<feed xmlns='http://www.w3.org/2005/Atom'>
<title>linux-toradex.git/drivers/video, branch v5.17-rc4</title>
<subtitle>Linux kernel for Apalis and Colibri modules</subtitle>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/'/>
<entry>
<title>Merge tag 'drm-misc-fixes-2022-02-10' of git://anongit.freedesktop.org/drm/drm-misc into drm-fixes</title>
<updated>2022-02-11T02:06:15+00:00</updated>
<author>
<name>Dave Airlie</name>
<email>airlied@redhat.com</email>
</author>
<published>2022-02-11T02:05:04+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=df2bb4dc285e60665930889e6f8c5bb38b90249a'/>
<id>df2bb4dc285e60665930889e6f8c5bb38b90249a</id>
<content type='text'>
 * drm/panel: simple: Fix assignments from panel_dpi_probe()
 * drm/privacy-screen: Cleanups
 * drm/rockchip: Fix HDMI error cleanup; Fix RK3399 VOP register fields
 * drm/vc4: HDMI fixes; Cleanups
 * fbdev: Add fbdev core module with Daniel as maintainer; Cleanups

Signed-off-by: Dave Airlie &lt;airlied@redhat.com&gt;

From: Thomas Zimmermann &lt;tzimmermann@suse.de&gt;
Link: https://patchwork.freedesktop.org/patch/msgid/YgTf1Zsflzq3JSFo@linux-uq9g
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
 * drm/panel: simple: Fix assignments from panel_dpi_probe()
 * drm/privacy-screen: Cleanups
 * drm/rockchip: Fix HDMI error cleanup; Fix RK3399 VOP register fields
 * drm/vc4: HDMI fixes; Cleanups
 * fbdev: Add fbdev core module with Daniel as maintainer; Cleanups

Signed-off-by: Dave Airlie &lt;airlied@redhat.com&gt;

From: Thomas Zimmermann &lt;tzimmermann@suse.de&gt;
Link: https://patchwork.freedesktop.org/patch/msgid/YgTf1Zsflzq3JSFo@linux-uq9g
</pre>
</div>
</content>
</entry>
<entry>
<title>fbcon: Avoid 'cap' set but not used warning</title>
<updated>2022-02-08T13:44:15+00:00</updated>
<author>
<name>Helge Deller</name>
<email>deller@gmx.de</email>
</author>
<published>2022-02-07T15:59:31+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=50b10528aad568c95f772039d4b3093b4aea7439'/>
<id>50b10528aad568c95f772039d4b3093b4aea7439</id>
<content type='text'>
Fix this kernel test robot warning:

  drivers/video/fbdev/core/fbcon.c: In function 'fbcon_init':
  drivers/video/fbdev/core/fbcon.c:1028:6: warning: variable 'cap' set but not used [-Wunused-but-set-variable]

The cap variable is only used when CONFIG_FRAMEBUFFER_CONSOLE_LEGACY_ACCELERATION
is enabled. Drop the temporary variable and use info-&gt;flags instead.

Fixes: 87ab9f6b7417 ("Revert "fbcon: Disable accelerated scrolling")
Reported-by: kernel test robot &lt;lkp@intel.com&gt;
Signed-off-by: Helge Deller &lt;deller@gmx.de&gt;
Signed-off-by: Daniel Vetter &lt;daniel.vetter@ffwll.ch&gt;
Link: https://patchwork.freedesktop.org/patch/msgid/YgFB4xqI+As196FR@p100
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Fix this kernel test robot warning:

  drivers/video/fbdev/core/fbcon.c: In function 'fbcon_init':
  drivers/video/fbdev/core/fbcon.c:1028:6: warning: variable 'cap' set but not used [-Wunused-but-set-variable]

The cap variable is only used when CONFIG_FRAMEBUFFER_CONSOLE_LEGACY_ACCELERATION
is enabled. Drop the temporary variable and use info-&gt;flags instead.

Fixes: 87ab9f6b7417 ("Revert "fbcon: Disable accelerated scrolling")
Reported-by: kernel test robot &lt;lkp@intel.com&gt;
Signed-off-by: Helge Deller &lt;deller@gmx.de&gt;
Signed-off-by: Daniel Vetter &lt;daniel.vetter@ffwll.ch&gt;
Link: https://patchwork.freedesktop.org/patch/msgid/YgFB4xqI+As196FR@p100
</pre>
</div>
</content>
</entry>
<entry>
<title>Merge tag 'drm-misc-fixes-2022-02-03' of git://anongit.freedesktop.org/drm/drm-misc into drm-fixes</title>
<updated>2022-02-04T04:43:35+00:00</updated>
<author>
<name>Dave Airlie</name>
<email>airlied@redhat.com</email>
</author>
<published>2022-02-04T04:43:28+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=8ea2c5187d7b4901a70374415e772f1db422fb74'/>
<id>8ea2c5187d7b4901a70374415e772f1db422fb74</id>
<content type='text'>
 * dma-buf/heaps: Fix potential spectre v1 gadget
 * drm/kmb: Fix potential out-of-bounds access
 * drm/mxsfb: Fix NULL-pointer dereference
 * drm/nouveau: Fix potential out-of-bounds access in BIOS decoding
 * fbdev: Re-add support for fbcon hardware acceleration

