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Date: Mon, 23 Dec 2002 00:05:42 +0300
From: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
To: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>,
       Linus Torvalds <torvalds@transmeta.com>, davidm@hpl.hp.com,
       linux-kernel@vger.kernel.org
Subject: Re: PATCH 2.5.x disable BAR when sizing
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On Sun, Dec 22, 2002 at 12:47:51PM -0700, Eric W. Biederman wrote:
> Not if it is an NMI or an SCI interrupt.  The latter on x86 places
> the cpu in System Management Mode, and what the cpu does from that
> point forward is out of our control.
> 
> Though disabling cpu controlled IRQs help if you are dealing
> with any normal IRQs.

I meant the timer interrupt in the first place. I assumed it's the
only one that does matter on this stage of the boot process.
What else could happen (in the real world terms)?

> The window needs to be small from the PCI bus perspective, not in cpu
> clocks.  Write, Read, Write is only something like 9 PCI bus clocks.

No, the window is huge from the PCI bus perspective.
IIRC, PCI config read/write on x86 works like this (I may be wrong though):
i/o port write (BAR address)				~1us
i/o port read  (BAR value after writing ~0)		~1us
i/o port write (BAR address)				~1us
i/o port write (saved BAR value)			~1us

It's a little bit more than 9 PCI clocks. Am I missing something?

Ivan.
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