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authorPallipadi, Venkatesh <venkatesh.pallipadi@intel.com>2010-02-25 13:53:48 -0500
committerGreg Kroah-Hartman <gregkh@suse.de>2010-04-26 10:47:53 -0400
commit9f03442b0fcd587afd232ce8386114a5290e9f8f (patch)
tree475371a12cf521e70d8b97246f6f9f075b454e29 /arch/x86/kernel
parent16f886e00b3d52dca4b4d4a7e8ceaeaef7bb2b6c (diff)
x86, hpet: Erratum workaround for read after write of HPET comparator
commit 8da854cb02156c90028233ae1e85ce46a1d3f82c upstream. 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> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Diffstat (limited to 'arch/x86/kernel')
-rw-r--r--arch/x86/kernel/hpet.c8
1 files changed, 7 insertions, 1 deletions
diff --git a/arch/x86/kernel/hpet.c b/arch/x86/kernel/hpet.c
index ad80a1c718c6..773afc9274a1 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,
399 * then we might have a real hardware problem. We can not do 399 * then we might have a real hardware problem. We can not do
400 * much about it here, but at least alert the user/admin with 400 * much about it here, but at least alert the user/admin with
401 * a prominent warning. 401 * a prominent warning.
402 * An erratum on some chipsets (ICH9,..), results in comparator read
403 * immediately following a write returning old value. Workaround
404 * for this is to read this value second time, when first
405 * read returns old value.
402 */ 406 */
403 WARN_ONCE(hpet_readl(HPET_Tn_CMP(timer)) != cnt, 407 if (unlikely((u32)hpet_readl(HPET_Tn_CMP(timer)) != cnt)) {
408 WARN_ONCE(hpet_readl(HPET_Tn_CMP(timer)) != cnt,
404 KERN_WARNING "hpet: compare register read back failed.\n"); 409 KERN_WARNING "hpet: compare register read back failed.\n");
410 }
405 411
406 return (s32)(hpet_readl(HPET_COUNTER) - cnt) >= 0 ? -ETIME : 0; 412 return (s32)(hpet_readl(HPET_COUNTER) - cnt) >= 0 ? -ETIME : 0;
407} 413}