[PATCH 4.8 037/125] drm/i915: Just clear the mmiodebug before a register access

[Greg Kroah-Hartman]

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

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

From: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>

commit f856f847b22c52be82f712ea6ada946c6db884d7 upstream.

When we enable the per-register access mmiodebug, it is to detect which
access is illegal. Reporting on earlier untraced access outside of the
mmiodebug does not help debugging (as the suspicion is immediately put
upon the current register which is not at fault)!

References: https://bugs.freedesktop.org/show_bug.cgi?id=97985
Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Cc: Mika Kuoppala <mika.kuoppala@xxxxxxxxx>
Reviewed-by: Mika Kuoppala <mika.kuoppala@xxxxxxxxx>
Link: http://patchwork.freedesktop.org/patch/msgid/20161003124516.12388-1-chris@xxxxxxxxxxxxxxxxxx
(cherry picked from commit dda960335e020835f7f1c12760e7f0b525b451e2)
Signed-off-by: Jani Nikula <jani.nikula@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/gpu/drm/i915/intel_uncore.c |    7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

--- a/drivers/gpu/drm/i915/intel_uncore.c
+++ b/drivers/gpu/drm/i915/intel_uncore.c
@@ -796,10 +796,9 @@ __unclaimed_reg_debug(struct drm_i915_pr
 		      const bool read,
 		      const bool before)
 {
-	if (WARN(check_for_unclaimed_mmio(dev_priv),
-		 "Unclaimed register detected %s %s register 0x%x\n",
-		 before ? "before" : "after",
-		 read ? "reading" : "writing to",
+	if (WARN(check_for_unclaimed_mmio(dev_priv) && !before,
+		 "Unclaimed %s register 0x%x\n",
+		 read ? "read from" : "write to",
 		 i915_mmio_reg_offset(reg)))
 		i915.mmio_debug--; /* Only report the first N failures */
 }