linux-kernel - [PATCH v2 0/2] Fix regression introduced by disabling accelerated scrolling in fbcon

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Message-Id: <20220124210319.325512-1-deller@gmx.de>
Date:   Mon, 24 Jan 2022 22:03:17 +0100
From:   Helge Deller <deller@....de>
To:     dri-devel@...ts.freedesktop.org, linux-fbdev@...r.kernel.org
Cc:     Javier Martinez Canillas <javierm@...hat.com>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Jani Nikula <jani.nikula@...ux.intel.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Gerd Hoffmann <kraxel@...hat.com>,
        Sven Schnelle <svens@...ckframe.org>,
        Claudio Suarez <cssk@...-c.es>, Pavel Machek <pavel@....cz>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Tomi Valkeinen <tomi.valkeinen@...com>,
        Ilia Mirkin <imirkin@...m.mit.edu>,
        Sam Ravnborg <sam@...nborg.org>,
        Daniel Vetter <daniel.vetter@...el.com>
Subject: [PATCH v2 0/2] Fix regression introduced by disabling accelerated scrolling in fbcon

This series reverts two patches which disabled scrolling acceleration in
fbcon/fbdev. Those patches introduced a regression for fbdev-supported graphic
cards because of the performance penalty by doing screen scrolling by software
instead of using existing 2D hardware acceleration.

This series has been discussed on linux-fbdev, dri-devel and linux-kernel
mailing lists. The consensus is that they will be reverted, but in addition
it's being worked on to find a solution which allows to disable parts of the
classic fbdev hardware acceleration code which isn't needed in DRM-only
configurations.

The patchset is planned to be kept in fbdev's for-next git branch and later
pushed into kernel v5.18 if no issues are found until then.

Helge

---
Changes in v2 compared to v1:
- adjusted the stable tags (one v5.10+, the other v5.16+)
- moved the analysis and reasoning why those should be reverted into
  the commit message. That simplifies to analyze later why they were
  reverted.
- resorted the To an Cc mail recipient lists

Helge Deller (2):
  Revert "fbdev: Garbage collect fbdev scrolling acceleration, part 1
    (from TODO list)"
  Revert "fbcon: Disable accelerated scrolling"

 Documentation/gpu/todo.rst              |  24 --
 drivers/video/fbdev/core/bitblit.c      |  16 +
 drivers/video/fbdev/core/fbcon.c        | 540 +++++++++++++++++++++++-
 drivers/video/fbdev/core/fbcon.h        |  59 +++
 drivers/video/fbdev/core/fbcon_ccw.c    |  28 +-
 drivers/video/fbdev/core/fbcon_cw.c     |  28 +-
 drivers/video/fbdev/core/fbcon_rotate.h |   9 +
 drivers/video/fbdev/core/fbcon_ud.c     |  37 +-
 drivers/video/fbdev/core/tileblit.c     |  16 +
 drivers/video/fbdev/skeletonfb.c        |  12 +-
 include/linux/fb.h                      |   2 +-
 11 files changed, 703 insertions(+), 68 deletions(-)

-- 
2.31.1