FAILED: patch "[PATCH] drm/i915: Unconditionally flush any chipset buffers before" failed to apply to 4.7-stable tree

[<gregkh@linuxfoundation.org>]

The patch below does not apply to the 4.7-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

>From dcd79934b0dd803fdb29216fbd6f4a899a66f466 Mon Sep 17 00:00:00 2001
From: Chris Wilson <chris@chris-wilson.co.uk>
Date: Thu, 18 Aug 2016 17:16:40 +0100
Subject: [PATCH] drm/i915: Unconditionally flush any chipset buffers before
 execbuf
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If userspace is asynchronously streaming into the batch or other
execobjects, we may not flush those writes along with a change in cache
domain (as there is no change). Therefore those writes may end up in
internal chipset buffers and not visible to the GPU upon execution. We
must issue a flush command or otherwise we encounter incoherency in the
batchbuffers and the GPU executing invalid commands (i.e. hanging) quite
regularly.

v2: Throw a paranoid wmb() into the general flush so that we remain
consistent with before.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=90841
Fixes: 1816f9236303 ("drm/i915: Support creation of unbound wc user...")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Akash Goel <akash.goel@intel.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
Tested-by: Matti Hämäläinen <ccr@tnsp.org>
Cc: stable@vger.kernel.org
Reviewed-by: Mika Kuoppala <mika.kuoppala@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20160818161718.27187-1-chris@chris-wilson.co.uk
(cherry picked from commit 600f436801deae65e48404847b61c89b4944e355)
Signed-off-by: Jani Nikula <jani.nikula@intel.com>

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 20fe9d52e256..3ca674e9c105 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -3591,6 +3591,7 @@ int i915_gem_evict_vm(struct i915_address_space *vm, bool do_idle);
 /* belongs in i915_gem_gtt.h */
 static inline void i915_gem_chipset_flush(struct drm_i915_private *dev_priv)
 {
+	wmb();
 	if (INTEL_GEN(dev_priv) < 6)
 		intel_gtt_chipset_flush();
 }
diff --git a/drivers/gpu/drm/i915/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
index 1978633e7549..b35e5b6475b2 100644
--- a/drivers/gpu/drm/i915/i915_gem_execbuffer.c
+++ b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
@@ -943,8 +943,6 @@ i915_gem_execbuffer_move_to_gpu(struct drm_i915_gem_request *req,
 {
 	const unsigned other_rings = ~intel_engine_flag(req->engine);
 	struct i915_vma *vma;
-	uint32_t flush_domains = 0;
-	bool flush_chipset = false;
 	int ret;
 
 	list_for_each_entry(vma, vmas, exec_list) {
@@ -957,16 +955,11 @@ i915_gem_execbuffer_move_to_gpu(struct drm_i915_gem_request *req,
 		}
 
 		if (obj->base.write_domain & I915_GEM_DOMAIN_CPU)
-			flush_chipset |= i915_gem_clflush_object(obj, false);
-
-		flush_domains |= obj->base.write_domain;
+			i915_gem_clflush_object(obj, false);
 	}
 
-	if (flush_chipset)
-		i915_gem_chipset_flush(req->engine->i915);
-
-	if (flush_domains & I915_GEM_DOMAIN_GTT)
-		wmb();
+	/* Unconditionally flush any chipset caches (for streaming writes). */
+	i915_gem_chipset_flush(req->engine->i915);
 
 	/* Unconditionally invalidate gpu caches and ensure that we do flush
 	 * any residual writes from the previous batch.