linux-kernel - Re: [BUG] drm/i915 Screen corruption introduced by a00b10c360b35d6431a94cb

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Date:	Sat, 19 Feb 2011 19:25:11 +0100
From:	Daniel Vetter <daniel@...ll.ch>
To:	Indan Zupancic <indan@....nu>
Cc:	Chris Wilson <chris@...is-wilson.co.uk>,
	Daniel Vetter <daniel.vetter@...ll.ch>,
	LKML <linux-kernel@...r.kernel.org>,
	dri-devel@...ts.freedesktop.org
Subject: Re: [BUG] drm/i915 Screen corruption introduced by
 a00b10c360b35d6431a94cb

Hi Indan,

Please provide the usual details about your system (especially what gpu
this is on). Also, screenshots of what typical corruptions look like can
help a lot in tracking down such things.

I've created two quick patches to check a few theories, please test them
(both patches independently and both together). Patches attached.

Yours, Daniel

On Sat, Feb 19, 2011 at 06:58:06AM +0100, Indan Zupancic wrote:
> Hello,
> 
> Since 2.6.38-rc I get screen corruption (mostly horizontal grabage stripes on
> the right side of the screen). After a long time bisecting the offending commit
> ends up being:
> 
> commit a00b10c360b35d6431a94cbf130a4e162870d661
> Author: Chris Wilson <chris@...is-wilson.co.uk>
> Date:   Fri Sep 24 21:15:47 2010 +0100
> 
>     drm/i915: Only enforce fence limits inside the GTT.
> 
>     So long as we adhere to the fence registers rules for alignment and no
>     overlaps (including with unfenced accesses to linear memory) and account
>     for the tiled access in our size allocation, we do not have to allocate
>     the full fenced region for the object. This allows us to fight the bloat
>     tiling imposed on pre-i965 chipsets and frees up RAM for real use. [Inside
>     the GTT we still suffer the additional alignment constraints, so it doesn't
>     magic allow us to render larger scenes without stalls -- we need the
>     expanded GTT and fence pipelining to overcome those...]
> 
>     Signed-off-by: Chris Wilson <chris@...is-wilson.co.uk>
> 
> This commit caused other problems too, which Daniel tried to fix with commits:
> 
> 5e78330126e23e00950 drm/i915: fix relaxed tiling for gen <= 3 && !g33
> 75e9e9158f38e5cb21e drm/i915: kill mappable/fenceable disdinction
> 818f2a3cc34b0673dcc drm/i915: revert pageflip/mappable related abi breakage
> 
> But those don't fix my screen corruption.
> 
> Unfortunately, it's a big commit and it doesn't revert cleanly, and its size
> makes it unclear what the source of the problem is. Daniel's commits don't
> revert cleanly either, so reverting all of them didn't work.
> 
> I'll start poking at it and see if I can find anything.
> 
> Greetings,
> 
> Indan
> 
> 

-- 
Daniel Vetter
Mail: daniel@...ll.ch
Mobile: +41 (0)79 365 57 48

View attachment "for-indan-1.patch" of type "text/x-diff" (452 bytes)

View attachment "for-indan-2.patch" of type "text/x-diff" (431 bytes)