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Date:   Fri, 20 Nov 2020 14:41:42 +0100
From:   Thomas Zimmermann <tzimmermann@...e.de>
To:     David Laight <David.Laight@...LAB.COM>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Daniel Vetter <daniel.vetter@...ll.ch>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        "Huang, Ray" <ray.huang@....com>, Dave Airlie <airlied@...hat.com>,
        Christian König <christian.koenig@....com>
Subject: Re: Linux 5.10-rc4; graphics alignment

Hi

Am 20.11.20 um 13:53 schrieb David Laight:
> From: Thomas Zimmermann
>> Sent: 20 November 2020 12:30
>>
>> Am 20.11.20 um 12:45 schrieb David Laight:
>>> From: Thomas Zimmermann
>>>> Sent: 20 November 2020 11:27
>>> ...
>>>>>> You can use drm-tip for testing, where many of the DRM patches go through.
>>>>>>
>>>>>>       https://cgit.freedesktop.org/drm/drm-tip/
>>>>>>
>>>>>> It's fairly up-to-date.
>>>>>
>>>>> Any idea of tags either side of the 5.10 merge?
>>>>
>>>> The final commit before v5.9 appears to be
>>>>
>>>>      Fixes: 33c8256b3bcc ("drm/amd/display: Change ABM config init interface")
>>>>
>>>> I'd try this as a good commit. For the bad commit, just try HEAD.
>>>
>>> HEAD off that tree works.
>>> Colours ok and no stack backtrace.
>>>
>>> Ideas??
>>
>> The good news is that it's been fixed. All you have to do is wait for
>> the fix to hit upstream.
>>
>> Did you try the patch that Dave linked?
> 
> That patch makes no difference to my system.
> The condition is false so it doesn't corrupt the flags.
> (I printed the values to see.)

I see, so it's probably something else that has been fixed in drm-tip. 
It's likely that at least one commit in drm-tip is also broken. I'd try 
to find one of these. One idea is to go through the commits that went 
into the related files. Maybe go back to the HEAD of drm-tip and try 
something like

   git log --oneline -- drivers/gpu/drm/ast/ 
drivers/gpu/drm/drm_gem_vram_helper.c drivers/gpu/drm/ttm/

That lists recent ast and memory-management commits. One of them might 
be broken and can serve an a starting point for a bisect.

I did a diff from v5.10-rc4 to drm-tip to look for suspicious changes. 
Some candidates are

   8e3784dfef8a ("drm/ast: Reload gamma LUT after changing primary 
plane's color format")
   2b8283ff1a60 ("drm/vram_helper: implement a ttm move callback.")
   6a6e5988a265 ("drm/ttm: replace last move_notify with delete_mem_notify")

I'd test them against their parent commits to see if anything changes.

Thanks for all your efforts!

Best regards
Thomas

> 
> 	David
> 
> -
> Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
> Registration No: 1397386 (Wales)
> 

-- 
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Felix Imendörffer

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