diff options
Diffstat (limited to 'hw/timer/armv7m_systick.c')
| -rw-r--r-- | hw/timer/armv7m_systick.c | 240 |
1 files changed, 240 insertions, 0 deletions
diff --git a/hw/timer/armv7m_systick.c b/hw/timer/armv7m_systick.c new file mode 100644 index 0000000000..df8d2804b3 --- /dev/null +++ b/hw/timer/armv7m_systick.c @@ -0,0 +1,240 @@ +/* + * 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 "qemu-common.h" +#include "hw/sysbus.h" +#include "qemu/timer.h" +#include "qemu/log.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_reload(SysTickState *s, int reset) +{ + /* The Cortex-M3 Devices Generic User Guide says that "When the + * ENABLE bit is set to 1, the counter loads the RELOAD value from the + * SYST RVR register and then counts down". So, we need to check the + * ENABLE bit before reloading the value. + */ + trace_systick_reload(); + + if ((s->control & SYSTICK_ENABLE) == 0) { + return; + } + + if (reset) { + s->tick = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL); + } + s->tick += (s->reload + 1) * systick_scale(s); + timer_mod(s->timer, s->tick); +} + +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 (s->reload == 0) { + s->control &= ~SYSTICK_ENABLE; + } else { + systick_reload(s, 0); + } +} + +static uint64_t systick_read(void *opaque, hwaddr addr, unsigned size) +{ + SysTickState *s = opaque; + uint32_t val; + + switch (addr) { + case 0x0: /* SysTick Control and Status. */ + val = s->control; + s->control &= ~SYSTICK_COUNTFLAG; + break; + case 0x4: /* SysTick Reload Value. */ + val = s->reload; + break; + case 0x8: /* SysTick Current Value. */ + { + int64_t t; + + if ((s->control & SYSTICK_ENABLE) == 0) { + val = 0; + break; + } + t = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL); + if (t >= s->tick) { + val = 0; + break; + } + val = ((s->tick - (t + 1)) / systick_scale(s)) + 1; + /* The interrupt in triggered when the timer reaches zero. + However the counter is not reloaded until the next clock + tick. This is a hack to return zero during the first tick. */ + if (val > s->reload) { + val = 0; + } + 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); + return val; +} + +static void systick_write(void *opaque, hwaddr addr, + uint64_t value, unsigned size) +{ + SysTickState *s = opaque; + + trace_systick_write(addr, value, size); + + switch (addr) { + case 0x0: /* SysTick Control and Status. */ + { + uint32_t oldval = s->control; + + s->control &= 0xfffffff8; + s->control |= value & 7; + if ((oldval ^ value) & SYSTICK_ENABLE) { + int64_t now = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL); + if (value & SYSTICK_ENABLE) { + if (s->tick) { + s->tick += now; + timer_mod(s->timer, s->tick); + } else { + systick_reload(s, 1); + } + } else { + timer_del(s->timer); + s->tick -= now; + if (s->tick < 0) { + s->tick = 0; + } + } + } else if ((oldval ^ value) & SYSTICK_CLKSOURCE) { + /* This is a hack. Force the timer to be reloaded + when the reference clock is changed. */ + systick_reload(s, 1); + } + break; + } + case 0x4: /* SysTick Reload Value. */ + s->reload = value; + break; + case 0x8: /* SysTick Current Value. Writes reload the timer. */ + systick_reload(s, 1); + s->control &= ~SYSTICK_COUNTFLAG; + break; + default: + qemu_log_mask(LOG_GUEST_ERROR, + "SysTick: Bad write offset 0x%" HWADDR_PRIx "\n", addr); + } +} + +static const MemoryRegionOps systick_ops = { + .read = systick_read, + .write = 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); + + s->control = 0; + s->reload = 0; + s->tick = 0; + timer_del(s->timer); +} + +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->timer = timer_new_ns(QEMU_CLOCK_VIRTUAL, systick_timer_tick, s); +} + +static const VMStateDescription vmstate_systick = { + .name = "armv7m_systick", + .version_id = 1, + .minimum_version_id = 1, + .fields = (VMStateField[]) { + VMSTATE_UINT32(control, SysTickState), + VMSTATE_UINT32(reload, SysTickState), + VMSTATE_INT64(tick, SysTickState), + VMSTATE_TIMER_PTR(timer, 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; +} + +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) |