linux-kernel - Re: ASM1083 PCIx-PCI bridge interrupts

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Date:	Thu, 2 Feb 2012 11:28:08 -0800
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Edward Donovan <edward.donovan@...ble.net>
Cc:	Chris Palmer <chris.palmer@...ox.com>,
	Robert Hancock <hancockrwd@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Len Brown <lenb@...nel.org>, ghost3k@...st3k.net,
	linux-kernel@...r.kernel.org, keve@....hu,
	bjorn.ottervik@...il.com, kaneda@...email.hu,
	jeroen.vandenkeybus@...il.com, clemens@...isch.de
Subject: Re: ASM1083 PCIx-PCI bridge interrupts - widespread problems

On Thu, Feb 2, 2012 at 11:20 AM, Edward Donovan
<edward.donovan@...ble.net> wrote:
>
> If we end up helpless with this chip, will we at least warn the user
> that it's known to be buggy?  I dont' know if there's a standard
> procedure when documenting bad hardware.

That's probably a good idea.

That said, the "switch to polled mode and then try to reenable every
100ms" approach sounds like a good idea regardless. The more robust we
can be, the better.

I realize that the people with *this* particular problem would
probably want to reenable them even more often than 100ms or so, but
that could lead to problems for people with seriously screaming
interrupts (which has definitely happened too), so we need to balance
those two issues out against each other.

And we'd probably need to limit the warning messages if we start
re-enabling it - so that people with constantly screaming interrupts
don't get a constant stream of 10 "nobody cared, disabling" messages
per second.

So I'd take a tested patch that looks sane for both the "warning: this
pcie-pci bridge is dodgy" and for the "try polling, then re-enable for
a while" approach.

                    Linus
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