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

[Chris Wilson]

On Wed, Oct 07, 2015 at 11:34:17AM -0700, Wayne Boyer wrote:
> From: Chris Wilson <chris at chris-wilson.co.uk>
> 
> 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: rebased on latest nightly (Wayne)
> 
> 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: stable at vger.kernel.org
> Reviewed-by: Deepak S <deepak.s at linux.intel.com>
> Signed-off-by: Wayne Boyer <wayne.boyer at intel.com>
> ---
>  drivers/gpu/drm/i915/intel_fbdev.c | 15 +++++++++++++++
>  1 file changed, 15 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/intel_fbdev.c b/drivers/gpu/drm/i915/intel_fbdev.c
> index 6532912..c6aa4f9 100644
> --- a/drivers/gpu/drm/i915/intel_fbdev.c
> +++ b/drivers/gpu/drm/i915/intel_fbdev.c
> @@ -215,6 +215,16 @@ static int intelfb_create(struct drm_fb_helper *helper,
>  	obj = intel_fb->obj;
>  	size = obj->base.size;
>  
> +	/* The fb constructor will have already pinned us (or inherited a
> +	 * GGTT region from the BIOS) suitable for a scanout, so
> +	 * this should just be a no-op and increment the pin count for the
> +	 * fbdev mmapping. It does have a useful side-effect of validating
> +	 * the pin for fbdev's use via a GGTT mmapping.
> +	 */
> +	ret = i915_gem_object_ggtt_pin(obj, NULL, 0, PIN_MAPPABLE);

This should be i915_gem_obj_ggtt_pin(obj, 0, PIN_MAPPABLE);
At which point I just rage quit.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre