Date: Fri, 26 May 2006 10:38:30 -0400
To: Robert Hancock <hancockr@shaw.ca>
Cc: Linas Vepstas <linas@austin.ibm.com>,
       linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: PCI reset using x86 or x86-64 BIOS calls?
Message-ID: <20060526143830.GA16442@csclub.uwaterloo.ca>
References: <6gr2t-1Pp-9@gated-at.bofh.it> <44765F57.90703@shaw.ca>
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From: lsorense@csclub.uwaterloo.ca (Lennart Sorensen)
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On Thu, May 25, 2006 at 07:52:23PM -0600, Robert Hancock wrote:
> Unlikely - if you mean just resetting one PCI device, it's likely 
> electrically impossible on many, if not most machines as the RST lines 
> will be tied together on all slots.
> 
> The BIOS might possibly have the ability to issue a PCI bus reset 
> independent of resetting the CPU, chipset, etc. but I don't think 
> there's any standardized way to trigger this, even so.
> 
> In any case, I don't think - or at least would hope - that a PCI device 
> going so far into the weeds that it can't be recovered without a RST 
> would be a rare situation.

Well I know there is a way to make a pci to pci bridge assert reset on
the secondary bus, which of course resets all devices behind the bridge.
I am not sure when, other than in the bios, this would be useful.  I
wouldn't want to have to go clean up the pci configuration settings on
all the devices after the reset.  I considered doing it to solve a rare
problem with some pci cards, but decided a reboot was simpler.

Len Sorensen
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