drm/i915: do not read swizzle info if unavailable

Since gen8 we don't use swizzle anymore. Don't dump registers related to
it: registers may or may not be there.

v2: pull the rest of driver state reporting before the read out (Chris)

Cc: Matt Roper <matthew.d.roper@intel.com>
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20200702200714.1278-1-lucas.demarchi@intel.com

drivers/gpu/drm/i915/i915_debugfs.c

@@ -1138,13 +1138,20 @@ static int i915_swizzle_info(struct seq_file *m, void *data)
 	struct intel_uncore *uncore = &dev_priv->uncore;
 	intel_wakeref_t wakeref;
 
-	wakeref = intel_runtime_pm_get(&dev_priv->runtime_pm);
-
 	seq_printf(m, "bit6 swizzle for X-tiling = %s\n",
 		   swizzle_string(dev_priv->ggtt.bit_6_swizzle_x));
 	seq_printf(m, "bit6 swizzle for Y-tiling = %s\n",
 		   swizzle_string(dev_priv->ggtt.bit_6_swizzle_y));
 
+	if (dev_priv->quirks & QUIRK_PIN_SWIZZLED_PAGES)
+		seq_puts(m, "L-shaped memory detected\n");
+
+	/* On BDW+, swizzling is not used. See detect_bit_6_swizzle() */
+	if (INTEL_GEN(dev_priv) >= 8 || IS_VALLEYVIEW(dev_priv))
+		return 0;
+
+	wakeref = intel_runtime_pm_get(&dev_priv->runtime_pm);
+
 	if (IS_GEN_RANGE(dev_priv, 3, 4)) {
 		seq_printf(m, "DDC = 0x%08x\n",
 			   intel_uncore_read(uncore, DCC));
@@ -1173,9 +1180,6 @@ static int i915_swizzle_info(struct seq_file *m, void *data)
 			   intel_uncore_read(uncore, DISP_ARB_CTL));
 	}
 
-	if (dev_priv->quirks & QUIRK_PIN_SWIZZLED_PAGES)
-		seq_puts(m, "L-shaped memory detected\n");
-
 	intel_runtime_pm_put(&dev_priv->runtime_pm, wakeref);
 
 	return 0;