i915/dp/fec: Configure the Forward Error Correction bits.

If FEC is supported, the corresponding
DP_TP_CTL register bits have to be configured.

The driver has to program the FEC_ENABLE in DP_TP_CTL[30] register
and wait till FEC_STATUS in DP_TP_CTL[28] is 1.
Also add the warn message to make sure that the control
register is already active while enabling FEC.

v2:
- Change commit message. Configure fec state after
  link training (Manasi, Gaurav)
- Remove redundent checks (Manasi)
- Remove the registers that get added automagically (Anusha)

v3: s/intel_dp_set_fec_state()/intel_dp_enable_fec_state() (Gaurav)

v4: rebased.

v5:
- Move the code to the proper spot, according to spec.(Ville)
- Use fec state as a check too.

v6: Pass intel_encoder, instead of intel_dp. (Ville)

v7: Remove unwanted comments (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/20181128202628.20238-16-manasi.d.navare@intel.com

1 files changed, 23 insertions, 0 deletions

diff --git a/drivers/gpu/drm/i915/intel_ddi.c b/drivers/gpu/drm/i915/intel_ddi.c
index 4c74bbe1cf73..12acdb08a750 100644
--- a/drivers/gpu/drm/i915/intel_ddi.c
+++ b/drivers/gpu/drm/i915/intel_ddi.c
@@ -3112,6 +3112,27 @@ static void intel_dp_sink_set_fec_ready(struct intel_dp *intel_dp,
 		DRM_DEBUG_KMS("Failed to set FEC_READY in the sink\n");
 }
 
+static void intel_ddi_enable_fec(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);
+
+	if (intel_wait_for_register(dev_priv, DP_TP_STATUS(port),
+				    DP_TP_STATUS_FEC_ENABLE_LIVE,
+				    DP_TP_STATUS_FEC_ENABLE_LIVE,
+				    1))
+		DRM_ERROR("Timed out waiting for FEC Enable Status\n");
+}
+
 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)
@@ -3157,6 +3178,8 @@ static void intel_ddi_pre_enable_dp(struct intel_encoder *encoder,
 	if (port != PORT_A || INTEL_GEN(dev_priv) >= 9)
 		intel_dp_stop_link_train(intel_dp);
 
+	intel_ddi_enable_fec(encoder, crtc_state);
+
 	icl_enable_phy_clock_gating(dig_port);
 
 	if (!is_mst)