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drm/i915: Keep physical cursors pinned while in use 

The optimisation inherent in commit 6a2c4232ec ("drm/i915: Make the
physical object coherent with GTT") relies on that once we allocated a
cursor we would have coherent, zero overhead access to the scanout plane
holding the cursor. That is we could then do the very frequent cursor
updates X enjoys with no indirection or kernel involvement. However,
that all hinges on the GGTT mmap of the cursor being pinned and not
require refaulting on each access -- handling such a page fault likely
requires the busy GGTT to be rearranged causing a stall. A very simple
fix is then to handle the physical cursor exactly like other cursors and
keep its vma pinned while active.

References: https://bugs.freedesktop.org/show_bug.cgi?id=107600
References: 6a2c4232ec ("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/20180817082405.755-1-chris@chris-wilson.co.uk
This commit is contained in:
Chris Wilson 2018-08-17 09:24:05 +01:00
parent 70b73f9ac1
commit 4a47765103
1 changed files with 4 additions and 1 deletions
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5
drivers/gpu/drm/i915/intel_display.c
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@ -12969,8 +12969,11 @@ static int intel_plane_pin_fb(struct intel_plane_state *plane_state)
INTEL_INFO(dev_priv)->cursor_needs_physical) {
struct drm_i915_gem_object *obj = intel_fb_obj(fb);
const int align = intel_cursor_alignment(dev_priv);
int err;
return i915_gem_object_attach_phys(obj, align);
err = i915_gem_object_attach_phys(obj, align);
if (err)
return err;
}
vma = intel_pin_and_fence_fb_obj(fb,