Signed-off-by: Dave Airlie &lt;airlied@redhat.com&gt;

From: Thomas Zimmermann &lt;tzimmermann@suse.de&gt;
Link: https://patchwork.freedesktop.org/patch/msgid/Yfu8mTZQUNt1RwZd@linux-uq9g
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
 * dma-buf/heaps: Fix potential spectre v1 gadget
 * drm/kmb: Fix potential out-of-bounds access
 * drm/mxsfb: Fix NULL-pointer dereference
 * drm/nouveau: Fix potential out-of-bounds access in BIOS decoding
 * fbdev: Re-add support for fbcon hardware acceleration

Signed-off-by: Dave Airlie &lt;airlied@redhat.com&gt;

From: Thomas Zimmermann &lt;tzimmermann@suse.de&gt;
Link: https://patchwork.freedesktop.org/patch/msgid/Yfu8mTZQUNt1RwZd@linux-uq9g
</pre>
</div>
</content>
</entry>
<entry>
<title>fbdev: fbmem: Fix the implicit type casting</title>
<updated>2022-02-03T12:52:03+00:00</updated>
<author>
<name>Yizhuo Zhai</name>
<email>yzhai003@ucr.edu</email>
</author>
<published>2022-02-02T23:58:08+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=68e8cc2a23b61862bf20ffc9b782a3fb49c65568'/>
<id>68e8cc2a23b61862bf20ffc9b782a3fb49c65568</id>
<content type='text'>
In function do_fb_ioctl(), the "arg" is the type of unsigned long,
and in "case FBIOBLANK:" this argument is casted into an int before
passig to fb_blank(). In fb_blank(), the comparision
if (blank &gt; FB_BLANK_POWERDOWN) would be bypass if the original
"arg" is a large number, which is possible because it comes from
the user input. Fix this by adding the check before the function
call.

Reviewed-by: Guenter Roeck &lt;linux@roeck-us.net&gt;
Reviewed-by: Sam Ravnborg &lt;sam@ravnborg.org&gt;
Acked-by: Helge Deller &lt;deller@gmx.de&gt;
Signed-off-by: Yizhuo Zhai &lt;yzhai003@ucr.edu&gt;
Signed-off-by: Daniel Vetter &lt;daniel.vetter@ffwll.ch&gt;
Link: https://patchwork.freedesktop.org/patch/msgid/20220202235811.1621017-1-yzhai003@ucr.edu
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
In function do_fb_ioctl(), the "arg" is the type of unsigned long,
and in "case FBIOBLANK:" this argument is casted into an int before
passig to fb_blank(). In fb_blank(), the comparision
if (blank &gt; FB_BLANK_POWERDOWN) would be bypass if the original
"arg" is a large number, which is possible because it comes from
the user input. Fix this by adding the check before the function
call.

Reviewed-by: Guenter Roeck &lt;linux@roeck-us.net&gt;
Reviewed-by: Sam Ravnborg &lt;sam@ravnborg.org&gt;
Acked-by: Helge Deller &lt;deller@gmx.de&gt;
Signed-off-by: Yizhuo Zhai &lt;yzhai003@ucr.edu&gt;
Signed-off-by: Daniel Vetter &lt;daniel.vetter@ffwll.ch&gt;
Link: https://patchwork.freedesktop.org/patch/msgid/20220202235811.1621017-1-yzhai003@ucr.edu
</pre>
</div>
</content>
</entry>
<entry>
<title>fbcon: Add option to enable legacy hardware acceleration</title>
<updated>2022-02-02T14:16:26+00:00</updated>
<author>
<name>Helge Deller</name>
<email>deller@gmx.de</email>
</author>
<published>2022-02-02T13:55:31+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=a3f781a9d6114c1d1e01defb7aa234dec45d2a5f'/>
<id>a3f781a9d6114c1d1e01defb7aa234dec45d2a5f</id>
<content type='text'>
Add a config option CONFIG_FRAMEBUFFER_CONSOLE_LEGACY_ACCELERATION to
enable bitblt and fillrect hardware acceleration in the framebuffer
console. If disabled, such acceleration will not be used, even if it is
supported by the graphics hardware driver.

