Messages in this thread Patch in this message | | | Date | Thu, 4 Feb 2010 20:11:12 +0100 | From | Andi Kleen <> | Subject | [PATCH] HPET: Drop WARN_ON for mismatch on HPET CMP readback |
| |
HPET: Drop WARN_ON for mismatch on HPET CMP readback
At least one Intel chipset seems to always return a constant value when reading back the HPET CMP register. This triggers the WARN_ON_ONCE on each boot.
In addition the WARN_ON was buggy: it has a side-effect and actually needed code could be optimized out if someone disabled CONFIG_BUG.
So far there's no indication that miscompare on reading points to actual problem.
So simply drop the WARN_ON_ONCE.
Based on discussions with Thomas Gleixner.
Signed-off-by: Andi Kleen <ak@linux.intel.com>
diff --git a/arch/x86/kernel/hpet.c b/arch/x86/kernel/hpet.c index ad80a1c..18cf7a6 100644 --- a/arch/x86/kernel/hpet.c +++ b/arch/x86/kernel/hpet.c @@ -394,14 +394,11 @@ static int hpet_next_event(unsigned long delta, * at that point and we would wait for the next hpet interrupt * forever. We found out that reading the CMP register back * forces the transfer so we can rely on the comparison with - * the counter register below. If the read back from the - * compare register does not match the value we programmed - * then we might have a real hardware problem. We can not do - * much about it here, but at least alert the user/admin with - * a prominent warning. + * the counter register below. + * But don't actually check the read-back value. Some Intel chipsets + * return always the same value. */ - WARN_ONCE(hpet_readl(HPET_Tn_CMP(timer)) != cnt, - KERN_WARNING "hpet: compare register read back failed.\n"); + (void)hpet_readl(HPET_Tn_CMP(timer); return (s32)(hpet_readl(HPET_COUNTER) - cnt) >= 0 ? -ETIME : 0; }
| |