[Intel-gfx] [PATCH] drm/i915: Flush everything on switching to the kernel_context

[Chris Wilson]

Even though all rendering should have been flushed at the end of the
previous requests, add an extra flush after switching to the
kernel_context. As the switch to the kernel_context is used when idling
the gpu (e.g. suspend), having an extra layer of paranoia to ensure
everything is flushed to memory seems sensible.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
---
 drivers/gpu/drm/i915/i915_gem_context.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/i915_gem_context.c b/drivers/gpu/drm/i915/i915_gem_context.c
index aee0f6d72d33..ce3139e5ec4c 100644
--- a/drivers/gpu/drm/i915/i915_gem_context.c
+++ b/drivers/gpu/drm/i915/i915_gem_context.c
@@ -620,7 +620,14 @@ int i915_gem_switch_to_kernel_context(struct drm_i915_private *dev_priv)
 								 GFP_KERNEL);
 		}
 
-		i915_add_request(req);
+		/*
+		 * Force a flush after the switch to ensure that all rendering
+		 * and operations prior to switching to the kernel context hits
+		 * memory. This should be guaranteed by the previous request,
+		 * but an extra layer of paranoia before we declare the system
+		 * idle (on suspend etc) is advisable!
+		 */
+		__i915_add_request(req, true);
 	}
 
 	return 0;
-- 
2.15.0