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armv7m: Split systick out from NVIC
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The SysTick timer isn't really part of the NVIC proper;
we just modelled it that way back when we couldn't
easily have devices that only occupied a small chunk
of a memory region. Split it out into its own device.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Message-id: 1487604965-23220-10-git-send-email-peter.maydell@linaro.org
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
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pm215 committed Feb 28, 2017
1 parent 743eb70 commit ff68dac
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Showing 6 changed files with 318 additions and 133 deletions.
160 changes: 34 additions & 126 deletions hw/intc/armv7m_nvic.c
View file
Expand Up @@ -58,65 +58,6 @@ static const uint8_t nvic_id[] = {
0x00, 0xb0, 0x1b, 0x00, 0x0d, 0xe0, 0x05, 0xb1
};

/* 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(NVICState *s)
{
if (s->systick.control & SYSTICK_CLKSOURCE)
return system_clock_scale;
else
return 1000;
}

static void systick_reload(NVICState *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.
*/
if ((s->systick.control & SYSTICK_ENABLE) == 0) {
return;
}

if (reset)
s->systick.tick = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
s->systick.tick += (s->systick.reload + 1) * systick_scale(s);
timer_mod(s->systick.timer, s->systick.tick);
}

static void systick_timer_tick(void * opaque)
{
NVICState *s = (NVICState *)opaque;
s->systick.control |= SYSTICK_COUNTFLAG;
if (s->systick.control & SYSTICK_TICKINT) {
/* Trigger the interrupt. */
armv7m_nvic_set_pending(s, ARMV7M_EXCP_SYSTICK);
}
if (s->systick.reload == 0) {
s->systick.control &= ~SYSTICK_ENABLE;
} else {
systick_reload(s, 0);
}
}

static void systick_reset(NVICState *s)
{
s->systick.control = 0;
s->systick.reload = 0;
s->systick.tick = 0;
timer_del(s->systick.timer);
}

static int nvic_pending_prio(NVICState *s)
{
/* return the priority of the current pending interrupt,
Expand Down Expand Up @@ -462,30 +403,6 @@ static uint32_t nvic_readl(NVICState *s, uint32_t offset)
switch (offset) {
case 4: /* Interrupt Control Type. */
return ((s->num_irq - NVIC_FIRST_IRQ) / 32) - 1;
case 0x10: /* SysTick Control and Status. */
val = s->systick.control;
s->systick.control &= ~SYSTICK_COUNTFLAG;
return val;
case 0x14: /* SysTick Reload Value. */
return s->systick.reload;
case 0x18: /* SysTick Current Value. */
{
int64_t t;
if ((s->systick.control & SYSTICK_ENABLE) == 0)
return 0;
t = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
if (t >= s->systick.tick)
return 0;
val = ((s->systick.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->systick.reload)
val = 0;
return val;
}
case 0x1c: /* SysTick Calibration Value. */
return 10000;
case 0xd00: /* CPUID Base. */
return cpu->midr;
case 0xd04: /* Interrupt Control State. */
Expand Down Expand Up @@ -620,40 +537,8 @@ static uint32_t nvic_readl(NVICState *s, uint32_t offset)
static void nvic_writel(NVICState *s, uint32_t offset, uint32_t value)
{
ARMCPU *cpu = s->cpu;
uint32_t oldval;

switch (offset) {
case 0x10: /* SysTick Control and Status. */
oldval = s->systick.control;
s->systick.control &= 0xfffffff8;
s->systick.control |= value & 7;
if ((oldval ^ value) & SYSTICK_ENABLE) {
int64_t now = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
if (value & SYSTICK_ENABLE) {
if (s->systick.tick) {
s->systick.tick += now;
timer_mod(s->systick.timer, s->systick.tick);
} else {
systick_reload(s, 1);
}
} else {
timer_del(s->systick.timer);
s->systick.tick -= now;
if (s->systick.tick < 0)
s->systick.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 0x14: /* SysTick Reload Value. */
s->systick.reload = value;
break;
case 0x18: /* SysTick Current Value. Writes reload the timer. */
systick_reload(s, 1);
s->systick.control &= ~SYSTICK_COUNTFLAG;
break;
case 0xd04: /* Interrupt Control State. */
if (value & (1 << 31)) {
armv7m_nvic_set_pending(s, ARMV7M_EXCP_NMI);
Expand Down Expand Up @@ -952,16 +837,12 @@ static const VMStateDescription vmstate_VecInfo = {

