The 'mult' element of struct clock_event_device must never be wider
than 32-bits. If it were, it would get truncated when used by
clockevent_delta2ns() when this calls do_div().
We meet the requirement by ensuring that the relationship:
(mips_hpt_frequency >> (32 - shift)) < NSEC_PER_SEC
Always holds.
Signed-off-by: David Daney <ddaney@xxxxxxxxxxxxxxxxxx>
CC: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
---
arch/mips/kernel/cevt-r4k.c | 16 +++++++++++++---
1 files changed, 13 insertions(+), 3 deletions(-)
diff --git a/arch/mips/kernel/cevt-r4k.c b/arch/mips/kernel/cevt-r4k.c
index 0b2450c..4495158 100644
--- a/arch/mips/kernel/cevt-r4k.c
+++ b/arch/mips/kernel/cevt-r4k.c
@@ -163,10 +163,11 @@ int c0_compare_int_usable(void)
int __cpuinit r4k_clockevent_init(void)
{
- uint64_t mips_freq = mips_hpt_frequency;
+ uint64_t scaled_freq = mips_hpt_frequency;
unsigned int cpu = smp_processor_id();
struct clock_event_device *cd;
unsigned int irq;
+ int shift;
if (!cpu_has_counter || !mips_hpt_frequency)
return -ENXIO;
@@ -189,8 +190,17 @@ int __cpuinit r4k_clockevent_init(void)
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;
+ shift = 32;
+ while (scaled_freq >= NSEC_PER_SEC && shift) {
+ scaled_freq = scaled_freq >> 1;
+ shift--;
+ }
+ BUG_ON(shift == 0);
+
+ cd->mult = div_sc((unsigned long) mips_hpt_frequency,
+ NSEC_PER_SEC, shift);
+ cd->shift = shift;
+
cd->max_delta_ns = clockevent_delta2ns(0x7fffffff, cd);
cd->min_delta_ns = clockevent_delta2ns(0x300, cd);
--
1.6.6.1
