drm/i915/overlay: Allocate physical registers from stolen
Given that we are now reasonably confident in our ability to detect and reserve the stolen memory (physical memory reserved for graphics by the BIOS) for ourselves on most machines, we can put it to use. In this case, we need a page to hold the overlay registers. On an i915g running MythTv, H Buus noticed that commit 6a2c4232 Author: Chris Wilson <chris@chris-wilson.co.uk> Date: Tue Nov 4 04:51:40 2014 -0800 drm/i915: Make the physical object coherent with GTT introduced stuttering into his video playback. After discarding the likely suspect of it being the physical cursor updates, we were left with the use of the phys object for the overlay. And lo, if we completely avoid using the phys object (allocated just once on module load!) by switching to stolen memory, the stuttering goes away. For lack of a better explanation, claim victory and kill two birds with one stone. Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=107600 Fixes: 6a2c4232 ("drm/i915: Make the physical object coherent with GTT") Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk> Cc: Ville Syrjälä <ville.syrjala@linux.intel.com> Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com> Link: https://patchwork.freedesktop.org/patch/msgid/20180906190144.1272-1-chris@chris-wilson.co.uk
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