Re: [PATCH v4] drm/i915: Limit Valleyview and earlier to only using mappable scanout

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Mon, Nov 07, 2016 at 11:01:28AM +0000, Chris Wilson wrote:
> Valleyview appears tobe limited to only scanning out from the first 512MiB
> of the Global GTT. Lets presume that this behaviour was inherited from the
> display block copied from g4x (not Ironlake) and all earlier generations
> are similarly affected, thought testing suggests different symptoms. For
> simplicity, impose that these platforms must scanout from the mappable
> region. (For extra simplicity, use HAS_GMCH_DISPLAY even though this
> catches Cherryview which does not appear to be limited to the low
> aperture for its scanout.)
> 
> v2: Use HAS_GMCH_DISPLAY() to more clearly convey my intent about
> limiting this workaround to the old style of display engine.
> 
> v3: Update change log to reflect testing by Ville Syrjälä
> v4: Include the changes to the comments as well
> 
> Reported-by: Luis Botello <luis.botello.ortega@intel.com>
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=98036
> Fixes: 2efb813d5388 ("drm/i915: Fallback to using unmappable memory for scanout")
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Akash Goel <akash.goel@intel.com>
> Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
> Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
> Cc: <drm-intel-fixes@lists.freedesktop.org> # v4.9-rc1+
> ---
>  drivers/gpu/drm/i915/i915_gem.c | 19 +++++++++++++++++--
>  1 file changed, 17 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> index 6a2005683f6d..4116809f3ed2 100644
> --- a/drivers/gpu/drm/i915/i915_gem.c
> +++ b/drivers/gpu/drm/i915/i915_gem.c
> @@ -3673,8 +3673,23 @@ i915_gem_object_pin_to_display_plane(struct drm_i915_gem_object *obj,
>  	if (view->type == I915_GGTT_VIEW_NORMAL)
>  		vma = i915_gem_object_ggtt_pin(obj, view, 0, alignment,
>  					       PIN_MAPPABLE | PIN_NONBLOCK);
> -	if (IS_ERR(vma))
> -		vma = i915_gem_object_ggtt_pin(obj, view, 0, alignment, 0);
> +	if (IS_ERR(vma)) {
> +		struct drm_i915_private *i915 = to_i915(obj->base.dev);
> +		unsigned int flags;
> +
> +		/* Valleyview is definitely limited to scanning out the first
> +		 * 512MiB respectively. Lets presume this behaviour was
                          ^^^^^^^^^^^^

With that word removed this is
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>

> +		 * inherited from the g4x display engine and that all earlier
> +		 * gen are similarly limited. Testing suggests that it is a
> +		 * little more complicated than this. For example, Cherryview
> +		 * appears quite happy to scanout from anywhere within its
> +		 * global aperture.
> +		 */
> +		flags = 0;
> +		if (HAS_GMCH_DISPLAY(i915))
> +			flags = PIN_MAPPABLE;
> +		vma = i915_gem_object_ggtt_pin(obj, view, 0, alignment, flags);
> +	}
>  	if (IS_ERR(vma))
>  		goto err_unpin_display;
>  
> -- 
> 2.10.2

-- 
Ville Syrjälä
Intel OTC
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