drm/i915: Consolidate unclaimed mmio detection

Access the unclaimed reg detection register through
one helper which also does cleanup. Note that we now access
the register only if the platform has the actual non claimed
access bit. This prevents reading the register with gens that
doesn't have the register or the unclaimed bit,
when debug_mmio > 0.

Note that we post after clearing the bit. This makes sure
that the next unclaimed write access would get detected
also if it happened right after clearing, and not fold
into the previous detection.

v2: s/unclaimed_reg_access/check_for_unclaimed_mmio (Chris)
    debug log on unclaimed detection on uncore init (Joonas)

v3: remove posting read (Ville)

Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Paulo Zanoni <przanoni@gmail.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Mika Kuoppala <mika.kuoppala@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1450200287-24080-1-git-send-email-mika.kuoppala@intel.com

drivers/gpu/drm/i915/intel_uncore.c

@@ -327,13 +327,31 @@ static void intel_uncore_ellc_detect(struct drm_device *dev)
 	}
 }
 
+static bool
+check_for_unclaimed_mmio(struct drm_i915_private *dev_priv)
+{
+	u32 dbg;
+
+	if (!HAS_FPGA_DBG_UNCLAIMED(dev_priv))
+		return false;
+
+	dbg = __raw_i915_read32(dev_priv, FPGA_DBG);
+	if (likely(!(dbg & FPGA_DBG_RM_NOCLAIM)))
+		return false;
+
+	__raw_i915_write32(dev_priv, FPGA_DBG, FPGA_DBG_RM_NOCLAIM);
+
+	return true;
+}
+
 static void __intel_uncore_early_sanitize(struct drm_device *dev,
 					  bool restore_forcewake)
 {
 	struct drm_i915_private *dev_priv = dev->dev_private;
 
-	if (HAS_FPGA_DBG_UNCLAIMED(dev))
-		__raw_i915_write32(dev_priv, FPGA_DBG, FPGA_DBG_RM_NOCLAIM);
+	/* clear out unclaimed reg detection bit */
+	if (check_for_unclaimed_mmio(dev_priv))
+		DRM_DEBUG("unclaimed mmio detected on uncore init, clearing\n");
 
 	/* clear out old GT FIFO errors */
 	if (IS_GEN6(dev) || IS_GEN7(dev))
@@ -594,10 +612,9 @@ hsw_unclaimed_reg_debug(struct drm_i915_private *dev_priv,
 	if (!i915.mmio_debug)
 		return;
 
-	if (__raw_i915_read32(dev_priv, FPGA_DBG) & FPGA_DBG_RM_NOCLAIM) {
+	if (check_for_unclaimed_mmio(dev_priv)) {
 		WARN(1, "Unclaimed register detected %s %s register 0x%x\n",
 		     when, op, i915_mmio_reg_offset(reg));
-		__raw_i915_write32(dev_priv, FPGA_DBG, FPGA_DBG_RM_NOCLAIM);
 		i915.mmio_debug--; /* Only report the first N failures */
 	}
 }
@@ -610,11 +627,10 @@ hsw_unclaimed_reg_detect(struct drm_i915_private *dev_priv)
 	if (i915.mmio_debug || !mmio_debug_once)
 		return;
 
-	if (__raw_i915_read32(dev_priv, FPGA_DBG) & FPGA_DBG_RM_NOCLAIM) {
+	if (check_for_unclaimed_mmio(dev_priv)) {
 		DRM_DEBUG("Unclaimed register detected, "
 			  "enabling oneshot unclaimed register reporting. "
 			  "Please use i915.mmio_debug=N for more information.\n");
-		__raw_i915_write32(dev_priv, FPGA_DBG, FPGA_DBG_RM_NOCLAIM);
 		i915.mmio_debug = mmio_debug_once--;
 	}
 }
@@ -1582,11 +1598,6 @@ bool intel_has_gpu_reset(struct drm_device *dev)
 
 void intel_uncore_check_errors(struct drm_device *dev)
 {
-	struct drm_i915_private *dev_priv = dev->dev_private;
-
-	if (HAS_FPGA_DBG_UNCLAIMED(dev) &&
-	    (__raw_i915_read32(dev_priv, FPGA_DBG) & FPGA_DBG_RM_NOCLAIM)) {
+	if (check_for_unclaimed_mmio(to_i915(dev)))
 		DRM_ERROR("Unclaimed register before interrupt\n");
-		__raw_i915_write32(dev_priv, FPGA_DBG, FPGA_DBG_RM_NOCLAIM);
-	}
 }