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/*
* This file is subject to the terms and conditions of the GNU General Public
* License. See the file "COPYING" in the main directory of this archive
* for more details.
*
* Copyright (C) 2007 MIPS Technologies, Inc.
* Copyright (C) 2007 Ralf Baechle <ralf@linux-mips.org>
*/
#include <linux/clockchips.h>
#include <linux/interrupt.h>
#include <linux/percpu.h>
#include <linux/smp.h>
#include <linux/irq.h>
#include <asm/time.h>
#include <asm/cevt-r4k.h>
static int mips_next_event(unsigned long delta,
struct clock_event_device *evt)
{
unsigned int cnt;
int res;
cnt = read_c0_count();
cnt += delta;
write_c0_compare(cnt);
res = ((int)(read_c0_count() - cnt) >= 0) ? -ETIME : 0;
return res;
}
void mips_set_clock_mode(enum clock_event_mode mode,
struct clock_event_device *evt)
{
/* Nothing to do ... */
}
DEFINE_PER_CPU(struct clock_event_device, mips_clockevent_device);
int cp0_timer_irq_installed;
/*
* Possibly handle a performance counter interrupt.
* Return true if the timer interrupt should not be checked
*/
static inline int handle_perf_irq(int r2)
{
/*
* The performance counter overflow interrupt may be shared with the
* timer interrupt (cp0_perfcount_irq < 0). If it is and a
* performance counter has overflowed (perf_irq() == IRQ_HANDLED)
* and we can't reliably determine if a counter interrupt has also
* happened (!r2) then don't check for a timer interrupt.
*/
return (cp0_perfcount_irq < 0) &&
perf_irq() == IRQ_HANDLED &&
!r2;
}
irqreturn_t c0_compare_interrupt(int irq, void *dev_id)
{
const int r2 = cpu_has_mips_r2_r6;
struct clock_event_device *cd;
int cpu = smp_processor_id();
/*
* Suckage alert:
* Before R2 of the architecture there was no way to see if a
* performance counter interrupt was pending, so we have to run
* the performance counter interrupt handler anyway.
*/
if (handle_perf_irq(r2))
return IRQ_HANDLED;
/*
* The same applies to performance counter interrupts. But with the
* above we now know that the reason we got here must be a timer
* interrupt. Being the paranoiacs we are we check anyway.
*/
if (!r2 || (read_c0_cause() & CAUSEF_TI)) {
/* Clear Count/Compare Interrupt */
write_c0_compare(read_c0_compare());
cd = &per_cpu(mips_clockevent_device, cpu);
cd->event_handler(cd);
return IRQ_HANDLED;
}
return IRQ_NONE;
}
struct irqaction c0_compare_irqaction = {
.handler = c0_compare_interrupt,
/*
* IRQF_SHARED: The timer interrupt may be shared with other interrupts
* such as perf counter and FDC interrupts.
*/
.flags = IRQF_PERCPU | IRQF_TIMER | IRQF_SHARED,
.name = "timer",
};
void mips_event_handler(struct clock_event_device *dev)
{
}
/*
* FIXME: This doesn't hold for the relocated E9000 compare interrupt.
*/
static int c0_compare_int_pending(void)
{
/* When cpu_has_mips_r2, this checks Cause.TI instead of Cause.IP7 */
return (read_c0_cause() >> cp0_compare_irq_shift) & (1ul << CAUSEB_IP);
}
/*
* Compare interrupt can be routed and latched outside the core,
* so wait up to worst case number of cycle counter ticks for timer interrupt
* changes to propagate to the cause register.
*/
#define COMPARE_INT_SEEN_TICKS 50
int c0_compare_int_usable(void)
{
unsigned int delta;
unsigned int cnt;
#ifdef CONFIG_KVM_GUEST
return 1;
#endif
/*
* IP7 already pending? Try to clear it by acking the timer.
*/
if (c0_compare_int_pending()) {
cnt = read_c0_count();
write_c0_compare(cnt);
back_to_back_c0_hazard();
while (read_c0_count() < (cnt + COMPARE_INT_SEEN_TICKS))
if (!c0_compare_int_pending())
break;
if (c0_compare_int_pending())
return 0;
}
for (delta = 0x10; delta <= 0x400000; delta <<= 1) {
cnt = read_c0_count();
cnt += delta;
write_c0_compare(cnt);
back_to_back_c0_hazard();
if ((int)(read_c0_count() - cnt) < 0)
break;
/* increase delta if the timer was already expired */
}
while ((int)(read_c0_count() - cnt) <= 0)
; /* Wait for expiry */
while (read_c0_count() < (cnt + COMPARE_INT_SEEN_TICKS))
if (c0_compare_int_pending())
break;
if (!c0_compare_int_pending())
return 0;
cnt = read_c0_count();
write_c0_compare(cnt);
back_to_back_c0_hazard();
while (read_c0_count() < (cnt + COMPARE_INT_SEEN_TICKS))
if (!c0_compare_int_pending())
break;
if (c0_compare_int_pending())
return 0;
/*
* Feels like a real count / compare timer.
*/
return 1;
}
int r4k_clockevent_init(void)
{
unsigned int cpu = smp_processor_id();
struct clock_event_device *cd;
unsigned int irq;
if (!cpu_has_counter || !mips_hpt_frequency)
return -ENXIO;
if (!c0_compare_int_usable())
return -ENXIO;
/*
* With vectored interrupts things are getting platform specific.
* get_c0_compare_int is a hook to allow a platform to return the
* interrupt number of it's liking.
*/
irq = MIPS_CPU_IRQ_BASE + cp0_compare_irq;
if (get_c0_compare_int)
irq = get_c0_compare_int();
cd = &per_cpu(mips_clockevent_device, cpu);
cd->name = "MIPS";
cd->features = CLOCK_EVT_FEAT_ONESHOT |
CLOCK_EVT_FEAT_C3STOP |
CLOCK_EVT_FEAT_PERCPU;
clockevent_set_clock(cd, mips_hpt_frequency);
/* Calculate the min / max delta */
cd->max_delta_ns = clockevent_delta2ns(0x7fffffff, cd);
cd->min_delta_ns = clockevent_delta2ns(0x300, cd);
cd->rating = 300;
cd->irq = irq;
cd->cpumask = cpumask_of(cpu);
cd->set_next_event = mips_next_event;
cd->set_mode = mips_set_clock_mode;
cd->event_handler = mips_event_handler;
clockevents_register_device(cd);
if (cp0_timer_irq_installed)
return 0;
cp0_timer_irq_installed = 1;
setup_irq(irq, &c0_compare_irqaction);
return 0;
}
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