| From 8da854cb02156c90028233ae1e85ce46a1d3f82c Mon Sep 17 00:00:00 2001 |
| From: Pallipadi, Venkatesh <venkatesh.pallipadi@intel.com> |
| Date: Thu, 25 Feb 2010 10:53:48 -0800 |
| Subject: x86, hpet: Erratum workaround for read after write of HPET comparator |
| |
| From: Pallipadi, Venkatesh <venkatesh.pallipadi@intel.com> |
| |
| 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> |
| |
| --- |
| arch/x86/kernel/hpet.c | 8 +++++++- |
| 1 file changed, 7 insertions(+), 1 deletion(-) |
| |
| --- a/arch/x86/kernel/hpet.c |
| +++ b/arch/x86/kernel/hpet.c |
| @@ -398,9 +398,15 @@ static int hpet_next_event(unsigned long |
| * 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((u32)hpet_readl(HPET_Tn_CMP(timer)) != cnt, |
| + if (unlikely((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; |
| } |