If you plan to use DRM as your main graphics output system, you should
disable this option since it will prevent compiling in code which isn't
used later on when DRM takes over.

For all other configurations, e.g. if none of your graphic cards support
DRM (yet), DRM isn't available for your architecture, or you can't be
sure that the graphic card in the target system will support DRM, you
most likely want to enable this option.

In the non-accelerated case (e.g. when DRM is used), the inlined
fb_scrollmode() function is hardcoded to return SCROLL_REDRAW and as such the
compiler is able to optimize much unneccesary code away.

In this v3 patch version I additionally changed the GETVYRES() and GETVXRES()
macros to take a pointer to the fbcon_display struct. This fixes the build when
console rotation is enabled and helps the compiler again to optimize out code.

Signed-off-by: Helge Deller &lt;deller@gmx.de&gt;
Cc: stable@vger.kernel.org # v5.10+
Signed-off-by: Helge Deller &lt;deller@gmx.de&gt;
Signed-off-by: Daniel Vetter &lt;daniel.vetter@ffwll.ch&gt;
Link: https://patchwork.freedesktop.org/patch/msgid/20220202135531.92183-4-deller@gmx.de
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Add a config option CONFIG_FRAMEBUFFER_CONSOLE_LEGACY_ACCELERATION to
enable bitblt and fillrect hardware acceleration in the framebuffer
console. If disabled, such acceleration will not be used, even if it is
supported by the graphics hardware driver.

If you plan to use DRM as your main graphics output system, you should
disable this option since it will prevent compiling in code which isn't
used later on when DRM takes over.

For all other configurations, e.g. if none of your graphic cards support
DRM (yet), DRM isn't available for your architecture, or you can't be
sure that the graphic card in the target system will support DRM, you
most likely want to enable this option.

In the non-accelerated case (e.g. when DRM is used), the inlined
fb_scrollmode() function is hardcoded to return SCROLL_REDRAW and as such the
compiler is able to optimize much unneccesary code away.

In this v3 patch version I additionally changed the GETVYRES() and GETVXRES()
macros to take a pointer to the fbcon_display struct. This fixes the build when
console rotation is enabled and helps the compiler again to optimize out code.

Signed-off-by: Helge Deller &lt;deller@gmx.de&gt;
Cc: stable@vger.kernel.org # v5.10+
Signed-off-by: Helge Deller &lt;deller@gmx.de&gt;
Signed-off-by: Daniel Vetter &lt;daniel.vetter@ffwll.ch&gt;
Link: https://patchwork.freedesktop.org/patch/msgid/20220202135531.92183-4-deller@gmx.de
</pre>
</div>
</content>
</entry>
<entry>
<title>Revert "fbcon: Disable accelerated scrolling"</title>
<updated>2022-02-02T14:15:11+00:00</updated>
<author>
<name>Helge Deller</name>
<email>deller@gmx.de</email>
</author>
<published>2022-02-02T13:55:30+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=87ab9f6b7417349aa197a6c7098d4fdd4beebb74'/>
<id>87ab9f6b7417349aa197a6c7098d4fdd4beebb74</id>
<content type='text'>
This reverts commit 39aead8373b3c20bb5965c024dfb51a94e526151.

Revert the first (of 2) commits which disabled scrolling acceleration in
fbcon/fbdev.  It introduced a regression for fbdev-supported graphic cards
because of the performance penalty by doing screen scrolling by software
instead of using the existing graphic card 2D hardware acceleration.

Console scrolling acceleration was disabled by dropping code which
checked at runtime the driver hardware capabilities for the
BINFO_HWACCEL_COPYAREA or FBINFO_HWACCEL_FILLRECT flags and if set, it
enabled scrollmode SCROLL_MOVE which uses hardware acceleration to move
screen contents.  After dropping those checks scrollmode was hard-wired
to SCROLL_REDRAW instead, which forces all graphic cards to redraw every
character at the new screen position when scrolling.

This change effectively disabled all hardware-based scrolling acceleration for
ALL drivers, because now all kind of 2D hardware acceleration (bitblt,
fillrect) in the drivers isn't used any longer.

The original commit message mentions that only 3 DRM drivers (nouveau, omapdrm
and gma500) used hardware acceleration in the past and thus code for checking
and using scrolling acceleration is obsolete.

This statement is NOT TRUE, because beside the DRM drivers there are around 35
other fbdev drivers which depend on fbdev/fbcon and still provide hardware
acceleration for fbdev/fbcon.

