Hello Greg,

On 1/19/22 12:47, Geert Uytterhoeven wrote:

On Wed, Jan 19, 2022 at 12:28 PM Greg Kroah-Hartman
[off-list ref] wrote:

quoted

On Wed, Jan 19, 2022 at 12:22:55PM +0100, Greg Kroah-Hartman wrote:

quoted

On Wed, Jan 19, 2022 at 12:08:39PM +0100, Helge Deller wrote:

quoted

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@gmx.de>

quoted

quoted

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...

Ah, no, that was just the soft scrollback code I was thinking of, which

Right.
That was commit 973c096f6a85 and it was about vgacon, not fbcon.

I did mentioned it in my cover letter, together with my analysis of
the reported bugs.

Maybe I should have put all the information from the cover letter into
the patch here as well. If you haven't read the cover letter yet, please do.

Helge

So the bugs argument is moot.

quoted

was a different revert and is still gone, thankfully :)

FTR, not everyone else was thankful about that one...

quoted

This one was just removed because Daniel noticed that only 3 drivers
used this (nouveau, omapdrm, and gma600), so this shouldn't have caused
any regressions in any other drivers like you are reporting here.

So perhaps this regression is caused by something else?

1. Daniel's patch was not CCed to linux-fbdev,
2. When I discovered the patch, I pointed out that the premise of 3
   drivers was not true, and that it affects 32 more fbdev drivers[1] .
   The patch was applied regardless.
3. When the patch was suggested for backporting, I pointed out the
   same[2].
   The patch was backported regardless.

[1] https://lore.kernel.org/r/alpine.DEB.2.22.394.2010311116530.379363@ramsan.of.borg/ (local)
[2] https://lore.kernel.org/r/CAMuHMdXRgam2zahPEGcw8+76Xm-0AO-Ci9-YmVa5JpTKVHphRw@mail.gmail.com/ (local)

Gr{oetje,eeting}s,

                        Geert