linux-kernel - Re: [PATCH] s2io: add PCI error recovery support

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Date:	Wed, 25 Oct 2006 10:11:24 -0500
From:	linas@...tin.ibm.com (Linas Vepstas)
To:	Ananda Raju <Ananda.Raju@...erion.com>
Cc:	Wen Xiong <wenxiong@...ibm.com>, linux-kernel@...r.kernel.org,
	linux-pci@...ey.karlin.mff.cuni.cz, netdev@...r.kernel.org,
	Jeff Garzik <jgarzik@...ox.com>, Andrew Morton <akpm@...l.org>
Subject: Re: [PATCH] s2io: add PCI error recovery support

On Wed, Oct 25, 2006 at 02:29:33AM -0400, Ananda Raju wrote:
> Hi, 
> 
> s2io_card_down() will do few BAR0 read/write. As per
> pci-error-recovery.txt Documentation we are not supposed to do any new
> IO in error_detected(). 

Hmm, actually, its harmless to do further i/o. The s2io driver barks
(as it should) because the result of reads is always 0xffffffff.

> Can you try using 
> 
> atomic_set(&sp->card_state, CARD_DOWN); 
> 
> instead of s2io_card_down().

I will try that. I was mostly concerned that s2io_card_down()
also may do some other "important" things with regards to the driver
state, things which might be needed to keep the down-up sequence
symmetrical. I wasn't sure, so I took the conservative route.

> Also we have to add following if statement in beginning of s2io_isr().
> 
> if (atomic_read(&nic->card_state) == CARD_DOWN)
> 	return IRQ_NOTHANDLED.

Right! Will revise this patch shortly.

> If it is ok to do BAR0 read/write in error_detected() then patch is OK. 

Its OK on pSeries, and I beleive it will be OK on PCIE, but I do
not quite know enough about actual PCIE chipsets.

--linas

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