The original commit message also states that syzbot found lots of bugs in fbcon
and thus it's "often the solution to just delete code and remove features".
This is true, and the bugs - which actually affected all users of fbcon,
including DRM - were fixed, or code was dropped like e.g. the support for
software scrollback in vgacon (commit 973c096f6a85).

So to further analyze which bugs were found by syzbot, I've looked through all
patches in drivers/video which were tagged with syzbot or syzkaller back to
year 2005. The vast majority fixed the reported issues on a higher level, e.g.
when screen is to be resized, or when font size is to be changed. The few ones
which touched driver code fixed a real driver bug, e.g. by adding a check.

But NONE of those patches touched code of either the SCROLL_MOVE or the
SCROLL_REDRAW case.

That means, there was no real reason why SCROLL_MOVE had to be ripped-out and
just SCROLL_REDRAW had to be used instead. The only reason I can imagine so far
was that SCROLL_MOVE wasn't used by DRM and as such it was assumed that it
could go away. That argument completely missed the fact that SCROLL_MOVE is
still heavily used by fbdev (non-DRM) drivers.

Some people mention that using memcpy() instead of the hardware acceleration is
pretty much the same speed. But that's not true, at least not for older graphic
cards and machines where we see speed decreases by factor 10 and more and thus
this change leads to console responsiveness way worse than before.

That's why the original commit is to be reverted. By reverting we
reintroduce hardware-based scrolling acceleration and fix the
performance regression for fbdev drivers.

There isn't any impact on DRM when reverting those patches.

Signed-off-by: Helge Deller &lt;deller@gmx.de&gt;
Acked-by: Geert Uytterhoeven &lt;geert@linux-m68k.org&gt;
Acked-by: Sven Schnelle &lt;svens@stackframe.org&gt;
Cc: stable@vger.kernel.org # v5.10+
Signed-off-by: Helge Deller &lt;deller@gmx.de&gt;
Signed-off-by: Daniel Vetter &lt;daniel.vetter@ffwll.ch&gt;
Link: https://patchwork.freedesktop.org/patch/msgid/20220202135531.92183-3-deller@gmx.de
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
This reverts commit 39aead8373b3c20bb5965c024dfb51a94e526151.

Revert the first (of 2) commits which disabled scrolling acceleration in
fbcon/fbdev.  It introduced a regression for fbdev-supported graphic cards
because of the performance penalty by doing screen scrolling by software
instead of using the existing graphic card 2D hardware acceleration.

Console scrolling acceleration was disabled by dropping code which
checked at runtime the driver hardware capabilities for the
BINFO_HWACCEL_COPYAREA or FBINFO_HWACCEL_FILLRECT flags and if set, it
enabled scrollmode SCROLL_MOVE which uses hardware acceleration to move
screen contents.  After dropping those checks scrollmode was hard-wired
to SCROLL_REDRAW instead, which forces all graphic cards to redraw every
character at the new screen position when scrolling.

This change effectively disabled all hardware-based scrolling acceleration for
ALL drivers, because now all kind of 2D hardware acceleration (bitblt,
fillrect) in the drivers isn't used any longer.

The original commit message mentions that only 3 DRM drivers (nouveau, omapdrm
and gma500) used hardware acceleration in the past and thus code for checking
and using scrolling acceleration is obsolete.

This statement is NOT TRUE, because beside the DRM drivers there are around 35
other fbdev drivers which depend on fbdev/fbcon and still provide hardware
acceleration for fbdev/fbcon.

The original commit message also states that syzbot found lots of bugs in fbcon
and thus it's "often the solution to just delete code and remove features".
This is true, and the bugs - which actually affected all users of fbcon,
including DRM - were fixed, or code was dropped like e.g. the support for
software scrollback in vgacon (commit 973c096f6a85).

So to further analyze which bugs were found by syzbot, I've looked through all
patches in drivers/video which were tagged with syzbot or syzkaller back to
year 2005. The vast majority fixed the reported issues on a higher level, e.g.
when screen is to be resized, or when font size is to be changed. The few ones
which touched driver code fixed a real driver bug, e.g. by adding a check.

But NONE of those patches touched code of either the SCROLL_MOVE or the
SCROLL_REDRAW case.

That means, there was no real reason why SCROLL_MOVE had to be ripped-out and
just SCROLL_REDRAW had to be used instead. The only reason I can imagine so far
was that SCROLL_MOVE wasn't used by DRM and as such it was assumed that it
could go away. That argument completely missed the fact that SCROLL_MOVE is
still heavily used by fbdev (non-DRM) drivers.

Some people mention that using memcpy() instead of the hardware acceleration is
pretty much the same speed. But that's not true, at least not for older graphic
cards and machines where we see speed decreases by factor 10 and more and thus
this change leads to console responsiveness way worse than before.

