Date:	Wed, 06 Mar 2013 10:37:03 +0200
From:	Jani Nikula <jani.nikula@...ux.intel.com>
To:	Daniel Vetter <daniel.vetter@...ll.ch>,
	Benson Leung <bleung@...omium.org>
Cc:	intel-gfx <intel-gfx@...ts.freedesktop.org>,
	"linux-kernel\@vger.kernel.org" <linux-kernel@...r.kernel.org>,
	dri-devel@...ts.freedesktop.org,
	Olof Johansson <olofj@...omium.org>,
	Yufeng Shen <miletus@...omium.org>
Subject: Re: v3.9-rc1 instability on Chromebook Pixel with gmbus irq

On Wed, 06 Mar 2013, Daniel Vetter <daniel.vetter@...ll.ch> wrote:
> On Wed, Mar 6, 2013 at 3:35 AM, Benson Leung <bleung@...omium.org> wrote:
>> I'm working on touch devices Chromium OS, and I've noticed a
>> regression between 3.8 and 3.9-rc1, which was posted yesterday.
>>
>> The hardware in question is a Chromebook Pixel. For this device, we
>> have i2c input devices: atmel mxt224s touchpad and atmel mxt1664s
>> touchscreen. The touchpad is on bus 1, "i915 gmbus vga" at 1-004b. The
>> touchscreen is on bus 2, "i915 gmbus panel" at 2-004a.
>>
>> I was testing v3.9-rc1 on the Pixel and the touchscreen driver is
>> being returned -110 (-ETIMEDOUT) on an i2c_transfer after several
>> seconds of both touch devices working correctly. At the time of the
>> failure, there are no error messages from GMBUS that I can see, but
>> the bus never recovers. I can keep interacting with the touchscreen or
>> touchpad, and the interrupts trigger reads, but all subsequent reads
>> return -110.
>>
>> I noticed that between 3.8 and 3.9-rc1, your patch series to add gmbus
>> irq support was merged. After bisecting, I found that this commit
>> seems to be causing the timeout problem. Reverting it makes the
>> problem go away, and the bus is stable.
>
> Can you please retest with latest drm-intel-fixes merged into -rc1?
> Paulo's patch fixes a race in handling PCH interrupts (where the gmbus
> hw is) which matches rather well with your description here.

Also, some error paths only print with debug on. Did you try with
drm.debug=0xe?

BR,
Jani.


>
> Thanks, Daniel
>
>> commit 2c438c0273b76d6cb158f8bdd0aa3ebf66e48a28
>> Author: Daniel Vetter <daniel.vetter@...ll.ch>
>> Date:   Sat Dec 1 13:53:46 2012 +0100
>>
>>     drm/i915: use gmbus irq to wait for gmbus idle
>>
>>     GMBUS_ACTIVE has inverted sense and so doesn't fit into the
>>     wait_hw_status helper, hence create a new gmbus_wait_idle functions.
>>     Also, we only care about the idle irq event and nothing else, which
>>     allows us to use the wait_event_timeout helper directly without
>>     jumping through hoops to catch NAKs.
>>
>>     Since gen2/3 don't have gmbus interrupts, handle them separately with
>>     the old wait_for macro.
>>
>>     This shaves another few ms off reading EDID from a hdmi screen on my
>>     testbox here. EDID reading with interrupt driven gmbus is now as fast
>>     as with busy-looping gmbus at 28 ms here (with negligible cpu
>>     overhead).
>>
>>     Reviewed-by: Imre Deak <imre.deak@...el.com>
>>     Signed-off-by: Daniel Vetter <daniel.vetter@...ll.ch>
>>
>>
>> Is there anything I can do to help debug this some more?
>>
>> --
>> Benson Leung
>> Software Engineer, Chrom* OS
>> bleung@...omium.org
>
>
>
> -- 
> Daniel Vetter
> Software Engineer, Intel Corporation
> +41 (0) 79 365 57 48 - http://blog.ffwll.ch
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> dri-devel@...ts.freedesktop.org
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