linux/arch
Pallipadi, Venkatesh 8da854cb02 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>
2010-04-01 15:21:47 -07:00
..
alpha alpha: fix compile errors in dma-mapping-common.h 2010-03-18 22:35:28 -04:00
arm [ARM] Orion5x: replace KEY_WLAN with KEY_WPS_BUTTON 2010-03-23 13:48:15 -04:00
avr32 avr32: use generic ptrace_resume code 2010-03-12 15:52:38 -08:00
blackfin Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/vapier/blackfin 2010-03-18 17:02:35 -07:00
cris Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial 2010-03-12 16:04:50 -08:00
frv frv/PCI: remove redundant warnings 2010-03-25 08:51:40 -07:00
h8300 Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial 2010-03-12 16:04:50 -08:00
ia64 ACPI: processor: driver doesn't need to evaluate _PDC 2010-03-14 21:17:22 -04:00
m32r m32r: use generic ptrace_resume code 2010-03-12 15:52:39 -08:00
m68k Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial 2010-03-12 16:04:50 -08:00
m68knommu m68knommu: use generic ptrace_resume code 2010-03-12 15:52:38 -08:00
microblaze Merge branch 'for-linus' of git://git.monstr.eu/linux-2.6-microblaze 2010-03-18 16:57:24 -07:00
mips init dynamic bin_attribute structures 2010-03-14 20:28:39 -07:00
mn10300 dma-mapping: mn10300: remove the obsolete and unnecessary DMA API comments 2010-03-12 15:52:42 -08:00
parisc pci-dma: add linux/pci-dma.h to linux/pci.h 2010-03-12 15:52:42 -08:00
powerpc Merge branch 'perf-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip 2010-03-26 15:09:33 -07:00
s390 [S390] fix boot failures with compressed kernels 2010-03-24 11:49:54 +01:00
score ptrace: move user_enable_single_step & co prototypes to linux/ptrace.h 2010-03-12 15:52:38 -08:00
sh sh: Silence unintialized variable warnings in dwarf unwinder. 2010-03-23 17:07:41 +09:00
sparc Merge branch 'perf-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip 2010-03-13 14:39:42 -08:00
um um: remove dma_sync_single_range 2010-03-12 15:52:40 -08:00
x86 x86, hpet: Erratum workaround for read after write of HPET comparator 2010-04-01 15:21:47 -07:00
xtensa Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial 2010-03-12 16:04:50 -08:00
.gitignore
Kconfig Merge branch 'perf-probes-for-linus-2' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip 2010-03-05 10:50:22 -08:00