drm/i915/bxt: add dsi transcoders

The BXT display connections have DSI transcoders A and C that can be
muxed to any pipe, not unlike the eDP transcoder. Add the notion of DSI
transcoders.

The "normal" transcoders A, B and C are not used with BXT DSI, so care
must be taken to avoid accessing those registers with DSI transcoders in
the hardware state readout, modeset, and generally everywhere.

v2: addressing comments by Ville:
 - rename the dsi get config function to hsw_get_dsi_transcoder_state
 - rebase onto the higher level split of pipe/transcoder functions
 - use more has_dsi_encoder as we can now because of the above,
   with no need to look at the transcoder so much
 - rename IS_DSI_TRANSCODER to transcoder_is_dsi
 - use the above a bit more instead of comparing to < TRANSCODER_EDP

Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/299740536b7941e31b2744f3ce34f7afe936a771.1458313400.git.jani.nikula@intel.com
diff --git a/drivers/gpu/drm/i915/intel_runtime_pm.c b/drivers/gpu/drm/i915/intel_runtime_pm.c
index 2e88a5e..d189a00 100644
--- a/drivers/gpu/drm/i915/intel_runtime_pm.c
+++ b/drivers/gpu/drm/i915/intel_runtime_pm.c
@@ -89,6 +89,10 @@
 		return "TRANSCODER_C";
 	case POWER_DOMAIN_TRANSCODER_EDP:
 		return "TRANSCODER_EDP";
+	case POWER_DOMAIN_TRANSCODER_DSI_A:
+		return "TRANSCODER_DSI_A";
+	case POWER_DOMAIN_TRANSCODER_DSI_C:
+		return "TRANSCODER_DSI_C";
 	case POWER_DOMAIN_PORT_DDI_A_LANES:
 		return "PORT_DDI_A_LANES";
 	case POWER_DOMAIN_PORT_DDI_B_LANES:
@@ -419,6 +423,8 @@
 	BXT_DISPLAY_POWERWELL_2_POWER_DOMAINS |		\
 	BIT(POWER_DOMAIN_PIPE_A) |			\
 	BIT(POWER_DOMAIN_TRANSCODER_EDP) |		\
+	BIT(POWER_DOMAIN_TRANSCODER_DSI_A) |		\
+	BIT(POWER_DOMAIN_TRANSCODER_DSI_C) |		\
 	BIT(POWER_DOMAIN_PIPE_A_PANEL_FITTER) |		\
 	BIT(POWER_DOMAIN_PORT_DDI_A_LANES) |		\
 	BIT(POWER_DOMAIN_PORT_DSI) |			\