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authorRalf Baechle <ralf@linux-mips.org>2007-11-21 16:39:44 +0000
committerRalf Baechle <ralf@linux-mips.org>2007-11-26 17:26:14 +0000
commit5aa85c9fc49a6ce44dc10a42e2011bbde9dc445a (patch)
tree14b8d1a014349568be39753f879c152e1e3f2b41 /arch/mips/kernel/cevt-r4k.c
parent0f67e90e1caea4a0a14d2c60102547bce29f7f08 (diff)
[MIPS] Handle R4000/R4400 mfc0 from count register.
The R4000 and R4400 have an errata where if the cp0 count register is read in the exact moment when it matches the compare register no interrupt will be generated. This bug may be triggered if the cp0 count register is being used as clocksource and the compare interrupt as clockevent. So a simple workaround is to avoid using the compare for both facilities on the affected CPUs. This is different from the workaround suggested in the old errata documents; at some opportunity probably the official version should be implemented and tested. Another thing to find out is which processor versions exactly are affected. I only have errata documents upto R4400 V3.0 available so for the moment the code treats all R4000 and R4400 as broken. This is potencially a problem for some machines that have no other decent clocksource available; this workaround will cause them to fall back to another clocksource, worst case the "jiffies" source.
Diffstat (limited to 'arch/mips/kernel/cevt-r4k.c')
-rw-r--r--arch/mips/kernel/cevt-r4k.c12
1 files changed, 7 insertions, 5 deletions
diff --git a/arch/mips/kernel/cevt-r4k.c b/arch/mips/kernel/cevt-r4k.c
index 076f52b9bb79..24a2d907aa0d 100644
--- a/arch/mips/kernel/cevt-r4k.c
+++ b/arch/mips/kernel/cevt-r4k.c
@@ -219,7 +219,7 @@ static int c0_compare_int_usable(void)
return 1;
}
-void __cpuinit mips_clockevent_init(void)
+int __cpuinit mips_clockevent_init(void)
{
uint64_t mips_freq = mips_hpt_frequency;
unsigned int cpu = smp_processor_id();
@@ -227,7 +227,7 @@ void __cpuinit mips_clockevent_init(void)
unsigned int irq;
if (!cpu_has_counter || !mips_hpt_frequency)
- return;
+ return -ENXIO;
#ifdef CONFIG_MIPS_MT_SMTC
setup_smtc_dummy_clockevent_device();
@@ -237,11 +237,11 @@ void __cpuinit mips_clockevent_init(void)
* device.
*/
if (cpu)
- return;
+ return 0;
#endif
if (!c0_compare_int_usable())
- return;
+ return -ENXIO;
/*
* With vectored interrupts things are getting platform specific.
@@ -277,7 +277,7 @@ void __cpuinit mips_clockevent_init(void)
clockevents_register_device(cd);
if (cp0_timer_irq_installed)
- return;
+ return 0;
cp0_timer_irq_installed = 1;
@@ -287,4 +287,6 @@ void __cpuinit mips_clockevent_init(void)
#else
setup_irq(irq, &c0_compare_irqaction);
#endif
+
+ return 0;
}