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

[Jani Nikula <jani.nikula@linux.intel.com>]

On Fri, 04 Nov 2016, Chris Wilson <chris@chris-wilson.co.uk> wrote:
> Valleyview and Cherryview are definitely limited to only scanning out
> from the first 256MiB and 512MiB of the Global GTT respectively. Lets
> presume that this behaviour was inherited from the display block copied
> from g4x (not Ironlake) and all earlier generations are similarly
> affected. For simplicity, impose that these platforms must scanout from
> the mappable region.
>
> 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: <drm-intel-fixes@lists.freedesktop.org> # v4.9-rc1+
> ---
> This leaves Ironlake -> Haswell with a bit of uncertainity. It is also
> not clear if the scanout accessible region is similarly limited on all
> gen8+, and so whether we need to similarly curtain the upper range for
> their scanouts.
> ---
>  drivers/gpu/drm/i915/i915_gem.c | 18 ++++++++++++++++--
>  1 file changed, 16 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> index 269e2487c104..408875fbec66 100644
> --- a/drivers/gpu/drm/i915/i915_gem.c
> +++ b/drivers/gpu/drm/i915/i915_gem.c
> @@ -3661,8 +3661,22 @@ 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 and Cherryview are definitely limited to scanning
> +		 * out the first 256MiB and 512MiB respectively. Lets presume
> +		 * this behaviour was inherited from their g4x display engine
> +		 * and that all earlier gen are similarly limited.
> +		 */
> +		flags = 0;
> +		if (INTEL_GEN(i915) < 5 ||
> +		    IS_VALLEYVIEW(i915) ||
> +		    IS_CHERRYVIEW(i915))

Since it's related to the display engine, HAS_GMCH_DISPLAY()?

BR,
Jani.

> +			flags = PIN_MAPPABLE;
> +		vma = i915_gem_object_ggtt_pin(obj, view, 0, alignment, flags);
> +	}
>  	if (IS_ERR(vma))
>  		goto err_unpin_display;

-- 
Jani Nikula, Intel Open Source Technology Center
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