Using generic fbdev helpers breaks hibernation

[Alex Deucher]

Thanks Thomas.  I think this got me on the right track.

Alex

On Tue, Jun 21, 2022 at 6:25 AM Thomas Zimmermann <tzimmermann at suse.de> wrote:
>
> 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
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