diff options
| author | Pallipadi, Venkatesh <venkatesh.pallipadi@intel.com> | 2010-02-25 10:53:48 -0800 |
|---|---|---|
| committer | H. Peter Anvin <hpa@zytor.com> | 2010-04-01 15:21:47 -0700 |
| commit | 8da854cb02156c90028233ae1e85ce46a1d3f82c (patch) | |
| tree | 57a6b35416c198e9e4a38ccf10af06d7546c7887 /arch/x86/kernel | |
| parent | aa235fc712f379d4194cff9217f07026c452c141 (diff) | |
x86, hpet: Erratum workaround for read after write of HPET comparator
On Wed, Feb 24, 2010 at 03:37:04PM -0800, Justin Piszcz wrote:
> Hello,
>
> Again, on the Intel DP55KG board:
>
> # uname -a
> Linux host 2.6.33 #1 SMP Wed Feb 24 18:31:00 EST 2010 x86_64 GNU/Linux
>
> [ 1.237600] ------------[ cut here ]------------
> [ 1.237890] WARNING: at arch/x86/kernel/hpet.c:404 hpet_next_event+0x70/0x80()
> [ 1.238221] Hardware name:
> [ 1.238504] hpet: compare register read back failed.
> [ 1.238793] Modules linked in:
> [ 1.239315] Pid: 0, comm: swapper Not tainted 2.6.33 #1
> [ 1.239605] Call Trace:
> [ 1.239886] <IRQ> [<ffffffff81056c13>] ? warn_slowpath_common+0x73/0xb0
> [ 1.240409] [<ffffffff81079608>] ? tick_dev_program_event+0x38/0xc0
> [ 1.240699] [<ffffffff81056cb0>] ? warn_slowpath_fmt+0x40/0x50
> [ 1.240992] [<ffffffff81079608>] ? tick_dev_program_event+0x38/0xc0
> [ 1.241281] [<ffffffff81041ad0>] ? hpet_next_event+0x70/0x80
> [ 1.241573] [<ffffffff81079608>] ? tick_dev_program_event+0x38/0xc0
> [ 1.241859] [<ffffffff81078e32>] ? tick_handle_oneshot_broadcast+0xe2/0x100
> [ 1.246533] [<ffffffff8102a67a>] ? timer_interrupt+0x1a/0x30
> [ 1.246826] [<ffffffff81085499>] ? handle_IRQ_event+0x39/0xd0
> [ 1.247118] [<ffffffff81087368>] ? handle_edge_irq+0xb8/0x160
> [ 1.247407] [<ffffffff81029f55>] ? handle_irq+0x15/0x20
> [ 1.247689] [<ffffffff810294a2>] ? do_IRQ+0x62/0xe0
> [ 1.247976] [<ffffffff8146be53>] ? ret_from_intr+0x0/0xa
> [ 1.248262] <EOI> [<ffffffff8102f277>] ? mwait_idle+0x57/0x80
> [ 1.248796] [<ffffffff8102645c>] ? cpu_idle+0x5c/0xb0
> [ 1.249080] ---[ end trace db7f668fb6fef4e1 ]---
>
> Is this something Intel has to fix or is it a bug in the kernel?
This is a chipset erratum.
Thomas: You mentioned we can retain this check only for known-buggy and
hpet debug kind of options. But here is the simple workaround patch for
this particular erratum.
Some chipsets have a erratum due to which read immediately following a
write of HPET comparator returns old comparator value instead of most
recently written value.
Erratum 15 in
"Intel I/O Controller Hub 9 (ICH9) Family Specification Update"
(http://www.intel.com/assets/pdf/specupdate/316973.pdf)
Workaround for the errata is to read the comparator twice if the first
one fails.
Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
LKML-Reference: <20100225185348.GA9674@linux-os.sc.intel.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Cc: Venkatesh Pallipadi <venkatesh.pallipadi@gmail.com>
Cc: <stable@kernel.org>
Diffstat (limited to 'arch/x86/kernel')
| -rw-r--r-- | arch/x86/kernel/hpet.c | 8 |
1 files changed, 7 insertions, 1 deletions
diff --git a/arch/x86/kernel/hpet.c b/arch/x86/kernel/hpet.c index ee4fa1bfcb33..3d422da92100 100644 --- a/arch/x86/kernel/hpet.c +++ b/arch/x86/kernel/hpet.c @@ -399,9 +399,15 @@ static int hpet_next_event(unsigned long delta, * 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. + * An erratum on some chipsets (ICH9,..), results in comparator read + * immediately following a write returning old value. Workaround + * for this is to read this value second time, when first + * read returns old value. */ - WARN_ONCE(hpet_readl(HPET_Tn_CMP(timer)) != cnt, + if (unlikely((u32)hpet_readl(HPET_Tn_CMP(timer)) != cnt)) { + WARN_ONCE(hpet_readl(HPET_Tn_CMP(timer)) != cnt, KERN_WARNING "hpet: compare register read back failed.\n"); + } return (s32)(hpet_readl(HPET_COUNTER) - cnt) >= 0 ? -ETIME : 0; } |