On 19.02.2016 10:06, Mario Kleiner wrote:
> This fixes a regression introduced in Linux 4.4.
>
> Limit the amount of time radeon_flip_work_func can
> delay programming a page flip, by both limiting the
> maximum amount of time per wait cycle and the maximum
> number of wait cycles. Continue the flip if the limit
> is exceeded, even if that may result in a visual or
> timing glitch.
>
> This is to prevent a hang of page flips, as reported
> in fdo bug #93746: Disconnecting a DisplayPort display
> in parallel to a kms pageflip getting queued can cause
> the following hang of page flips and thereby an unusable
> desktop:
>
> 1. kms pageflip ioctl() queues pageflip -> queues execution
> of radeon_flip_work_func.
>
> 2. Hotunplug of display causes the driver to DPMS OFF
> the unplugged display. Display engine shuts down,
> scanout no longer moves, but stays at its resting
> position at start line of vblank.
>
> 3. radeon_flip_work_func executes while crtc is off, and
> due to the non-moving scanout position, the new flip
> delay code introduced into Linux 4.4 by
> commit 5b5561b3660d ("drm/radeon: Fixup hw vblank counter/ts..")
> enters an infinite wait loop.
>
> 4. After reconnecting the display, the pageflip continues
> to hang in 3. and the display doesn't update its view
> of the desktop.
>
> This patch fixes the Linux 4.4 regression from fdo bug #93746
>
> <https://bugs.freedesktop.org/show_bug.cgi?id=93746>
>
> v2: Skip wait immediately if !radeon_crtc->enabled, as
> suggested by Michel.
>
> Reported-by: Bernd Steinhauser <linux@xxxxxxxxxxxxxxxxxxxx>
> Signed-off-by: Mario Kleiner <mario.kleiner.de@xxxxxxxxx>
> Tested-by: Bernd Steinhauser <linux@xxxxxxxxxxxxxxxxxxxx>
>
> Cc: <stable@xxxxxxxxxxxxxxx> # 4.4+
Both patches are
Reviewed-by: Michel Dänzer <michel.daenzer@xxxxxxx>
--
Earthling Michel Dänzer | http://www.amd.com
Libre software enthusiast | Mesa and X developer
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