[Mesa-dev] SandyBridge issue likely related to fast color clears using meta operations

[Emil Velikov]

Hi Samuel,

On 02/09/14 17:22, Samuel Iglesias Gonsálvez wrote:
> Adding Kristian in Cc.
> 
> Sam
> 
> On Tue, 2014-09-02 at 18:16 +0200, Samuel Iglesias Gonsálvez wrote:
>> Hello,
>>
>> Two weeks ago, Iago and myself sent a batch of patches that added
>> geometry shader support for SandyBridge [0].
>>
>> Recently, we rebased our patches against master [1] and found
>> that some things are not working properly any more. Particularly, we
>> have plenty of cases where we only get a black screen when using a
>> geometry shader, and in these cases it seems as if some outputs of the
>> geometry shader got "lost" by the time they become inputs in the
>> fragment shader (some input varyings in the fragment shader that come
>> from the outputs of the geometry seem to be zeroed). The values we
>> output in the geometry shader are correct though, since they are
>> correctly captured by transform feedback.
>>
>> A bisect shows that the commit that introduced this problem is
>> 2f28a0dc231 i965: Implement fast color clears using meta operations [2].
>>
Seemingly the commit caused some issues which should be fixed with the
following. AFAICS the patch has landed in master, but I'm not sure if your
work is based on top of it or not.

http://lists.freedesktop.org/archives/mesa-dev/2014-August/066917.html


Cheers,
Emil

>> Reverting this commit fixes the problem for us. The revert also fixes
>> piglit's bin/gl-3.2-layered-rendering-clear-color* tests in SandyBridge
>> [3].
>>
>> So the question is whether the commit mentioned above introduces a
>> regression that should be fixed somewhere or if our code needs to be
>> updated to adapt to changes introduced by that commit in some way.
>>
>> Best regards,
>>
>> Sam
>>
>> [0]
>> http://lists.freedesktop.org/archives/mesa-dev/2014-August/065692.html
>>
>> [1]
>> https://github.com/samuelig/mesa/tree/gs-support-snb-for-submission-02092014
>>
>> [2]
>> commit 2f28a0dc23165123cf1e8b5942acad37878edd8a
>> Author: Kristian Høgsberg <krh at bitplanet.net>
>> Date:   Mon Jul 7 16:44:58 2014 -0700
>>
>>     i965: Implement fast color clears using meta operations
>>     
>>     This patch uses the infrastructure put in place by previous patches
>>     to implement fast color clears and replicated color clears in terms 
>>     of meta operations.
>>     
>>     This works all the way back to gen7 where fast clear was introduced 
>>     and adds support for fast clear on gen8.  It replaces the blorp path
>>     completely and improves on a few cases.  Layered clears are now done
>>     using instanced rendering and multiple render-target clears use a
>>     MRT shader with rep16 writes.
>>     
>>     Signed-off-by: Kristian Høgsberg <krh at bitplanet.net>
>>     Acked-by: Kenneth Graunke <kenneth at whitecape.org>
>>
>> [3]
>> http://people.igalia.com/siglesias/mesa/all-gs-patches-v2/changes.html
>> _______________________________________________
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> 
> 
> 
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