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[MIPS] Probe for usability of cp0 compare interrupt.

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Some processors offer the option of using the interrupt on which
normally the count / compare interrupt would be signaled as a normal
interupt pin.  Previously this required some ugly hackery for each
system which is much easier done by a quick and simple probe.

Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
This commit is contained in:
Ralf Baechle 2007-10-16 23:20:48 +01:00
parent 60b0d65541
commit b0d4056dd6
1 changed files with 47 additions and 0 deletions
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47
arch/mips/kernel/time.c
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@ -391,6 +391,50 @@ static 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;
}
static int c0_compare_int_usable(void)
{
const unsigned int delta = 0x300000;
unsigned int cnt;
/*
* IP7 already pending? Try to clear it by acking the timer.
*/
if (c0_compare_int_pending()) {
write_c0_compare(read_c0_compare());
irq_disable_hazard();
if (c0_compare_int_pending())
return 0;
}
cnt = read_c0_count();
cnt += delta;
write_c0_compare(cnt);
while ((long)(read_c0_count() - cnt) <= 0)
; /* Wait for expiry */
if (!c0_compare_int_pending())
return 0;
write_c0_compare(read_c0_compare());
irq_disable_hazard();
if (c0_compare_int_pending())
return 0;
/*
* Feels like a real count / compare timer.
*/
return 1;
}
void __cpuinit mips_clockevent_init(void)
{
uint64_t mips_freq = mips_hpt_frequency;
@ -412,6 +456,9 @@ void __cpuinit mips_clockevent_init(void)
return;
#endif
if (!c0_compare_int_usable())
return;
cd = &per_cpu(mips_clockevent_device, cpu);
cd->name = "MIPS";