drm/i915/dp: Enable/Disable DSC in DP Sink

This patch enables decompression support in sink device
before link training and disables the same during the
DDI disabling.

v3 (From manasi):
* Pass bool state to enable/disable (Ville)
v2:(From Manasi)
* Change the enable/disable function to take crtc_state
instead of intel_dp as an argument (Manasi)
* Use the compression_enable flag as part of crtc_state (Manasi)

Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Ville Syrjala <ville.syrjala@linux.intel.com>
Cc: Anusha Srivatsa <anusha.srivatsa@intel.com>
Cc: Gaurav K Singh <gaurav.k.singh@intel.com>
Signed-off-by: Gaurav K Singh <gaurav.k.singh@intel.com>
Signed-off-by: Manasi Navare <manasi.d.navare@intel.com>
Reviewed-by: Anusha Srivatsa <anusha.srivatsa@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20181128202628.20238-6-manasi.d.navare@intel.com

drivers/gpu/drm/i915/intel_ddi.c

@@ -3134,6 +3134,8 @@ static void intel_ddi_pre_enable_dp(struct intel_encoder *encoder,
 	intel_ddi_init_dp_buf_reg(encoder);
 	if (!is_mst)
 		intel_dp_sink_dpms(intel_dp, DRM_MODE_DPMS_ON);
+	intel_dp_sink_set_decompression_state(intel_dp, crtc_state,
+					      true);
 	intel_dp_start_link_train(intel_dp);
 	if (port != PORT_A || INTEL_GEN(dev_priv) >= 9)
 		intel_dp_stop_link_train(intel_dp);
@@ -3491,6 +3493,9 @@ static void intel_disable_ddi_dp(struct intel_encoder *encoder,
 	intel_edp_drrs_disable(intel_dp, old_crtc_state);
 	intel_psr_disable(intel_dp, old_crtc_state);
 	intel_edp_backlight_off(old_conn_state);
+	/* Disable the decompression in DP Sink */
+	intel_dp_sink_set_decompression_state(intel_dp, old_crtc_state,
+					      false);
 }
 
 static void intel_disable_ddi_hdmi(struct intel_encoder *encoder,

drivers/gpu/drm/i915/intel_dp.c

@@ -2857,6 +2857,22 @@ static bool downstream_hpd_needs_d0(struct intel_dp *intel_dp)
 		intel_dp->downstream_ports[0] & DP_DS_PORT_HPD;
 }
 
+void intel_dp_sink_set_decompression_state(struct intel_dp *intel_dp,
+					   const struct intel_crtc_state *crtc_state,
+					   bool enable)
+{
+	int ret;
+
+	if (!crtc_state->dsc_params.compression_enable)
+		return;
+
+	ret = drm_dp_dpcd_writeb(&intel_dp->aux, DP_DSC_ENABLE,
+				 enable ? DP_DECOMPRESSION_EN : 0);
+	if (ret < 0)
+		DRM_DEBUG_KMS("Failed to %s sink decompression state\n",
+			      enable ? "enable" : "disable");
+}
+
 /* If the sink supports it, try to set the power state appropriately */
 void intel_dp_sink_dpms(struct intel_dp *intel_dp, int mode)
 {

drivers/gpu/drm/i915/intel_drv.h

@@ -1802,6 +1802,9 @@ void intel_dp_stop_link_train(struct intel_dp *intel_dp);
 int intel_dp_retrain_link(struct intel_encoder *encoder,
 			  struct drm_modeset_acquire_ctx *ctx);
 void intel_dp_sink_dpms(struct intel_dp *intel_dp, int mode);
+void intel_dp_sink_set_decompression_state(struct intel_dp *intel_dp,
+					   const struct intel_crtc_state *crtc_state,
+					   bool enable);
 void intel_dp_encoder_reset(struct drm_encoder *encoder);
 void intel_dp_encoder_suspend(struct intel_encoder *intel_encoder);
 void intel_dp_encoder_destroy(struct drm_encoder *encoder);