diff options
Diffstat (limited to 'hw/timer/armv7m_systick.c')
| -rw-r--r-- | hw/timer/armv7m_systick.c | 118 |
1 files changed, 89 insertions, 29 deletions
diff --git a/hw/timer/armv7m_systick.c b/hw/timer/armv7m_systick.c index 2f192011eb..3bd951dd04 100644 --- a/hw/timer/armv7m_systick.c +++ b/hw/timer/armv7m_systick.c @@ -14,28 +14,32 @@ #include "migration/vmstate.h" #include "hw/irq.h" #include "hw/sysbus.h" +#include "hw/qdev-clock.h" #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) -int system_clock_scale; +#define SYSCALIB_NOREF (1U << 31) +#define SYSCALIB_SKEW (1U << 30) +#define SYSCALIB_TENMS ((1U << 24) - 1) -/* 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); } } @@ -82,7 +86,28 @@ 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; @@ -114,6 +139,11 @@ 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; @@ -121,19 +151,14 @@ 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; @@ -176,20 +201,42 @@ 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); } @@ -201,6 +248,11 @@ static void systick_instance_init(Object *obj) memory_region_init_io(&s->iomem, obj, &systick_ops, s, "systick", 0xe0); sysbus_init_mmio(sbd, &s->iomem); sysbus_init_irq(sbd, &s->irq); + + 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) @@ -211,13 +263,21 @@ 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 = { .name = "armv7m_systick", - .version_id = 2, - .minimum_version_id = 2, + .version_id = 3, + .minimum_version_id = 3, .fields = (VMStateField[]) { + VMSTATE_CLOCK(refclk, SysTickState), + VMSTATE_CLOCK(cpuclk, SysTickState), VMSTATE_UINT32(control, SysTickState), VMSTATE_INT64(tick, SysTickState), VMSTATE_PTIMER(ptimer, SysTickState), |