[Bug 61477] [965g] batch corruption, clflush?

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=61477

--- Comment #15 from Chris Wilson <chris at chris-wilson.co.uk> ---
(In reply to comment #9)
> The only interesting thing I've find is the pattern of 0x0040a0c0 in the
> batch. It repeats with a stride divisible by 128 and hits every odd dword.
> Vertical light blue lines in a y-tiled picture? Unfortunately no active
> y-tiled bo we could blame this on.

Yup, but the repeating data is not pixel data, looks more like contents from a
stale batch. And I can easily convince myself that each time it is just once
cacheline worth of bad data.

(In reply to comment #14)
> Okay, I bisected xf86-video-intel (for the corruption of window borders),
> with the result:
> 
> ab01fd696e1137ddfb9a85ae68c15c05900f0e8e is the first bad commit
> commit ab01fd696e1137ddfb9a85ae68c15c05900f0e8e
> Author: Chris Wilson <chris at chris-wilson.co.uk>
> Date:   Sat Jan 12 09:17:03 2013 +0000
> 
>     sna: Experiment with a CPU mapping for certain fallbacks

That ties right in with the theory that coherency on 965g is hosed in certain
situations - as I already know snooping is broken and this could just a very
similar effect.

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