That's why the original commit is to be reverted. By reverting we
reintroduce hardware-based scrolling acceleration and fix the
performance regression for fbdev drivers.

There isn't any impact on DRM when reverting those patches.

Signed-off-by: Helge Deller &lt;deller@gmx.de&gt;
Acked-by: Geert Uytterhoeven &lt;geert@linux-m68k.org&gt;
Acked-by: Sven Schnelle &lt;svens@stackframe.org&gt;
Cc: stable@vger.kernel.org # v5.10+
Signed-off-by: Helge Deller &lt;deller@gmx.de&gt;
Signed-off-by: Daniel Vetter &lt;daniel.vetter@ffwll.ch&gt;
Link: https://patchwork.freedesktop.org/patch/msgid/20220202135531.92183-3-deller@gmx.de
</pre>
</div>
</content>
</entry>
<entry>
<title>Revert "fbdev: Garbage collect fbdev scrolling acceleration, part 1 (from TODO list)"</title>
<updated>2022-02-02T14:14:56+00:00</updated>
<author>
<name>Helge Deller</name>
<email>deller@gmx.de</email>
</author>
<published>2022-02-02T13:55:29+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=1148836fd3226c20de841084aba24184d4fbbe77'/>
<id>1148836fd3226c20de841084aba24184d4fbbe77</id>
<content type='text'>
This reverts commit b3ec8cdf457e5e63d396fe1346cc788cf7c1b578.

Revert the second (of 2) commits which disabled scrolling acceleration
in fbcon/fbdev.  It introduced a regression for fbdev-supported graphic
cards because of the performance penalty by doing screen scrolling by
software instead of using the existing graphic card 2D hardware
acceleration.

Console scrolling acceleration was disabled by dropping code which
checked at runtime the driver hardware capabilities for the
BINFO_HWACCEL_COPYAREA or FBINFO_HWACCEL_FILLRECT flags and if set, it
enabled scrollmode SCROLL_MOVE which uses hardware acceleration to move
screen contents.  After dropping those checks scrollmode was hard-wired
to SCROLL_REDRAW instead, which forces all graphic cards to redraw every
character at the new screen position when scrolling.

This change effectively disabled all hardware-based scrolling acceleration for
ALL drivers, because now all kind of 2D hardware acceleration (bitblt,
fillrect) in the drivers isn't used any longer.

The original commit message mentions that only 3 DRM drivers (nouveau, omapdrm
and gma500) used hardware acceleration in the past and thus code for checking
and using scrolling acceleration is obsolete.

This statement is NOT TRUE, because beside the DRM drivers there are around 35
other fbdev drivers which depend on fbdev/fbcon and still provide hardware
acceleration for fbdev/fbcon.

The original commit message also states that syzbot found lots of bugs in fbcon
and thus it's "often the solution to just delete code and remove features".
This is true, and the bugs - which actually affected all users of fbcon,
including DRM - were fixed, or code was dropped like e.g. the support for
software scrollback in vgacon (commit 973c096f6a85).

So to further analyze which bugs were found by syzbot, I've looked through all
patches in drivers/video which were tagged with syzbot or syzkaller back to
year 2005. The vast majority fixed the reported issues on a higher level, e.g.
when screen is to be resized, or when font size is to be changed. The few ones
which touched driver code fixed a real driver bug, e.g. by adding a check.

But NONE of those patches touched code of either the SCROLL_MOVE or the
SCROLL_REDRAW case.

That means, there was no real reason why SCROLL_MOVE had to be ripped-out and
just SCROLL_REDRAW had to be used instead. The only reason I can imagine so far
was that SCROLL_MOVE wasn't used by DRM and as such it was assumed that it
could go away. That argument completely missed the fact that SCROLL_MOVE is
still heavily used by fbdev (non-DRM) drivers.

Some people mention that using memcpy() instead of the hardware acceleration is
pretty much the same speed. But that's not true, at least not for older graphic
cards and machines where we see speed decreases by factor 10 and more and thus
this change leads to console responsiveness way worse than before.

That's why the original commit is to be reverted. By reverting we
reintroduce hardware-based scrolling acceleration and fix the
performance regression for fbdev drivers.

There isn't any impact on DRM when reverting those patches.

Signed-off-by: Helge Deller &lt;deller@gmx.de&gt;
Acked-by: Geert Uytterhoeven &lt;geert@linux-m68k.org&gt;
Acked-by: Sven Schnelle &lt;svens@stackframe.org&gt;
Cc: stable@vger.kernel.org # v5.16+
Signed-off-by: Helge Deller &lt;deller@gmx.de&gt;
Signed-off-by: Daniel Vetter &lt;daniel.vetter@ffwll.ch&gt;
Link: https://patchwork.freedesktop.org/patch/msgid/20220202135531.92183-2-deller@gmx.de
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
This reverts commit b3ec8cdf457e5e63d396fe1346cc788cf7c1b578.

