From: Borislav Petkov <borislav.petkov@amd.com>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: LKML <linux-kernel@vger.kernel.org>, Ingo Molnar <mingo@elte.hu>,
"H. Peter Anvin" <hpa@zytor.com>, Nix <nix@esperi.org.uk>,
Artur Skawina <art.08.09@gmail.com>,
Damien Wyart <damien.wyart@free.fr>,
John Drescher <drescherjm@gmail.com>,
Venkatesh Pallipadi <venki@google.com>,
Arjan van de Ven <arjan@linux.intel.com>,
"Herrmann3, Andreas" <Andreas.Herrmann3@amd.com>,
Suresh Siddha <suresh.b.siddha@intel.com>
Subject: Re: [PATCH RFC] x86: hpet: Avoid the readback penalty
Date: Wed, 15 Sep 2010 16:40:34 +0200 [thread overview]
Message-ID: <20100915144034.GC968@aftab> (raw)
In-Reply-To: <alpine.LFD.2.00.1009151500060.2416@localhost6.localdomain6>
From: Thomas Gleixner <tglx@linutronix.de>
Date: Wed, Sep 15, 2010 at 09:11:57AM -0400
> On Tue, 14 Sep 2010, tip-bot for Thomas Gleixner wrote:
> > x86: hpet: Work around hardware stupidity
>
> After my brain recovered from yesterdays exposure with the x86 timer
> horror, I came up with a different solution for this problem, which
> avoids the readback of the compare register completely. It works
> nicely on my affected ATI system, but needs some exposure to the other
> machines.
Will run in on a couple of SBx00 machines I got here.
...
> If cmp is less than 8 HPET clock cycles, then we decide that the event
> has happened already and return -ETIME. That covers the above #1 and
> #2 problems which would cause a wait for HPET wraparound (~306
> seconds).
Make sense. I guess you're choosing a value of 8 just to be on the safe
side wrt to HPET clock cycles it takes to write the cmp register?
--
Regards/Gruss,
Boris.
Advanced Micro Devices GmbH
Einsteinring 24, 85609 Dornach
General Managers: Alberto Bozzo, Andrew Bowd
Registration: Dornach, Gemeinde Aschheim, Landkreis Muenchen
Registergericht Muenchen, HRB Nr. 43632
next prev parent reply other threads:[~2010-09-15 14:39 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <tip-54ff7e595d763d894104d421b103a89f7becf47c@git.kernel.org>
2010-09-14 23:36 ` [tip:x86/urgent] x86: hpet: Work around hardware stupidity Venkatesh Pallipadi
2010-09-15 13:11 ` [PATCH RFC] x86: hpet: Avoid the readback penalty Thomas Gleixner
2010-09-15 13:43 ` Anders Larsen
2010-09-15 13:54 ` John Drescher
[not found] ` <AANLkTikHfDUh3LdmyA5eMNACFPfi6pqGLFJiyzVm79X_@mail.gmail.com>
2010-09-16 4:45 ` Fwd: " John Drescher
2010-09-15 14:40 ` Borislav Petkov [this message]
2010-09-15 14:42 ` Thomas Gleixner
2010-09-16 12:28 ` Borislav Petkov
2010-09-16 20:04 ` Nix
2010-09-18 7:49 ` Damien Wyart
2010-09-18 9:41 ` Thomas Gleixner
2010-09-18 13:43 ` Nix
2010-09-18 10:13 ` [tip:x86/timers] x86: Hpet: Avoid the comparator " tip-bot for Thomas Gleixner
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