[v3 6/7] i915/dp/fec: Configure the Forward Error Correction bits.

[Anusha Srivatsa <anusha.srivatsa@intel.com>]

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.

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>
---
 drivers/gpu/drm/i915/i915_reg.h  |  2 ++
 drivers/gpu/drm/i915/intel_ddi.c | 27 +++++++++++++++++++++++++++
 drivers/gpu/drm/i915/intel_drv.h |  2 ++
 3 files changed, 31 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index e85f53cb9cdd..8b1753939299 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -9134,6 +9134,7 @@ enum skl_power_gate {
 #define _DP_TP_CTL_B			0x64140
 #define DP_TP_CTL(port) _MMIO_PORT(port, _DP_TP_CTL_A, _DP_TP_CTL_B)
 #define  DP_TP_CTL_ENABLE			(1 << 31)
+#define  DP_TP_CTL_FEC_ENABLE			(1 << 30)
 #define  DP_TP_CTL_MODE_SST			(0 << 27)
 #define  DP_TP_CTL_MODE_MST			(1 << 27)
 #define  DP_TP_CTL_FORCE_ACT			(1 << 25)
@@ -9152,6 +9153,7 @@ enum skl_power_gate {
 #define _DP_TP_STATUS_A			0x64044
 #define _DP_TP_STATUS_B			0x64144
 #define DP_TP_STATUS(port) _MMIO_PORT(port, _DP_TP_STATUS_A, _DP_TP_STATUS_B)
+#define  DP_TP_STATUS_FEC_ENABLE_LIVE		(1 << 28)
 #define  DP_TP_STATUS_IDLE_DONE			(1 << 25)
 #define  DP_TP_STATUS_ACT_SENT			(1 << 24)
 #define  DP_TP_STATUS_MODE_STATUS_MST		(1 << 23)
diff --git a/drivers/gpu/drm/i915/intel_ddi.c b/drivers/gpu/drm/i915/intel_ddi.c
index efbada95dc4e..5badeaefb539 100644
--- a/drivers/gpu/drm/i915/intel_ddi.c
+++ b/drivers/gpu/drm/i915/intel_ddi.c
@@ -2889,6 +2889,29 @@ static void intel_ddi_clk_disable(struct intel_encoder *encoder)
 	}
 }
 
+void intel_dp_enable_fec_state(struct intel_dp *intel_dp,
+			       const struct intel_crtc_state *crtc_state)
+{
+	struct drm_i915_private *dev_priv = dp_to_i915(intel_dp);
+	struct intel_digital_port *intel_dig_port = dp_to_dig_port(intel_dp);
+	enum port port = intel_dig_port->base.port;
+	u32 val;
+
+	/* FEC support exists for DP 1.4 only */
+	if (!crtc_state->can_fec)
+		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)
@@ -2934,9 +2957,13 @@ static void intel_ddi_pre_enable_dp(struct intel_encoder *encoder,
 					      DP_DECOMPRESSION_EN);
 	intel_dp_sink_set_fec_ready(intel_dp, crtc_state, DP_FEC_READY);
 	intel_dp_start_link_train(intel_dp);
+
 	if (port != PORT_A || INTEL_GEN(dev_priv) >= 9)
 		intel_dp_stop_link_train(intel_dp);
 
+	/* Set FEC state after link training */
+	intel_dp_enable_fec_state(intel_dp, crtc_state);
+
 	icl_enable_phy_clock_gating(dig_port);
 
 	if (!is_mst)
diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
index a15ecdb4a706..405a44b3b3a8 100644
--- a/drivers/gpu/drm/i915/intel_drv.h
+++ b/drivers/gpu/drm/i915/intel_drv.h
@@ -1799,6 +1799,8 @@ void intel_dp_sink_set_decompression_state(struct intel_dp *intel_dp,
 void intel_dp_sink_set_fec_ready(struct intel_dp *intel_dp,
 				 const struct intel_crtc_state *crtc_state,
 				 int state);
+void intel_dp_enable_fec_state(struct intel_dp *intel_dp,
+			       const struct intel_crtc_state *crtc_state);
 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);
-- 
2.17.1

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