Re: ASM1083 PCIx-PCI bridge interrupts - widespread problems

[Chris Palmer <chris.palmer@pobox.com>]

On 31/01/2012 02:12, Robert Hancock wrote:
> On 01/30/2012 09:04 AM, Chris Palmer wrote:
>> Linus et al
>>
>>
>> For about 6 months many users have been having interrupt problems
>> with PCI boards, but it hasn't been
>> easy trying to find where the problem may be. However, it is now
>> looking likely that the problem lies
>> in the ASM1083 PCIe-PCI bridge chipset, as used by Asus in many
>> Sandybridge and AMD boards.
>>
>> My original bug report is:
>>      https://bugzilla.kernel.org/show_bug.cgi?id=38632  (Sandybridge)
>>
>> and there several other similar ones. However there is also extensive
>> investigation in the following thread:
>>      http://www.gossamer-threads.com/lists/linux/kernel/1466185  (AMD)
>>
>> There have also been reports of Windows users having similar problems.
>>
>> This problem prevents use of PCI boards in any motherboard with that
>> bridge chipset - including most
>> ASUS boards. At the moment though we don't know whether the chipset
>> or drivers are faulty, and if a
>> workaround is possible.
>>
>> At the moment my bug is assigned to drivers_network, but this doesn't
>> look appropriate.
>>
>> Hoping someone can help...
>
> If the analysis posted in the "Unhandled IRQs on AMD E-450" thread is
> correct, then it sounds like the bridge chip is delaying PCIe INTx
> deassert messages. In that case there isn't much the kernel is likely
> to be able to fix it properly, at least not without input from ASMedia
> or someone else with detailed knowledge of the chip.
>
> The workaround posted in that thread (switching to IRQ polling mode on
> the interrupt for some period of time after a screaming IRQ is
> detected) might be a workaround, but definitely would be considered a
> hack.
>
> Do you have a source/link for people having issues with this on
> Windows? I wouldn't be surprised though - I doubt Windows has any
> special handling for unhandled IRQs so likely it just hammers the IRQ
> handler until the IRQ gets deasserted. In that case the only thing a
> user might notice would be poor performance whenever the devices
> behind that bridge raise interrupts.
>

Nothing definitive about Windows, but Edward found this discussion. It's
a bit emotive, but suggests the problem may be manifesting itself there too:

http://forums.planetz.com/viewtopic.php?f=19&t=30557&sid=00d319732500eaf99c586b73060a9602

Chris

>>
>>
>>
>>
>> On 09/09/2011 00:51, Andrew Morton wrote:
>>
>>> On Thu, 08 Sep 2011 12:28:40 +0100
>>> Chris Palmer<chris.palmer@pobox.com>  wrote:
>>>
>>>> Andrew
>>>>
>>>> I'm writing to ask if you could cast a quick eye over the following
>>>> bugs, to give an opinion on where they should be assigned. Mine has
>>>> been
>>>> reassigned to Network Drivers but I'm not convinced that is right,
>>>> and I
>>>> think the problem is wider than that.
>>>>
>>>> In summary, interrupt handling for *PCI boards with ASUS Sandybridge
>>>> motherboards* seems to be broken.
>>>>
>>>> It has been seen with network and non-network PCI boards. PCIx network
>>>> boards work OK. And all reports are for ASUS motherboards.
>>>>
>>>> My bug report is
>>>>
>>>> https://bugzilla.kernel.org/show_bug.cgi?id=38632
>>>>
>>>> Others that I know of are:
>>>>
>>>> https://bugzilla.redhat.com/show_bug.cgi?id=713351
>>>> https://bugzilla.kernel.org/show_bug.cgi?id=35332
>>>> https://bugzilla.kernel.org/show_bug.cgi?id=34242
>>>> https://bugzilla.kernel.org/show_bug.cgi?id=32242
>>>> https://bugzilla.kernel.org/show_bug.cgi?id=39122
>>>>
>>>>
>>>> I'm now on kernel 3.0.4 with the problem still there. The only thing
>>>> that seems to make a difference is acpi=off (although one person
>>>> reported that it merely changed it from minutes to days before
>>>> occurring).
>>>>
>>>> I'd appreciate anything you could do to move this in the right
>>>> direction...
>>>>
>>>
>>> Most likely ACPI, I expect.  I think that's
>>> acpi-config-interrupts@bugzilla.kernel.org.  kernel.org DNS is dead at
>>> present and I can't check.
>>>
>>> Len, can you suggest how to triage these please?
>