Revert the second (of 2) commits which disabled scrolling acceleration
in fbcon/fbdev.  It introduced a regression for fbdev-supported graphic
cards because of the performance penalty by doing screen scrolling by
software instead of using the existing graphic card 2D hardware
acceleration.

Console scrolling acceleration was disabled by dropping code which
checked at runtime the driver hardware capabilities for the
BINFO_HWACCEL_COPYAREA or FBINFO_HWACCEL_FILLRECT flags and if set, it
enabled scrollmode SCROLL_MOVE which uses hardware acceleration to move
screen contents.  After dropping those checks scrollmode was hard-wired
to SCROLL_REDRAW instead, which forces all graphic cards to redraw every
character at the new screen position when scrolling.

This change effectively disabled all hardware-based scrolling acceleration for
ALL drivers, because now all kind of 2D hardware acceleration (bitblt,
fillrect) in the drivers isn't used any longer.

The original commit message mentions that only 3 DRM drivers (nouveau, omapdrm
and gma500) used hardware acceleration in the past and thus code for checking
and using scrolling acceleration is obsolete.

This statement is NOT TRUE, because beside the DRM drivers there are around 35
other fbdev drivers which depend on fbdev/fbcon and still provide hardware
acceleration for fbdev/fbcon.

The original commit message also states that syzbot found lots of bugs in fbcon
and thus it's "often the solution to just delete code and remove features".
This is true, and the bugs - which actually affected all users of fbcon,
including DRM - were fixed, or code was dropped like e.g. the support for
software scrollback in vgacon (commit 973c096f6a85).

So to further analyze which bugs were found by syzbot, I've looked through all
patches in drivers/video which were tagged with syzbot or syzkaller back to
year 2005. The vast majority fixed the reported issues on a higher level, e.g.
when screen is to be resized, or when font size is to be changed. The few ones
which touched driver code fixed a real driver bug, e.g. by adding a check.

But NONE of those patches touched code of either the SCROLL_MOVE or the
SCROLL_REDRAW case.

That means, there was no real reason why SCROLL_MOVE had to be ripped-out and
just SCROLL_REDRAW had to be used instead. The only reason I can imagine so far
was that SCROLL_MOVE wasn't used by DRM and as such it was assumed that it
could go away. That argument completely missed the fact that SCROLL_MOVE is
still heavily used by fbdev (non-DRM) drivers.

Some people mention that using memcpy() instead of the hardware acceleration is
pretty much the same speed. But that's not true, at least not for older graphic
cards and machines where we see speed decreases by factor 10 and more and thus
this change leads to console responsiveness way worse than before.

That's why the original commit is to be reverted. By reverting we
reintroduce hardware-based scrolling acceleration and fix the
performance regression for fbdev drivers.

There isn't any impact on DRM when reverting those patches.

Signed-off-by: Helge Deller &lt;deller@gmx.de&gt;
Acked-by: Geert Uytterhoeven &lt;geert@linux-m68k.org&gt;
Acked-by: Sven Schnelle &lt;svens@stackframe.org&gt;
Cc: stable@vger.kernel.org # v5.16+
Signed-off-by: Helge Deller &lt;deller@gmx.de&gt;
Signed-off-by: Daniel Vetter &lt;daniel.vetter@ffwll.ch&gt;
Link: https://patchwork.freedesktop.org/patch/msgid/20220202135531.92183-2-deller@gmx.de
</pre>
</div>
</content>
</entry>
<entry>
<title>video: hyperv_fb: Fix validation of screen resolution</title>
<updated>2022-01-24T14:01:12+00:00</updated>
<author>
<name>Michael Kelley</name>
<email>mikelley@microsoft.com</email>
</author>
<published>2022-01-16T19:18:31+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=9ff5549b1d1d3c3a9d71220d44bd246586160f1d'/>
<id>9ff5549b1d1d3c3a9d71220d44bd246586160f1d</id>
<content type='text'>
In the WIN10 version of the Synthetic Video protocol with Hyper-V,
Hyper-V reports a list of supported resolutions as part of the protocol
negotiation. The driver calculates the maximum width and height from
the list of resolutions, and uses those maximums to validate any screen
resolution specified in the video= option on the kernel boot line.

