diff options
author | Thomas Gleixner <tglx@linutronix.de> | 2009-11-27 15:24:44 +0100 |
---|---|---|
committer | Greg Kroah-Hartman <gregkh@suse.de> | 2010-04-26 07:41:24 -0700 |
commit | 0584aa8dea3dab7f49ce949f61d7ec92b6b29e3e (patch) | |
tree | e8e52efd186ab9c9f844786dcf0dbd456d2347ab | |
parent | 342fcebe9ef1013a6b655875d2272c2078c6355e (diff) |
x86: hpet: Make WARN_ON understandable
commit 18ed61da985c57eea3fe8038b13fa2837c9b3c3f upstream.
Andrew complained rightly that the WARN_ON in hpet_next_event() is
confusing and the code comment not really helpful.
Change it to WARN_ONCE and print the reason in clear text. Change the
comment to explain what kind of hardware wreckage we deal with.
Pointed-out-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Venki Pallipadi <venkatesh.pallipadi@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
-rw-r--r-- | arch/x86/kernel/hpet.c | 19 |
1 files changed, 15 insertions, 4 deletions
diff --git a/arch/x86/kernel/hpet.c b/arch/x86/kernel/hpet.c index 58778736496..4dda49c68a3 100644 --- a/arch/x86/kernel/hpet.c +++ b/arch/x86/kernel/hpet.c @@ -385,11 +385,22 @@ static int hpet_next_event(unsigned long delta, hpet_writel(cnt, HPET_Tn_CMP(timer)); /* - * We need to read back the CMP register to make sure that - * what we wrote hit the chip before we compare it to the - * counter. + * We need to read back the CMP register on certain HPET + * implementations (ATI chipsets) which seem to delay the + * transfer of the compare register into the internal compare + * logic. With small deltas this might actually be too late as + * the counter could already be higher than the compare value + * 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. */ - WARN_ON_ONCE((u32)hpet_readl(HPET_Tn_CMP(timer)) != cnt); + WARN_ONCE((u32)hpet_readl(HPET_Tn_CMP(timer)) != cnt, + KERN_WARNING "hpet: compare register read back failed.\n"); return (s32)((u32)hpet_readl(HPET_COUNTER) - cnt) >= 0 ? -ETIME : 0; } |