kernel-fxtec-pro1x/arch/mips/kernel/cevt-r4k.c
Kevin D. Kissell 8531a35e5e [MIPS] SMTC: Fix SMTC dyntick support.
Rework of SMTC support to make it work with the new clock event system,
allowing "tickless" operation, and to make it compatible with the use of
the "wait_irqoff" idle loop.  The new clocking scheme means that the
previously optional IPI instant replay mechanism is now required, and has
been made more robust.

Signed-off-by: Kevin D. Kissell <kevink@paralogos.com>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
2008-10-03 17:58:58 +01:00

215 lines
5 KiB
C

/*
* 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 <asm/smtc_ipi.h>
#include <asm/time.h>
#include <asm/cevt-r4k.h>
/*
* The SMTC Kernel for the 34K, 1004K, et. al. replaces several
* of these routines with SMTC-specific variants.
*/
#ifndef CONFIG_MIPS_MT_SMTC
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;
}
#endif /* CONFIG_MIPS_MT_SMTC */
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;
#ifndef CONFIG_MIPS_MT_SMTC
irqreturn_t c0_compare_interrupt(int irq, void *dev_id)
{
const int r2 = cpu_has_mips_r2;
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))
goto out;
/*
* 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() & (1 << 30))) {
/* Clear Count/Compare Interrupt */
write_c0_compare(read_c0_compare());
cd = &per_cpu(mips_clockevent_device, cpu);
cd->event_handler(cd);
}
out:
return IRQ_HANDLED;
}
#endif /* Not CONFIG_MIPS_MT_SMTC */
struct irqaction c0_compare_irqaction = {
.handler = c0_compare_interrupt,
.flags = IRQF_DISABLED | IRQF_PERCPU,
.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)
{
return (read_c0_cause() >> cp0_compare_irq) & 0x100;
}
/*
* Compare interrupt can be routed and latched outside the core,
* so a single execution hazard barrier may not be enough to give
* it time to clear as seen in the Cause register. 4 time the
* pipeline depth seems reasonably conservative, and empirically
* works better in configurations with high CPU/bus clock ratios.
*/
#define compare_change_hazard() \
do { \
irq_disable_hazard(); \
irq_disable_hazard(); \
irq_disable_hazard(); \
irq_disable_hazard(); \
} while (0)
int c0_compare_int_usable(void)
{
unsigned int delta;
unsigned int cnt;
/*
* IP7 already pending? Try to clear it by acking the timer.
*/
if (c0_compare_int_pending()) {
write_c0_compare(read_c0_count());
compare_change_hazard();
if (c0_compare_int_pending())
return 0;
}
for (delta = 0x10; delta <= 0x400000; delta <<= 1) {
cnt = read_c0_count();
cnt += delta;
write_c0_compare(cnt);
compare_change_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 */
compare_change_hazard();
if (!c0_compare_int_pending())
return 0;
write_c0_compare(read_c0_count());
compare_change_hazard();
if (c0_compare_int_pending())
return 0;
/*
* Feels like a real count / compare timer.
*/
return 1;
}
#ifndef CONFIG_MIPS_MT_SMTC
int __cpuinit mips_clockevent_init(void)
{
uint64_t mips_freq = mips_hpt_frequency;
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;
/* Calculate the min / max delta */
cd->mult = div_sc((unsigned long) mips_freq, NSEC_PER_SEC, 32);
cd->shift = 32;
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(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;
}
#endif /* Not CONFIG_MIPS_MT_SMTC */