This method of validation is incorrect. For example, the list of
supported resolutions could contain 1600x1200 and 1920x1080, both of
which fit in an 8 Mbyte frame buffer.  But calculating the max width
and height yields 1920 and 1200, and 1920x1200 resolution does not fit
in an 8 Mbyte frame buffer.  Unfortunately, this resolution is accepted,
causing a kernel fault when the driver accesses memory outside the
frame buffer.

Instead, validate the specified screen resolution by calculating
its size, and comparing against the frame buffer size.  Delete the
code for calculating the max width and height from the list of
resolutions, since these max values have no use.  Also add the
frame buffer size to the info message to aid in understanding why
a resolution might be rejected.

Fixes: 67e7cdb4829d ("video: hyperv: hyperv_fb: Obtain screen resolution from Hyper-V host")
Signed-off-by: Michael Kelley &lt;mikelley@microsoft.com&gt;
Reviewed-by: Haiyang Zhang &lt;haiyangz@microsoft.com&gt;
Acked-by: Helge Deller &lt;deller@gmx.de&gt;
Link: https://lore.kernel.org/r/1642360711-2335-1-git-send-email-mikelley@microsoft.com
Signed-off-by: Wei Liu &lt;wei.liu@kernel.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
In the WIN10 version of the Synthetic Video protocol with Hyper-V,
Hyper-V reports a list of supported resolutions as part of the protocol
negotiation. The driver calculates the maximum width and height from
the list of resolutions, and uses those maximums to validate any screen
resolution specified in the video= option on the kernel boot line.

This method of validation is incorrect. For example, the list of
supported resolutions could contain 1600x1200 and 1920x1080, both of
which fit in an 8 Mbyte frame buffer.  But calculating the max width
and height yields 1920 and 1200, and 1920x1200 resolution does not fit
in an 8 Mbyte frame buffer.  Unfortunately, this resolution is accepted,
causing a kernel fault when the driver accesses memory outside the
frame buffer.

Instead, validate the specified screen resolution by calculating
its size, and comparing against the frame buffer size.  Delete the
code for calculating the max width and height from the list of
resolutions, since these max values have no use.  Also add the
frame buffer size to the info message to aid in understanding why
a resolution might be rejected.

Fixes: 67e7cdb4829d ("video: hyperv: hyperv_fb: Obtain screen resolution from Hyper-V host")
Signed-off-by: Michael Kelley &lt;mikelley@microsoft.com&gt;
Reviewed-by: Haiyang Zhang &lt;haiyangz@microsoft.com&gt;
Acked-by: Helge Deller &lt;deller@gmx.de&gt;
Link: https://lore.kernel.org/r/1642360711-2335-1-git-send-email-mikelley@microsoft.com
Signed-off-by: Wei Liu &lt;wei.liu@kernel.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>Merge tag 'drm-next-2022-01-14' of git://anongit.freedesktop.org/drm/drm</title>
<updated>2022-01-16T04:52:38+00:00</updated>
<author>
<name>Linus Torvalds</name>
<email>torvalds@linux-foundation.org</email>
</author>
<published>2022-01-16T04:52:38+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=59d41458f143b7a20997b1e78b5c15d9d3e998c3'/>
<id>59d41458f143b7a20997b1e78b5c15d9d3e998c3</id>
<content type='text'>
Pull drm fixes from Daniel Vetter:
"drivers fixes:

   - i915 fixes for ttm backend + one pm wakelock fix

   - amdgpu fixes, fairly big pile of small things all over. Note this
     doesn't yet containe the fixed version of the otg sync patch that
     blew up

   - small driver fixes: meson, sun4i, vga16fb probe fix

  drm core fixes:

   - cma-buf heap locking

   - ttm compilation

   - self refresh helper state check

   - wrong error message in atomic helpers

   - mipi-dbi buffer mapping"

* tag 'drm-next-2022-01-14' of git://anongit.freedesktop.org/drm/drm: (49 commits)
  drm/mipi-dbi: Fix source-buffer address in mipi_dbi_buf_copy
  drm: fix error found in some cases after the patch d1af5cd86997
  drm/ttm: fix compilation on ARCH=um
  dma-buf: cma_heap: Fix mutex locking section
  video: vga16fb: Only probe for EGA and VGA 16 color graphic cards
  drm/amdkfd: Fix ASIC name typos
  drm/amdkfd: Fix DQM asserts on Hawaii
  drm/amdgpu: Use correct VIEWPORT_DIMENSION for DCN2
  drm/amd/pm: only send GmiPwrDnControl msg on master die (v3)
  drm/amdgpu: use spin_lock_irqsave to avoid deadlock by local interrupt
  drm/amdgpu: not return error on the init_apu_flags
  drm/amdkfd: Use prange-&gt;update_list head for remove_list
  drm/amdkfd: Use prange-&gt;list head for insert_list
  drm/amdkfd: make SPDX License expression more sound
  drm/amdkfd: Check for null pointer after calling kmemdup
  drm/amd/display: invalid parameter check in dmub_hpd_callback
  Revert "drm/amdgpu: Don't inherit GEM object VMAs in child process"
  drm/amd/display: reset dcn31 SMU mailbox on failures
  drm/amdkfd: use default_groups in kobj_type
  drm/amdgpu: use default_groups in kobj_type
  ...
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Pull drm fixes from Daniel Vetter:
"drivers fixes:

