/* * ARMv7M SysTick timer * * Copyright (c) 2006-2007 CodeSourcery. * Written by Paul Brook * Copyright (c) 2017 Linaro Ltd * Written by Peter Maydell * * This code is licensed under the GPL (version 2 or later). */ #include "qemu/osdep.h" #include "hw/timer/armv7m_systick.h" #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 "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; /* Conversion factor from qemu timer to SysTick frequencies. */ static inline int64_t systick_scale(SysTickState *s) { if (s->control & SYSTICK_CLKSOURCE) { return system_clock_scale; } else { return 1000; } } static void systick_timer_tick(void *opaque) { SysTickState *s = (SysTickState *)opaque; trace_systick_timer_tick(); s->control |= SYSTICK_COUNTFLAG; if (s->control & SYSTICK_TICKINT) { /* Tell the NVIC to pend the SysTick exception */ qemu_irq_pulse(s->irq); } if (ptimer_get_limit(s->ptimer) == 0) { /* * Timer expiry with SYST_RVR zero disables the timer * (but doesn't clear SYST_CSR.ENABLE) */ ptimer_stop(s->ptimer); } } static MemTxResult systick_read(void *opaque, hwaddr addr, uint64_t *data, unsigned size, MemTxAttrs attrs) { SysTickState *s = opaque; uint32_t val; if (attrs.user) { /* Generate BusFault for unprivileged accesses */ return MEMTX_ERROR; } switch (addr) { case 0x0: /* SysTick Control and Status. */ val = s->control; s->control &= ~SYSTICK_COUNTFLAG; break; case 0x4: /* SysTick Reload Value. */ val = ptimer_get_limit(s->ptimer); break; case 0x8: /* SysTick Current Value. */ val = ptimer_get_count(s->ptimer); break; case 0xc: /* SysTick Calibration Value. */ val = 10000; break; default: val = 0; qemu_log_mask(LOG_GUEST_ERROR, "SysTick: Bad read offset 0x%" HWADDR_PRIx "\n", addr); break; } trace_systick_read(addr, val, size); *data = val; return MEMTX_OK; } static MemTxResult systick_write(void *opaque, hwaddr addr, uint64_t value, unsigned size, MemTxAttrs attrs) { SysTickState *s = opaque; if (attrs.user) { /* Generate BusFault for unprivileged accesses */ return MEMTX_ERROR; } trace_systick_write(addr, value, size); switch (addr) { case 0x0: /* SysTick Control and Status. */ { uint32_t oldval; ptimer_transaction_begin(s->ptimer); oldval = s->control; s->control &= 0xfffffff8; s->control |= value & 7; 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)); } ptimer_transaction_commit(s->ptimer); break; } case 0x4: /* SysTick Reload Value. */ ptimer_transaction_begin(s->ptimer); ptimer_set_limit(s->ptimer, value & 0xffffff, 0); ptimer_transaction_commit(s->ptimer); break; case 0x8: /* SysTick Current Value. */ /* * Writing any value clears SYST_CVR to zero and clears * SYST_CSR.COUNTFLAG. The counter will then reload from SYST_RVR * on the next clock edge unless SYST_RVR is zero. */ ptimer_transaction_begin(s->ptimer); if (ptimer_get_limit(s->ptimer) == 0) { ptimer_stop(s->ptimer); } ptimer_set_count(s->ptimer, 0); s->control &= ~SYSTICK_COUNTFLAG; ptimer_transaction_commit(s->ptimer); break; default: qemu_log_mask(LOG_GUEST_ERROR, "SysTick: Bad write offset 0x%" HWADDR_PRIx "\n", addr); } return MEMTX_OK; } static const MemoryRegionOps systick_ops = { .read_with_attrs = systick_read, .write_with_attrs = systick_write, .endianness = DEVICE_NATIVE_ENDIAN, .valid.min_access_size = 4, .valid.max_access_size = 4, }; 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; 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)); ptimer_transaction_commit(s->ptimer); } static void systick_instance_init(Object *obj) { SysBusDevice *sbd = SYS_BUS_DEVICE(obj); SysTickState *s = SYSTICK(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", NULL, NULL, 0); s->cpuclk = qdev_init_clock_in(DEVICE(obj), "cpuclk", NULL, NULL, 0); } static void systick_realize(DeviceState *dev, Error **errp) { SysTickState *s = SYSTICK(dev); s->ptimer = ptimer_init(systick_timer_tick, s, PTIMER_POLICY_WRAP_AFTER_ONE_PERIOD | PTIMER_POLICY_NO_COUNTER_ROUND_DOWN | PTIMER_POLICY_NO_IMMEDIATE_RELOAD | PTIMER_POLICY_TRIGGER_ONLY_ON_DECREMENT); } static const VMStateDescription vmstate_systick = { .name = "armv7m_systick", .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), VMSTATE_END_OF_LIST() } }; static void systick_class_init(ObjectClass *klass, void *data) { DeviceClass *dc = DEVICE_CLASS(klass); dc->vmsd = &vmstate_systick; dc->reset = systick_reset; dc->realize = systick_realize; } static const TypeInfo armv7m_systick_info = { .name = TYPE_SYSTICK, .parent = TYPE_SYS_BUS_DEVICE, .instance_init = systick_instance_init, .instance_size = sizeof(SysTickState), .class_init = systick_class_init, }; static void armv7m_systick_register_types(void) { type_register_static(&armv7m_systick_info); } type_init(armv7m_systick_register_types)