[Intel-gfx] [PATCH v5] drm/i915: Pin the ifbdev for the info->system_base GGTT mmapping

[Takashi Iwai]

On Thu, 10 Dec 2015 17:36:04 +0100,
Ville Syrjälä wrote:
> 
> On Fri, Dec 04, 2015 at 04:05:26PM +0000, Chris Wilson wrote:
> > A long time ago (before 3.14) we relied on a permanent pinning of the
> > ifbdev to lock the fb in place inside the GGTT. However, the
> > introduction of stealing the BIOS framebuffer and reusing its address in
> > the GGTT for the fbdev has muddied waters and we use an inherited fb.
> > However, the inherited fb is only pinned whilst it is active and we no
> > longer have an explicit pin for the info->system_base mmapping used by
> > the fbdev. The result is that after some aperture pressure the fbdev may
> > be evicted, but we continue to write the fbcon into the same GGTT
> > address - overwriting anything else that may be put into that offset.
> > The effect is most pronounced across suspend/resume as
> > intel_fbdev_set_suspend() does a full clear over the whole scanout.
> > 
> > v2: Only unpin the intel_fb is we allocate it. If we inherit the fb from
> > the BIOS, we do not own the pinned vma (except for the reference we add
> > in this patch for our access via info->screen_base).
> > 
> > v3: Finish balancing the vma pinning for the normal !preallocated case.
> > 
> > v4: Try to simplify the pinning even further.
> > v5: Leak the VMA (cleaned up by object-free) to avoid complicated error paths.
> > 
> > Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> > Cc: "Goel, Akash" <akash.goel at intel.com>
> > Cc: Daniel Vetter <daniel.vetter at ffwll.ch>
> > Cc: Jesse Barnes <jbarnes at virtuousgeek.org>
> > Cc: Lukas Wunner <lukas at wunner.de>
> > Cc: stable at vger.kernel.org
> 
> This seems to have fixed my garbled text+fbcon dead after
> suspend/hibernate issues. Well, only had the patch in for a day or so,
> but so far so good.
> 
> Tested-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
> 
> Takashi, don't know if you already found this patch, but it's definitely
> something you should try as well.

Great, I'll give this a try.  Thanks!


Takashi