drm/i915/skl: Expose DC5/DC6 entry counts

The CSR firmware expose two counters, handy to check if we are indeed
entering DC5/DC6.

v2: Rebase
v3: Take RPM ref before reading (Imre)

Signed-off-by: Damien Lespiau <damien.lespiau@intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com> (v1)
Signed-off-by: Mika Kuoppala <mika.kuoppala@intel.com>
Reviewed-by: Imre Deak <imre.deak@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1446220412-32574-1-git-send-email-mika.kuoppala@intel.com
Tested-by: Daniel Stone <daniels@collabora.com> # SKL
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>

drivers/gpu/drm/i915/i915_debugfs.c

@@ -2811,6 +2811,17 @@ static int i915_dmc_info(struct seq_file *m, void *unused)
 	seq_printf(m, "version: %d.%d\n", CSR_VERSION_MAJOR(csr->version),
 		   CSR_VERSION_MINOR(csr->version));
 
+	intel_runtime_pm_get(dev_priv);
+
+	if (IS_SKYLAKE(dev) && csr->version >= CSR_VERSION(1, 6)) {
+		seq_printf(m, "DC3 -> DC5 count: %d\n",
+			   I915_READ(SKL_CSR_DC3_DC5_COUNT));
+		seq_printf(m, "DC5 -> DC6 count: %d\n",
+			   I915_READ(SKL_CSR_DC5_DC6_COUNT));
+	}
+
+	intel_runtime_pm_put(dev_priv);
+
 	return 0;
 }