[Intel-gfx] [PATCH 04/11] drm/i915: Clear scanline waits after disabling the pipe.

[Jesse Barnes]

On Wed, 11 Aug 2010 10:31:29 +0100
Chris Wilson <chris at chris-wilson.co.uk> wrote:

> If we disable the pipe and the GPU is currently waiting on a scanline
> WAIT_FOR_EVENT, the GPU will hang. Fortunately, there is a magic bit
> which we can write on i915+ to break this wait after disabling the
> pipe.
> 
> References:
> 
>   Bug 29252 - [Arrandale] Hung WAIT_FOR_EVENT when running rss-glx-skyrocket
>   https://bugs.freedesktop.org/show_bug.cgi?id=29252
> 
>   Bug 28964 - [i965gm] GPU infinite MI_WAIT_FOR_EVENT while watching video in Totem
>   https://bugs.freedesktop.org/show_bug.cgi?id=28964
> 
> and many others.
> 
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Jesse Barnes <jbarnes at virtuousgeek.org>
> ---
>  drivers/gpu/drm/i915/i915_reg.h      |    2 ++
>  drivers/gpu/drm/i915/intel_display.c |   31 +++++++++++++++++++++++++++++--
>  2 files changed, 31 insertions(+), 2 deletions(-)

Have we confirmed that this one actually works?  It seems safe enough,
though Eric's comment about idling things first still applies, right?

-- 
Jesse Barnes, Intel Open Source Technology Center