EPIT,
0x00001000);
sysbus_init_mmio(sbd, &s->iomem);
/*
* The reload timer keeps running when the peripheral is enabled. It is a
* kind of wall clock that does not generate any interrupts. The callback
* needs to be provided, but it does nothing as the ptimer already supports
* all necessary reloading functionality.
*/
s->timer_reload = ptimer_init(imx_epit_reload, s, PTIMER_POLICY_LEGACY);
/*
* The compare timer is running only when the peripheral configuration is
* in a state that will generate compare interrupts.
*/
s->timer_cmp = ptimer_init(imx_epit_cmp, s, PTIMER_POLICY_LEGACY);
}
static void imx_epit_dev_reset(DeviceState *dev)
{
IMXEPITState *s = IMX_EPIT(dev);
imx_epit_reset(s, true);
}
static void imx_epit_class_init(ObjectClass *klass, void *data)
{
DeviceClass *dc = DEVICE_CLASS(klass);
dc->realize = imx_epit_realize;
dc->reset = imx_epit_dev_reset;
dc->vmsd = &vmstate_imx_timer_epit;
dc->desc = "i.MX periodic timer";
}
static const TypeInfo imx_epit_info = {
.name = TYPE_IMX_EPIT,
.parent = TYPE_SYS_BUS_DEVICE,
.instance_size = sizeof(IMXEPITState),
.class_init = imx_epit_class_init,
};
static void imx_epit_register_types(void)
{
type_register_static(&imx_epit_info);
}
type_init(imx_epit_register_types)