linux-kernel - [PATCH 3.18 042/183] drm/i915: Only warn the first time we attempt to mmio whilst suspended

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Message-Id: <20150125180812.002264160@linuxfoundation.org>
Date:	Sun, 25 Jan 2015 10:06:04 -0800
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, Chris Wilson <chris@...is-wilson.co.uk>,
	Paulo Zanoni <paulo.r.zanoni@...el.com>,
	Imre Deak <imre.deak@...el.com>,
	Daniel Vetter <daniel.vetter@...ll.ch>
Subject: [PATCH 3.18 042/183] drm/i915: Only warn the first time we attempt to mmio whilst suspended

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

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

From: Chris Wilson <chris@...is-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@...el.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@...is-wilson.co.uk>
Cc: Paulo Zanoni <paulo.r.zanoni@...el.com>
Cc: Imre Deak <imre.deak@...el.com>
Signed-off-by: Daniel Vetter <daniel.vetter@...ll.ch>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/gpu/drm/i915/intel_uncore.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- 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)


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