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Date: Thu, 25 Feb 2010 21:38:31 +0100 (CET)
From: Thomas Gleixner <tglx@linutronix.de>
To: "Pallipadi, Venkatesh" <venkatesh.pallipadi@intel.com>
cc: Justin Piszcz <jpiszcz@lucidpixels.com>,
       "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: 2.6.33: Problem continues: WARNING: at arch/x86/kernel/hpet.c:404
 hpet_next_event+0x70/0x80
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On Thu, 25 Feb 2010, Pallipadi, Venkatesh wrote:

> 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.

Yes, that'd be the preferred way. I need to find the box which had the
problem (ATI chipset) and force the readback for that one. That saves
all other machines the extra hardware access.

Thanks,

	tglx
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