Re: [PATCH 2/2] Revert "fbcon: Disable accelerated scrolling"

[Greg Kroah-Hartman]

On Wed, Jan 19, 2022 at 12:08:39PM +0100, Helge Deller wrote:
> This reverts commit 39aead8373b3c20bb5965c024dfb51a94e526151.
> 
> Revert this patch.  This patch started to introduce the regression that
> all hardware acceleration of more than 35 existing fbdev drivers were
> bypassed and thus fbcon console output for those was dramatically slowed
> down by factor of 10 and more.
> 
> Reverting this commit has no impact on DRM, since none of the DRM drivers are
> tagged with the acceleration flags FBINFO_HWACCEL_COPYAREA,
> FBINFO_HWACCEL_FILLRECT or others.
> 
> Signed-off-by: Helge Deller <deller@xxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx # v5.16

Why just 5.16?  This commit came in on 5.11 and was backported to
5.10.5.

As for "why", I think there was a number of private bugs that were
reported in this code, which is why it was removed.  I do not think it
can be safely added back in without addressing them first.  Let me go
dig through my email to see if I can find them...

thanks,

greg k-h