[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.

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

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..7d71e5c01fc8 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