static const VMStateDescription vmstate_nvic = {
.name = "armv7m_nvic",
.version_id = 3,
.minimum_version_id = 3,
.version_id = 4,
.minimum_version_id = 4,
.post_load = &nvic_post_load,
.fields = (VMStateField[]) {
VMSTATE_STRUCT_ARRAY(vectors, NVICState, NVIC_MAX_VECTORS, 1,
vmstate_VecInfo, VecInfo),
VMSTATE_UINT32(systick.control, NVICState),
VMSTATE_UINT32(systick.reload, NVICState),
VMSTATE_INT64(systick.tick, NVICState),
VMSTATE_TIMER_PTR(systick.timer, NVICState),
VMSTATE_UINT32(prigroup, NVICState),
VMSTATE_END_OF_LIST()
}
Expand Down Expand Up @@ -999,13 +880,26 @@ static void armv7m_nvic_reset(DeviceState *dev)

s->exception_prio = NVIC_NOEXC_PRIO;
s->vectpending = 0;
}

systick_reset(s);
static void nvic_systick_trigger(void *opaque, int n, int level)
{
NVICState *s = opaque;

if (level) {
/* SysTick just asked us to pend its exception.
* (This is different from an external interrupt line's
* behaviour.)
*/
armv7m_nvic_set_pending(s, ARMV7M_EXCP_SYSTICK);
}
}

static void armv7m_nvic_realize(DeviceState *dev, Error **errp)
{
NVICState *s = NVIC(dev);
SysBusDevice *systick_sbd;
Error *err = NULL;

s->cpu = ARM_CPU(qemu_get_cpu(0));
assert(s->cpu);
Expand All @@ -1020,10 +914,19 @@ static void armv7m_nvic_realize(DeviceState *dev, Error **errp)
/* include space for internal exception vectors */
s->num_irq += NVIC_FIRST_IRQ;

object_property_set_bool(OBJECT(&s->systick), true, "realized", &err);
if (err != NULL) {
error_propagate(errp, err);
return;
}
systick_sbd = SYS_BUS_DEVICE(&s->systick);
sysbus_connect_irq(systick_sbd, 0,
qdev_get_gpio_in_named(dev, "systick-trigger", 0));

/* The NVIC and System Control Space (SCS) starts at 0xe000e000
* and looks like this:
* 0x004 - ICTR
* 0x010 - 0x1c - systick
* 0x010 - 0xff - systick
* 0x100..0x7ec - NVIC
* 0x7f0..0xcff - Reserved
* 0xd00..0xd3c - SCS registers
Expand All @@ -1041,10 +944,11 @@ static void armv7m_nvic_realize(DeviceState *dev, Error **errp)
memory_region_init_io(&s->sysregmem, OBJECT(s), &nvic_sysreg_ops, s,
"nvic_sysregs", 0x1000);
memory_region_add_subregion(&s->container, 0, &s->sysregmem);
memory_region_add_subregion_overlap(&s->container, 0x10,
sysbus_mmio_get_region(systick_sbd, 0),
1);

sysbus_init_mmio(SYS_BUS_DEVICE(dev), &s->container);

s->systick.timer = timer_new_ns(QEMU_CLOCK_VIRTUAL, systick_timer_tick, s);
}

static void armv7m_nvic_instance_init(Object *obj)
Expand All @@ -1059,8 +963,12 @@ static void armv7m_nvic_instance_init(Object *obj)
NVICState *nvic = NVIC(obj);
SysBusDevice *sbd = SYS_BUS_DEVICE(obj);

object_initialize(&nvic->systick, sizeof(nvic->systick), TYPE_SYSTICK);
qdev_set_parent_bus(DEVICE(&nvic->systick), sysbus_get_default());

sysbus_init_irq(sbd, &nvic->excpout);
qdev_init_gpio_out_named(dev, &nvic->sysresetreq, "SYSRESETREQ", 1);
qdev_init_gpio_in_named(dev, nvic_systick_trigger, "systick-trigger", 1);
}

static void armv7m_nvic_class_init(ObjectClass *klass, void *data)
Expand Down
1 change: 1 addition & 0 deletions hw/timer/Makefile.objs
View file
@@ -1,5 +1,6 @@
common-obj-$(CONFIG_ARM_TIMER) += arm_timer.o
common-obj-$(CONFIG_ARM_MPTIMER) += arm_mptimer.o
common-obj-$(CONFIG_ARM_V7M) += armv7m_systick.o
common-obj-$(CONFIG_A9_GTIMER) += a9gtimer.o
common-obj-$(CONFIG_CADENCE) += cadence_ttc.o
common-obj-$(CONFIG_DS1338) += ds1338.o
Expand Down

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