[3.9-rc1] irq 16: nobody cared (was [3.9-rc1] very poor interrupt responses)

[Yinghai Lu]

On Mon, Mar 18, 2013 at 2:12 AM, Jiri Kosina <jkosina at suse.cz> wrote:
> On Fri, 15 Mar 2013, Yinghai Lu wrote:
>
>> > Just a datapoint -- I have put a trivial debugging patch in place, and it
>> > reveals that "nobody cared" for irq 16 happens long after last
>> >
>> >         I915_WRITE(GMBUS4 + reg_offset, 0);
>> >
>> > has been performed in gmbus_wait_hw_status(). On the other hand, if I
>> > comment out both GMBUS4 register offset writes in gmbus_wait_hw_status(),
>> > then it of course falls back to GPIO bit-banging, but the "nobody cared"
>> > for irq 16 is gone.
>> >
>> > So it seems like something gets severely confused by the I915_WRITE to
>> > GMBUS4 + reg_offset. So far this seems to have been reported solely on
>> > Lenovos as far as I can see (although a completely different types), so it
>> > might be some platform-specific quirk?
>> >
>> > Honestly, I still don't understand how all the GMBUS stuff relates to IRQ
>> > 16 at all.
>>
>> that device is using
>> i915 0000:00:02.0: irq 44 for MSI/MSI-X
>>
>> so can you try to boot with pci=nomsi?
>
> Yes, switching from MSI to IO-APIC-fasteoi makes the report about lost
> interrupts go away.
>
> My understanding from the other mail is that DAniel Vetter already has an
> idea what might be going wrong with IRQ acking on GM45 chipsets; hopefully
> this datapoint regarding MSI will fit into it.

What is /proc/interrupts difference between with and without pci=nomsi ?

drm is forced to share irq 16?

Thanks

Yinghai