drm/i915: Logically reorder error register capture

Create logical sections in an attempt to clean up, and continue to keep
future additions clean.

v2: Reworded the comments. Added section headers (Chris)
Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_gpu_error.c

@@ -985,41 +985,54 @@ static void i915_capture_reg_state(struct drm_i915_private *dev_priv,
 	struct drm_device *dev = dev_priv->dev;
 	int pipe;
 
-	error->eir = I915_READ(EIR);
-	error->pgtbl_er = I915_READ(PGTBL_ER);
-	if (HAS_HW_CONTEXTS(dev))
-		error->ccid = I915_READ(CCID);
+	/* General organization
+	 * 1. Registers specific to a single generation
+	 * 2. Registers which belong to multiple generations
+	 * 3. Feature specific registers.
+	 * 4. Everything else
+	 * Please try to follow the order.
+	 */
 
-	if (HAS_PCH_SPLIT(dev))
-		error->ier = I915_READ(DEIER) | I915_READ(GTIER);
-	else if (IS_VALLEYVIEW(dev))
+	/* 1: Registers specific to a single generation */
+	if (IS_VALLEYVIEW(dev)) {
 		error->ier = I915_READ(GTIER) | I915_READ(VLV_IER);
-	else if (IS_GEN2(dev))
-		error->ier = I915_READ16(IER);
-	else
-		error->ier = I915_READ(IER);
+		error->forcewake = I915_READ(FORCEWAKE_VLV);
+	}
 
-	if (INTEL_INFO(dev)->gen >= 6)
-		error->derrmr = I915_READ(DERRMR);
+	if (IS_GEN7(dev))
+		error->err_int = I915_READ(GEN7_ERR_INT);
 
-	if (IS_VALLEYVIEW(dev))
-		error->forcewake = I915_READ(FORCEWAKE_VLV);
-	else if (INTEL_INFO(dev)->gen >= 7)
-		error->forcewake = I915_READ(FORCEWAKE_MT);
-	else if (INTEL_INFO(dev)->gen == 6)
+	if (IS_GEN6(dev))
 		error->forcewake = I915_READ(FORCEWAKE);
 
-	if (!HAS_PCH_SPLIT(dev))
-		for_each_pipe(pipe)
-			error->pipestat[pipe] = I915_READ(PIPESTAT(pipe));
+	if (IS_GEN2(dev))
+		error->ier = I915_READ16(IER);
+
+	/* 2: Registers which belong to multiple generations */
+	if (INTEL_INFO(dev)->gen >= 7)
+		error->forcewake = I915_READ(FORCEWAKE_MT);
 
 	if (INTEL_INFO(dev)->gen >= 6) {
+		error->derrmr = I915_READ(DERRMR);
 		error->error = I915_READ(ERROR_GEN6);
 		error->done_reg = I915_READ(DONE_REG);
 	}
 
-	if (INTEL_INFO(dev)->gen == 7)
-		error->err_int = I915_READ(GEN7_ERR_INT);
+	/* 3: Feature specific registers */
+	if (HAS_HW_CONTEXTS(dev))
+		error->ccid = I915_READ(CCID);
+
+	if (HAS_PCH_SPLIT(dev))
+		error->ier = I915_READ(DEIER) | I915_READ(GTIER);
+	else {
+		error->ier = I915_READ(IER);
+		for_each_pipe(pipe)
+			error->pipestat[pipe] = I915_READ(PIPESTAT(pipe));
+	}
+
+	/* 4: Everything else */
+	error->eir = I915_READ(EIR);
+	error->pgtbl_er = I915_READ(PGTBL_ER);
 
 	i915_get_extra_instdone(dev, error->extra_instdone);
 }