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

From: Yinghai Lu <yinghai@kernel.org>
To: Jiri Kosina <jkosina@suse.cz>
Cc: Harald Arnesen <skogtun.linux@gmail.com>,
	Kernel development list <linux-kernel@vger.kernel.org>,
	"Rafael J. Wysocki" <rjw@sisk.pl>,
	Peter Hurley <peter@hurleysoftware.com>,
	Alan Stern <stern@rowland.harvard.edu>,
	Thomas Meyer <thomas@m3y3r.de>,
	Shawn Starr <shawn.starr@rogers.com>,
	USB list <linux-usb@vger.kernel.org>,
	linux-acpi@vger.kernel.org, Bjorn Helgaas <bhelgaas@google.com>,
	linux-pci@vger.kernel.org, Daniel Vetter <daniel.vetter@ffwll.ch>,
	Imre Deak <imre.deak@intel.com>,
	Daniel Kurtz <djkurtz@chromium.org>,
	dri-devel@lists.freedesktop.org
Subject: Re: [3.9-rc1] irq 16: nobody cared (was [3.9-rc1] very poor interrupt responses)
Date: Mon, 18 Mar 2013 11:57:09 -0700	[thread overview]
Message-ID: <CAE9FiQXj0oD7_Abhz305dGytwg9_VKeEVuX128VXxEKexyvTLg@mail.gmail.com> (raw)
In-Reply-To: <alpine.LNX.2.00.1303181010080.9529@pobox.suse.cz>

On Mon, Mar 18, 2013 at 2:12 AM, Jiri Kosina <jkosina@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