   - i915 fixes for ttm backend + one pm wakelock fix

   - amdgpu fixes, fairly big pile of small things all over. Note this
     doesn't yet containe the fixed version of the otg sync patch that
     blew up

   - small driver fixes: meson, sun4i, vga16fb probe fix

  drm core fixes:

   - cma-buf heap locking

   - ttm compilation

   - self refresh helper state check

   - wrong error message in atomic helpers

   - mipi-dbi buffer mapping"

* tag 'drm-next-2022-01-14' of git://anongit.freedesktop.org/drm/drm: (49 commits)
  drm/mipi-dbi: Fix source-buffer address in mipi_dbi_buf_copy
  drm: fix error found in some cases after the patch d1af5cd86997
  drm/ttm: fix compilation on ARCH=um
  dma-buf: cma_heap: Fix mutex locking section
  video: vga16fb: Only probe for EGA and VGA 16 color graphic cards
  drm/amdkfd: Fix ASIC name typos
  drm/amdkfd: Fix DQM asserts on Hawaii
  drm/amdgpu: Use correct VIEWPORT_DIMENSION for DCN2
  drm/amd/pm: only send GmiPwrDnControl msg on master die (v3)
  drm/amdgpu: use spin_lock_irqsave to avoid deadlock by local interrupt
  drm/amdgpu: not return error on the init_apu_flags
  drm/amdkfd: Use prange-&gt;update_list head for remove_list
  drm/amdkfd: Use prange-&gt;list head for insert_list
  drm/amdkfd: make SPDX License expression more sound
  drm/amdkfd: Check for null pointer after calling kmemdup
  drm/amd/display: invalid parameter check in dmub_hpd_callback
  Revert "drm/amdgpu: Don't inherit GEM object VMAs in child process"
  drm/amd/display: reset dcn31 SMU mailbox on failures
  drm/amdkfd: use default_groups in kobj_type
  drm/amdgpu: use default_groups in kobj_type
  ...
</pre>
</div>
</content>
</entry>
<entry>
<title>Merge tag 'drm-misc-fixes-2022-01-14' of git://anongit.freedesktop.org/drm/drm-misc into drm-next</title>
<updated>2022-01-14T14:17:17+00:00</updated>
<author>
<name>Daniel Vetter</name>
<email>daniel.vetter@ffwll.ch</email>
</author>
<published>2022-01-14T14:15:56+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=71e4a7029045e3904e0e9242b4a7cd84d47b8fe5'/>
<id>71e4a7029045e3904e0e9242b4a7cd84d47b8fe5</id>
<content type='text'>
Two DT bindings fixes for meson, a device refcounting fix for sun4i, a
probe fix for vga16fb, a locking fix for the CMA dma-buf heap and a
compilation fix for ttm.

Signed-off-by: Daniel Vetter &lt;daniel.vetter@ffwll.ch&gt;
[danvet: I made sure I have exactly the same conflict resolution as
Linus in 8d0749b4f83b ("Merge tag 'drm-next-2022-01-07' of
git://anongit.freedesktop.org/drm/drm") to avoid further conflict fun.
From: Maxime Ripard &lt;maxime@cerno.tech&gt;
Link: https://patchwork.freedesktop.org/patch/msgid/20220114125454.zs46ny52lrxk3ljz@houat
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Two DT bindings fixes for meson, a device refcounting fix for sun4i, a
probe fix for vga16fb, a locking fix for the CMA dma-buf heap and a
compilation fix for ttm.

Signed-off-by: Daniel Vetter &lt;daniel.vetter@ffwll.ch&gt;
[danvet: I made sure I have exactly the same conflict resolution as
Linus in 8d0749b4f83b ("Merge tag 'drm-next-2022-01-07' of
git://anongit.freedesktop.org/drm/drm") to avoid further conflict fun.
From: Maxime Ripard &lt;maxime@cerno.tech&gt;
Link: https://patchwork.freedesktop.org/patch/msgid/20220114125454.zs46ny52lrxk3ljz@houat
</pre>
</div>
</content>
</entry>
</feed>
