[Intel-gfx] [PATCH] drm/i915: Work-around garbage DR4 from UXA

[Daniel Vetter]

Somehow UXA submits a completely bogus DR4 value since essentially
forever. It was originally introduced in

commit bade7d7d2505a10a8a7d24b084aff9742e2d6d64
Author: Eric Anholt <eric at anholt.net>
Date:   Fri Jun 6 14:03:25 2008 -0700

    Use the DRM for submitting batchbuffers when available.

and dutifully copied around ever since. Since we want to keep the
general dirt catching around just special case the UXA value.

This regression was introduced in

commit 9cb346648d9c529eccc5c7f30093e82d37004e37
Author: Daniel Vetter <daniel.vetter at ffwll.ch>
Date:   Thu Apr 24 08:09:11 2014 +0200

    drm/i915: Catch dirt in unused execbuffer fields

v2: Pimp commit message a bit and remove the double space.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=78494
Cc: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Jörg Otte <jrg.otte at gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter at ffwll.ch>
---
 drivers/gpu/drm/i915/i915_gem_execbuffer.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
index 47fe8ecef135..c7ee1e3013ac 100644
--- a/drivers/gpu/drm/i915/i915_gem_execbuffer.c
+++ b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
@@ -1168,6 +1168,11 @@ i915_gem_do_execbuffer(struct drm_device *dev, void *data,
 			goto pre_mutex_err;
 		}
 	} else {
+		if (args->DR4 == 0xffffffff) {
+			DRM_DEBUG("UXA submitting garbage DR4, fixing up\n");
+			args->DR4 = 0;
+		}
+
 		if (args->DR1 || args->DR4 || args->cliprects_ptr) {
 			DRM_DEBUG("0 cliprects but dirt in cliprects fields\n");
 			return -EINVAL;
-- 
1.9.2