drm/i915/fec: Disable FEC state.

Set the suitable bits in DP_TP_CTL to stop
bit correction when DSC is disabled.

v2:
- rebased.
- Add additional check for compression state. (Gaurav)

v3: rebased.

v4:
- Move the code to the proper spot according to spec (Ville)
- Use proper checks (manasi)

v5: Remove unnecessary checks (Ville)

v6: Resolve warnings. Add crtc_state as an argument to
intel_disable_ddi_buf(). (Manasi)

Cc: dri-devel@lists.freedesktop.org
Cc: Gaurav K Singh <gaurav.k.singh@intel.com>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Ville Syrjala <ville.syrjala@linux.intel.com>
Cc: Manasi Navare <manasi.d.navare@intel.com>
Signed-off-by: Anusha Srivatsa <anusha.srivatsa@intel.com>
Signed-off-by: Manasi Navare <manasi.d.navare@intel.com>
Reviewed-by: Manasi Navare <manasi.d.navare@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20181128202628.20238-17-manasi.d.navare@intel.com

drivers/gpu/drm/i915/intel_ddi.c

@@ -3133,6 +3133,22 @@ static void intel_ddi_enable_fec(struct intel_encoder *encoder,
 		DRM_ERROR("Timed out waiting for FEC Enable Status\n");
 }
 
+static void intel_ddi_disable_fec_state(struct intel_encoder *encoder,
+					const struct intel_crtc_state *crtc_state)
+{
+	struct drm_i915_private *dev_priv = to_i915(encoder->base.dev);
+	enum port port = encoder->port;
+	u32 val;
+
+	if (!crtc_state->fec_enable)
+		return;
+
+	val = I915_READ(DP_TP_CTL(port));
+	val &= ~DP_TP_CTL_FEC_ENABLE;
+	I915_WRITE(DP_TP_CTL(port), val);
+	POSTING_READ(DP_TP_CTL(port));
+}
+
 static void intel_ddi_pre_enable_dp(struct intel_encoder *encoder,
 				    const struct intel_crtc_state *crtc_state,
 				    const struct drm_connector_state *conn_state)
@@ -3272,7 +3288,8 @@ static void intel_ddi_pre_enable(struct intel_encoder *encoder,
 	}
 }
 
-static void intel_disable_ddi_buf(struct intel_encoder *encoder)
+static void intel_disable_ddi_buf(struct intel_encoder *encoder,
+				  const struct intel_crtc_state *crtc_state)
 {
 	struct drm_i915_private *dev_priv = to_i915(encoder->base.dev);
 	enum port port = encoder->port;
@@ -3291,6 +3308,9 @@ static void intel_disable_ddi_buf(struct intel_encoder *encoder)
 	val |= DP_TP_CTL_LINK_TRAIN_PAT1;
 	I915_WRITE(DP_TP_CTL(port), val);
 
+	/* Disable FEC in DP Sink */
+	intel_ddi_disable_fec_state(encoder, crtc_state);
+
 	if (wait)
 		intel_wait_ddi_buf_idle(dev_priv, port);
 }
@@ -3314,7 +3334,7 @@ static void intel_ddi_post_disable_dp(struct intel_encoder *encoder,
 		intel_dp_sink_dpms(intel_dp, DRM_MODE_DPMS_OFF);
 	}
 
-	intel_disable_ddi_buf(encoder);
+	intel_disable_ddi_buf(encoder, old_crtc_state);
 
 	intel_edp_panel_vdd_on(intel_dp);
 	intel_edp_panel_off(intel_dp);
@@ -3337,7 +3357,7 @@ static void intel_ddi_post_disable_hdmi(struct intel_encoder *encoder,
 
 	intel_ddi_disable_pipe_clock(old_crtc_state);
 
-	intel_disable_ddi_buf(encoder);
+	intel_disable_ddi_buf(encoder, old_crtc_state);
 
 	intel_display_power_put(dev_priv, dig_port->ddi_io_power_domain);
 
@@ -3388,7 +3408,7 @@ void intel_ddi_fdi_post_disable(struct intel_encoder *encoder,
 	val &= ~FDI_RX_ENABLE;
 	I915_WRITE(FDI_RX_CTL(PIPE_A), val);
 
-	intel_disable_ddi_buf(encoder);
+	intel_disable_ddi_buf(encoder, old_crtc_state);
 	intel_ddi_clk_disable(encoder);
 
 	val = I915_READ(FDI_RX_MISC(PIPE_A));