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Date: Mon, 18 Mar 2013 08:14:48 +0100
Subject: Re: [3.9-rc1] irq 16: nobody cared  (was [3.9-rc1] very poor
 interrupt responses)
Message-ID: <3mh5gd58po5ybltccyfh2htu.1363590888245@email.android.com>
From: Thomas Meyer <thomas@m3y3r.de>
To: Jiri Kosina <jkosina@suse.cz>
Cc: Harald Arnesen <skogtun.linux@gmail.com>,
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        Daniel Vetter <daniel.vetter@ffwll.ch>,
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My laptop is an Acer 1810T. I see this error message each boot.

Kind regards
Thomas

Jiri Kosina <jkosina@suse.cz> schrieb:

>On Fri, 15 Mar 2013, Jiri Kosina wrote:
>
>> > I have the same problem on my Lenovo T500. I think the graphics card is
>> > involved.
>> > 
>> > This laptop has "hybrid graphics" - one Intel GMA 4500MHD and one ATI
>> > Mobility Radeon HD 3650. When I boot with the Intel card, I get "irq 16:
>> > nobody cared" during boot, not when I boot with the ATI card.
>> 
>> Confirming this. After a lot of hassle, I have bisected this reliably to
>> 
>> 	commit 28c70f162a315bdcfbe0bf940a740ef8bfb918d6
>> 	Author: Daniel Vetter <daniel.vetter@ffwll.ch>
>> 	Date:   Sat Dec 1 13:53:45 2012 +0100
>> 
>> 	    drm/i915: use the gmbus irq for waits
>> 
>> Adding Daniel, Imre and Daniel to CC while I will try to figure out what's 
>> happening in parallel.
>> 
>> Attaching dmesg.txt from the machine with 28c70f162a as head, with 
>> drm.debug=0xe.
>
>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. 
>
>-- 
>Jiri Kosina
>SUSE Labs
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