drm/i915: Flush everything on switching to the kernel_context

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@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171126214856.23702-1-chris@chris-wilson.co.uk
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>

diff --git a/drivers/gpu/drm/i915/i915_gem_context.c b/drivers/gpu/drm/i915/i915_gem_context.c
index aee0f6d..ce3139e 100644 (file)
--- 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;