[Intel-gfx] [PATCH] drm/i915/fbc: disable FBC on FIFO underruns

[Chris Wilson]

On Tue, Sep 13, 2016 at 10:38:57AM -0300, Paulo Zanoni wrote:
> Ever since I started working on FBC I was already aware that FBC can
> really amplify the FIFO underrun symptoms. On systems where FIFO
> underruns were harmless error messages, enabling FBC would cause the
> underruns to give black screens.
> 
> We recently tried to enable FBC on Haswell and got reports of a system
> that would hang after some hours of uptime, and the first bad commit
> was the one that enabled FBC. We also observed that this system had
> FIFO underrun error messages on its dmesg. Although we don't have any
> evidence that fixing the underruns would solve the bug and make FBC
> work properly on this machine, IMHO it's better if we minimize the
> amount of possible problems by just giving up FBC whenever we detect
> an underrun.
> 
> v2: New version, different implementation and commit message.
> v3: Clarify the fact that we run from an IRQ handler (Chris).
> v4: Also add the underrun_detected check at can_choose() to avoid
>     misleading dmesg messages (DK).
> v5: Fix Engrish, use READ_ONCE on the unlocked read (Chris).
> 
> Cc: Stefan Richter <stefanr at s5r6.in-berlin.de>
> Cc: Lyude <cpaul at redhat.com>
> Cc: stevenhoneyman at gmail.com <stevenhoneyman at gmail.com>
> Cc: Dhinakaran Pandiyan <dhinakaran.pandiyan at intel.com>
> Cc: Chris Wilson <chris at chris-wilson.co.uk>
> Signed-off-by: Paulo Zanoni <paulo.r.zanoni at intel.com>

Looks like it does what you describe, so
Reviewed-by: Chris Wilson <chris at chris-wilson.co.uk>
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre