[Intel-gfx] [PATCH 2/2] drm/i915: fully apply WaSkipStolenMemoryFirstPage

[Chris Wilson]

On Wed, Dec 14, 2016 at 12:55:38PM -0200, Paulo Zanoni wrote:
> Reserve the first page of stolen memory right after initializing the
> mm allocator. This means that we won't inherit the FB in case the BIOS
> decides to put it at the start of stolen. But the BIOS should not be
> putting it at the start of stolen since it's going to get corrupted. I
> suppose the bug here is that some pixels at the very top of the screen
> will be corrupted, so it's not exactly easy to notice.
> 
> We have confirmation that the first page of stolen does actually get
> corrupted, so I really think we should do this in order to avoid any
> possible future headaches, even if that means losing BIOS framebuffer
> inheritance. Let's not use the HW in a way it's not supposed to be
> used.
> 
> v2: don't even put the first page on the mm (Chris).
> 
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=94605
> Cc: Chris Wilson <chris at chris-wilson.co.uk>
> Signed-off-by: Paulo Zanoni <paulo.r.zanoni at intel.com>

Mental note: need to add to the list of test cases (insert_in_range >
range of drm_mm).

Reviewed-by: Chris Wilson <chris at chris-wilson.co.uk>
(code, I'll take your word that w/a accurately surmises the situation
and is the blessed strategy)
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre