Using generic fbdev helpers breaks hibernation

[Thomas Zimmermann]

Hi

Am 21.06.22 um 00:02 schrieb Alex Deucher:
> Maybe someone more familiar with the generic drm fbdev helpers can
> help me understand why they don't work with hibernation, at least with
> AMD GPUs.  We converted amdgpu to use the generic helpers instead of
> rolling our own in this patch[1], but it seems to have broken
> hibernation[2].  amdgpu has always set mode_config.prefer_shadow = 1,
> but that seems to be the cause of the hibernation breakage with the
> generic helpers.  I've been staring at the code for a while now but I
> can't see why this fails.  Any pointers?

I don't the actual reason, but when I tried to convert radeon to generic 
fbdev emulation, I had to modify the fbdev code a bit. I don't see how 
this would apply to amdgpu, but you can find the patchset attached. See 
patches 1 and 2.

Best regards
Thomas

> 
> Thanks,
> 
> Alex
> 
> [1] - https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=087451f372bf76d971184caa258807b7c35aac8f
> [2] - https://bugzilla.kernel.org/show_bug.cgi?id=216119

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