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hw/timer/armv7m_systick: Use clock inputs instead of system_clock_scale 

Now that all users of the systick devices wire up the clock inputs,
use those instead of the system_clock_scale and the hardwired 1MHz
value for the reference clock.

This will fix various board models where we were incorrectly
providing a 1MHz reference clock instead of some other value or
instead of providing no reference clock at all.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Damien Hedde <damien.hedde@greensocs.com>
Message-id: 20210812093356.1946-22-peter.maydell@linaro.org
This commit is contained in:
Peter Maydell 2021-08-12 10:33:52 +01:00
parent 3b76e18520
commit a40e10f1dc
1 changed files with 84 additions and 28 deletions
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112
hw/timer/armv7m_systick.c
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@ -18,25 +18,30 @@
#include "qemu/timer.h"
#include "qemu/log.h"
#include "qemu/module.h"
#include "qapi/error.h"
#include "trace.h"
/* qemu timers run at 1GHz. We want something closer to 1MHz. */
#define SYSTICK_SCALE 1000ULL
#define SYSTICK_ENABLE (1 << 0)
#define SYSTICK_TICKINT (1 << 1)
#define SYSTICK_CLKSOURCE (1 << 2)
#define SYSTICK_COUNTFLAG (1 << 16)
#define SYSCALIB_NOREF (1U << 31)
#define SYSCALIB_SKEW (1U << 30)
#define SYSCALIB_TENMS ((1U << 24) - 1)
int system_clock_scale;
/* Conversion factor from qemu timer to SysTick frequencies. */
static inline int64_t systick_scale(SysTickState *s)
static void systick_set_period_from_clock(SysTickState *s)
{
/*
* Set the ptimer period from whichever clock is selected.
* Must be called from within a ptimer transaction block.
*/
if (s->control & SYSTICK_CLKSOURCE) {
return system_clock_scale;
ptimer_set_period_from_clock(s->ptimer, s->cpuclk, 1);
} else {
return 1000;
ptimer_set_period_from_clock(s->ptimer, s->refclk, 1);
}
}
@ -83,7 +88,28 @@ static MemTxResult systick_read(void *opaque, hwaddr addr, uint64_t *data,
val = ptimer_get_count(s->ptimer);
break;
case 0xc: /* SysTick Calibration Value. */
val = 10000;
/*
* In real hardware it is possible to make this register report
* a different value from what the reference clock is actually
* running at. We don't model that (which usually happens due
* to integration errors in the real hardware) and instead always
* report the theoretical correct value as described in the
* knowledgebase article at
* https://developer.arm.com/documentation/ka001325/latest
* If necessary, we could implement an extra QOM property on this
* device to force the STCALIB value to something different from
* the "correct" value.
*/
if (!clock_has_source(s->refclk)) {
val = SYSCALIB_NOREF;
break;
}
val = clock_ns_to_ticks(s->refclk, 10 * SCALE_MS) - 1;
val &= SYSCALIB_TENMS;
if (clock_ticks_to_ns(s->refclk, val + 1) != 10 * SCALE_MS) {
/* report that tick count does not yield exactly 10ms */
val |= SYSCALIB_SKEW;
}
break;
default:
val = 0;
@ -115,6 +141,11 @@ static MemTxResult systick_write(void *opaque, hwaddr addr,
{
uint32_t oldval;
if (!clock_has_source(s->refclk)) {
/* This bit is always 1 if there is no external refclk */
value |= SYSTICK_CLKSOURCE;
}
ptimer_transaction_begin(s->ptimer);
oldval = s->control;
s->control &= 0xfffffff8;
@ -122,19 +153,14 @@ static MemTxResult systick_write(void *opaque, hwaddr addr,
if ((oldval ^ value) & SYSTICK_ENABLE) {
if (value & SYSTICK_ENABLE) {
/*
* Always reload the period in case board code has
* changed system_clock_scale. If we ever replace that
* global with a more sensible API then we might be able
* to set the period only when it actually changes.
*/
ptimer_set_period(s->ptimer, systick_scale(s));
ptimer_run(s->ptimer, 0);
} else {
ptimer_stop(s->ptimer);
}
} else if ((oldval ^ value) & SYSTICK_CLKSOURCE) {
ptimer_set_period(s->ptimer, systick_scale(s));
}
if ((oldval ^ value) & SYSTICK_CLKSOURCE) {
systick_set_period_from_clock(s);
}
ptimer_transaction_commit(s->ptimer);
break;
@ -177,20 +203,42 @@ static void systick_reset(DeviceState *dev)
{
SysTickState *s = SYSTICK(dev);
/*
* Forgetting to set system_clock_scale is always a board code
* bug. We can't check this earlier because for some boards
* (like stellaris) it is not yet configured at the point where
* the systick device is realized.
*/
assert(system_clock_scale != 0);
ptimer_transaction_begin(s->ptimer);
s->control = 0;
if (!clock_has_source(s->refclk)) {
/* This bit is always 1 if there is no external refclk */
s->control |= SYSTICK_CLKSOURCE;
}
ptimer_stop(s->ptimer);
ptimer_set_count(s->ptimer, 0);
ptimer_set_limit(s->ptimer, 0, 0);
ptimer_set_period(s->ptimer, systick_scale(s));
systick_set_period_from_clock(s);
ptimer_transaction_commit(s->ptimer);
}
static void systick_cpuclk_update(void *opaque, ClockEvent event)
{
SysTickState *s = SYSTICK(opaque);
if (!(s->control & SYSTICK_CLKSOURCE)) {
/* currently using refclk, we can ignore cpuclk changes */
}
ptimer_transaction_begin(s->ptimer);
ptimer_set_period_from_clock(s->ptimer, s->cpuclk, 1);
ptimer_transaction_commit(s->ptimer);
}
static void systick_refclk_update(void *opaque, ClockEvent event)
{
SysTickState *s = SYSTICK(opaque);
if (s->control & SYSTICK_CLKSOURCE) {
/* currently using cpuclk, we can ignore refclk changes */
}
ptimer_transaction_begin(s->ptimer);
ptimer_set_period_from_clock(s->ptimer, s->refclk, 1);
ptimer_transaction_commit(s->ptimer);
}
@ -203,8 +251,10 @@ static void systick_instance_init(Object *obj)
sysbus_init_mmio(sbd, &s->iomem);
sysbus_init_irq(sbd, &s->irq);
s->refclk = qdev_init_clock_in(DEVICE(obj), "refclk", NULL, NULL, 0);
s->cpuclk = qdev_init_clock_in(DEVICE(obj), "cpuclk", NULL, NULL, 0);
s->refclk = qdev_init_clock_in(DEVICE(obj), "refclk",
systick_refclk_update, s, ClockUpdate);
s->cpuclk = qdev_init_clock_in(DEVICE(obj), "cpuclk",
systick_cpuclk_update, s, ClockUpdate);
}
static void systick_realize(DeviceState *dev, Error **errp)
@ -215,6 +265,12 @@ static void systick_realize(DeviceState *dev, Error **errp)
PTIMER_POLICY_NO_COUNTER_ROUND_DOWN |
PTIMER_POLICY_NO_IMMEDIATE_RELOAD |
PTIMER_POLICY_TRIGGER_ONLY_ON_DECREMENT);
if (!clock_has_source(s->cpuclk)) {
error_setg(errp, "systick: cpuclk must be connected");
return;
}
/* It's OK not to connect the refclk */
}
static const VMStateDescription vmstate_systick = {