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[Bug 1142977] Missing Support for tearfree in modeset X driver
  • From: bugzilla_noreply@xxxxxxxxxx
  • Date: Fri, 26 Jul 2019 10:36:13 +0000
  • Message-id: <bug-1142977-21960-soNxVP1Am4@http.bugzilla.suse.com/>
http://bugzilla.suse.com/show_bug.cgi?id=1142977
http://bugzilla.suse.com/show_bug.cgi?id=1142977#c1

Stefan Dirsch <sndirsch@xxxxxxxx> changed:

What |Removed |Added
----------------------------------------------------------------------------
Priority|P5 - None |P2 - High
Status|NEW |CONFIRMED
Summary|Missing Support for |Missing Support for
|tearfree in modeset driver |tearfree in modeset X
| |driver
Severity|Major |Enhancement

--- Comment #1 from Stefan Dirsch <sndirsch@xxxxxxxx> ---
I should have mentioning that one of the goals of Wayland has been a tearfree
desktop (Wayland session can be selected in GDM login screen). If Wayland works
nicely on your laptop is a different question though.

Back to X.org. intel X driver supports tearfree, but is no longer recommded for
current Intel GPUs. :-(

Option "TearFree" "boolean"
Disable or enable TearFree updates. This option forces X to per-
form all rendering to a backbuffer prior to updating the actual
display. It requires an extra memory allocation the same size as
a framebuffer, the occasional extra copy, and requires Damage
tracking. Thus enabling TearFree requires more memory and is
slower (reduced throughput) and introduces a small amount of
output latency, but it should not impact input latency. However,
the update to the screen is then performed synchronously with
the vertical refresh of the display so that the entire update is
completed before the display starts its refresh. That is only
one frame is ever visible, preventing an unsightly tear between
two visible and differing frames. Note that this replicates what
the compositing manager should be doing, however TearFree will
redirect the compositor updates (and those of fullscreen games)
directly on to the scanout thus incurring no additional overhead
in the composited case. Also note that not all compositing man-
agers prevent tearing, and if the outputs are rotated, there
will still be tearing without TearFree enabled.

Default: TearFree is disabled.

In order to switch to intel you would need to install xf86-video-intel package
and restart you desktop. I'm afraid you'll also need to reconfigure
your monitor setup (intel uses differnt output names than modeset driver). And
you also would need the following
/etc/X11/xorg.conf.d/50-device.conf snippet for tearfree.

Section "Device"
Identifier "Default Device"
Driver "intel"
Option "TearFree" "on"
EndSection

I will open a ticket upstream, if/when tearfree in modeset driver is planned?
Since it's available in intel/amdgpu/radeon driver, it should also
be possible to implement in modeset driver.

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