drm/i915: add rc6 residency times to debugfs

RC6 residency should be in intervals of 1.28us, and the counter wraps.
Here is an example using awk to get the various RC6 and RC6+ residency
times in seconds, since boot.

cat /sys/kernel/debug/dri/0/i915_drpc_info  | grep residency | awk -F':' -F' '  '{print $5 * 1.28 / 1000000}'

This is primarily for QA, but has other applications as well. An
upcoming patch to add interfaces should be more interesting to
application developers.

v2: move comment to the correct place

v3: display with %u instead of %d, for Ouping

CC: Ouping Zhang <ouping.zhang@intel.com>
Reviewed-by: Eugeni Dodonov <eugeni.dodonov@intel.com>
Signed-off-by: Ben Widawsky <benjamin.widawsky@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_debugfs.c

@@ -1171,6 +1171,17 @@ static int gen6_drpc_info(struct seq_file *m)
 
 	seq_printf(m, "Core Power Down: %s\n",
 		   yesno(gt_core_status & GEN6_CORE_CPD_STATE_MASK));
+
+	/* Not exactly sure what this is */
+	seq_printf(m, "RC6 \"Locked to RPn\" residency since boot: %u\n",
+		   I915_READ(GEN6_GT_GFX_RC6_LOCKED));
+	seq_printf(m, "RC6 residency since boot: %u\n",
+		   I915_READ(GEN6_GT_GFX_RC6));
+	seq_printf(m, "RC6+ residency since boot: %u\n",
+		   I915_READ(GEN6_GT_GFX_RC6p));
+	seq_printf(m, "RC6++ residency since boot: %u\n",
+		   I915_READ(GEN6_GT_GFX_RC6pp));
+
 	return 0;
 }
 

drivers/gpu/drm/i915/i915_reg.h

@@ -3970,6 +3970,11 @@
 						 GEN6_PM_RP_DOWN_THRESHOLD | \
 						 GEN6_PM_RP_DOWN_TIMEOUT)
 
+#define GEN6_GT_GFX_RC6_LOCKED			0x138104
+#define GEN6_GT_GFX_RC6				0x138108
+#define GEN6_GT_GFX_RC6p			0x13810C
+#define GEN6_GT_GFX_RC6pp			0x138110
+
 #define GEN6_PCODE_MAILBOX			0x138124
 #define   GEN6_PCODE_READY			(1<<31)
 #define   GEN6_READ_OC_PARAMS			0xc