drm/i915: Dump 'output_types' in crtc state dump

To make it easier to debug things let's dump the output types bitmask in
the crtc state dump. And to make life that much better, let's pretty
print it as a a human reaadable string as well.

v2: Have the caller pass in the buffer (Chris)
    #undef OUTPUT_TYPE (Jani)

Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171010121207.570-2-ville.syrjala@linux.intel.com
Reviewed-by: Jani Nikula <jani.nikula@intel.com>

drivers/gpu/drm/i915/intel_display.c

@@ -10662,6 +10662,52 @@ intel_dump_m_n_config(struct intel_crtc_state *pipe_config, char *id,
 		      m_n->link_m, m_n->link_n, m_n->tu);
 }
 
+#define OUTPUT_TYPE(x) [INTEL_OUTPUT_ ## x] = #x
+
+static const char * const output_type_str[] = {
+	OUTPUT_TYPE(UNUSED),
+	OUTPUT_TYPE(ANALOG),
+	OUTPUT_TYPE(DVO),
+	OUTPUT_TYPE(SDVO),
+	OUTPUT_TYPE(LVDS),
+	OUTPUT_TYPE(TVOUT),
+	OUTPUT_TYPE(HDMI),
+	OUTPUT_TYPE(DP),
+	OUTPUT_TYPE(EDP),
+	OUTPUT_TYPE(DSI),
+	OUTPUT_TYPE(UNKNOWN),
+	OUTPUT_TYPE(DP_MST),
+};
+
+#undef OUTPUT_TYPE
+
+static void snprintf_output_types(char *buf, size_t len,
+				  unsigned int output_types)
+{
+	char *str = buf;
+	int i;
+
+	str[0] = '\0';
+
+	for (i = 0; i < ARRAY_SIZE(output_type_str); i++) {
+		int r;
+
+		if ((output_types & BIT(i)) == 0)
+			continue;
+
+		r = snprintf(str, len, "%s%s",
+			     str != buf ? "," : "", output_type_str[i]);
+		if (r >= len)
+			break;
+		str += r;
+		len -= r;
+
+		output_types &= ~BIT(i);
+	}
+
+	WARN_ON_ONCE(output_types != 0);
+}
+
 static void intel_dump_pipe_config(struct intel_crtc *crtc,
 				   struct intel_crtc_state *pipe_config,
 				   const char *context)
@@ -10672,10 +10718,15 @@ static void intel_dump_pipe_config(struct intel_crtc *crtc,
 	struct intel_plane *intel_plane;
 	struct intel_plane_state *state;
 	struct drm_framebuffer *fb;
+	char buf[64];
 
 	DRM_DEBUG_KMS("[CRTC:%d:%s]%s\n",
 		      crtc->base.base.id, crtc->base.name, context);
 
+	snprintf_output_types(buf, sizeof(buf), pipe_config->output_types);
+	DRM_DEBUG_KMS("output_types: %s (0x%x)\n",
+		      buf, pipe_config->output_types);
+
 	DRM_DEBUG_KMS("cpu_transcoder: %s, pipe bpp: %i, dithering: %i\n",
 		      transcoder_name(pipe_config->cpu_transcoder),
 		      pipe_config->pipe_bpp, pipe_config->dither);