[PATCH 3.16.y-ckt 074/216] drm/i915: Only warn the first time we attempt to mmio whilst suspended

[Luis Henriques]

3.16.7-ckt4 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Chris Wilson <chris at chris-wilson.co.uk>

commit 2b387059817fd100cddc5a97118d63e3f3fade74 upstream.

In all likelihood we will do a few hundred errnoneous register
operations if we do a single invalid register access whilst the device
is suspended. As each instance causes a WARN, this floods the system
logs and can make the system unresponsive.

The warning was first introduced in
commit b2ec142cb0101f298f8e091c7d75b1ec5b809b65
Author: Paulo Zanoni <paulo.r.zanoni at intel.com>
Date:   Fri Feb 21 13:52:25 2014 -0300

    drm/i915: call assert_device_not_suspended at gen6_force_wake_work

and despite the claims the WARN is still encountered in the wild today.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Paulo Zanoni <paulo.r.zanoni at intel.com>
Cc: Imre Deak <imre.deak at intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter at ffwll.ch>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 drivers/gpu/drm/i915/intel_uncore.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_uncore.c b/drivers/gpu/drm/i915/intel_uncore.c
index 4f6fef7ac069..28ac6156ec1d 100644
--- a/drivers/gpu/drm/i915/intel_uncore.c
+++ b/drivers/gpu/drm/i915/intel_uncore.c
@@ -43,8 +43,8 @@
 static void
 assert_device_not_suspended(struct drm_i915_private *dev_priv)
 {
-	WARN(HAS_RUNTIME_PM(dev_priv->dev) && dev_priv->pm.suspended,
-	     "Device suspended\n");
+	WARN_ONCE(HAS_RUNTIME_PM(dev_priv->dev) && dev_priv->pm.suspended,
+		  "Device suspended\n");
 }
 
 static void __gen6_gt_wait_for_thread_c0(struct drm_i915_private *dev_priv)
-- 
2.1.4