From c82297fcfaff2862686094061772070e6763e00c Mon Sep 17 00:00:00 2001
From: Chris Wilson <chris@chris-wilson.co.uk>
Date: Sun, 26 Nov 2017 21:48:56 +0000
Subject: [PATCH] drm/i915: Flush everything on switching to the kernel_context
Git-commit: c82297fcfaff2862686094061772070e6763e00c
Patch-mainline: v4.16-rc1
References: FATE#322643 bsc#1055900

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>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 drivers/gpu/drm/i915/i915_gem_context.c |    9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

--- 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(st
 								 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;