drm/i915/icl: DSI vswing programming sequence

This patch setup voltage swing before enabling
combo PHY DDI (shared with DSI).
Note that DSI voltage swing programming is for
high speed data buffers. HW automatically handles
the voltage swing for the low power data buffers.

v2: Rebase
v3: Address various review comments related to VSWING
    programming (Jani N)
Signed-off-by: Madhav Chauhan <madhav.chauhan@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/1537095223-5184-3-git-send-email-madhav.chauhan@intel.com

drivers/gpu/drm/i915/icl_dsi.c

@@ -27,6 +27,71 @@
 
 #include "intel_dsi.h"
 
+static void dsi_program_swing_and_deemphasis(struct intel_encoder *encoder)
+{
+	struct drm_i915_private *dev_priv = to_i915(encoder->base.dev);
+	struct intel_dsi *intel_dsi = enc_to_intel_dsi(&encoder->base);
+	enum port port;
+	u32 tmp;
+	int lane;
+
+	for_each_dsi_port(port, intel_dsi->ports) {
+
+		/*
+		 * Program voltage swing and pre-emphasis level values as per
+		 * table in BSPEC under DDI buffer programing
+		 */
+		tmp = I915_READ(ICL_PORT_TX_DW5_LN0(port));
+		tmp &= ~(SCALING_MODE_SEL_MASK | RTERM_SELECT_MASK);
+		tmp |= SCALING_MODE_SEL(0x2);
+		tmp |= TAP2_DISABLE | TAP3_DISABLE;
+		tmp |= RTERM_SELECT(0x6);
+		I915_WRITE(ICL_PORT_TX_DW5_GRP(port), tmp);
+
+		tmp = I915_READ(ICL_PORT_TX_DW5_AUX(port));
+		tmp &= ~(SCALING_MODE_SEL_MASK | RTERM_SELECT_MASK);
+		tmp |= SCALING_MODE_SEL(0x2);
+		tmp |= TAP2_DISABLE | TAP3_DISABLE;
+		tmp |= RTERM_SELECT(0x6);
+		I915_WRITE(ICL_PORT_TX_DW5_AUX(port), tmp);
+
+		tmp = I915_READ(ICL_PORT_TX_DW2_LN0(port));
+		tmp &= ~(SWING_SEL_LOWER_MASK | SWING_SEL_UPPER_MASK |
+			 RCOMP_SCALAR_MASK);
+		tmp |= SWING_SEL_UPPER(0x2);
+		tmp |= SWING_SEL_LOWER(0x2);
+		tmp |= RCOMP_SCALAR(0x98);
+		I915_WRITE(ICL_PORT_TX_DW2_GRP(port), tmp);
+
+		tmp = I915_READ(ICL_PORT_TX_DW2_AUX(port));
+		tmp &= ~(SWING_SEL_LOWER_MASK | SWING_SEL_UPPER_MASK |
+			 RCOMP_SCALAR_MASK);
+		tmp |= SWING_SEL_UPPER(0x2);
+		tmp |= SWING_SEL_LOWER(0x2);
+		tmp |= RCOMP_SCALAR(0x98);
+		I915_WRITE(ICL_PORT_TX_DW2_AUX(port), tmp);
+
+		tmp = I915_READ(ICL_PORT_TX_DW4_AUX(port));
+		tmp &= ~(POST_CURSOR_1_MASK | POST_CURSOR_2_MASK |
+			 CURSOR_COEFF_MASK);
+		tmp |= POST_CURSOR_1(0x0);
+		tmp |= POST_CURSOR_2(0x0);
+		tmp |= CURSOR_COEFF(0x3f);
+		I915_WRITE(ICL_PORT_TX_DW4_AUX(port), tmp);
+
+		for (lane = 0; lane <= 3; lane++) {
+			/* Bspec: must not use GRP register for write */
+			tmp = I915_READ(ICL_PORT_TX_DW4_LN(port, lane));
+			tmp &= ~(POST_CURSOR_1_MASK | POST_CURSOR_2_MASK |
+				 CURSOR_COEFF_MASK);
+			tmp |= POST_CURSOR_1(0x0);
+			tmp |= POST_CURSOR_2(0x0);
+			tmp |= CURSOR_COEFF(0x3f);
+			I915_WRITE(ICL_PORT_TX_DW4_LN(port, lane), tmp);
+		}
+	}
+}
+
 static void gen11_dsi_program_esc_clk_div(struct intel_encoder *encoder)
 {
 	struct drm_i915_private *dev_priv = to_i915(encoder->base.dev);
@@ -141,6 +206,58 @@ static void gen11_dsi_config_phy_lanes_sequence(struct intel_encoder *encoder)
 
 }
 
+static void gen11_dsi_voltage_swing_program_seq(struct intel_encoder *encoder)
+{
+	struct drm_i915_private *dev_priv = to_i915(encoder->base.dev);
+	struct intel_dsi *intel_dsi = enc_to_intel_dsi(&encoder->base);
+	u32 tmp;
+	enum port port;
+
+	/* clear common keeper enable bit */
+	for_each_dsi_port(port, intel_dsi->ports) {
+		tmp = I915_READ(ICL_PORT_PCS_DW1_LN0(port));
+		tmp &= ~COMMON_KEEPER_EN;
+		I915_WRITE(ICL_PORT_PCS_DW1_GRP(port), tmp);
+		tmp = I915_READ(ICL_PORT_PCS_DW1_AUX(port));
+		tmp &= ~COMMON_KEEPER_EN;
+		I915_WRITE(ICL_PORT_PCS_DW1_AUX(port), tmp);
+	}
+
+	/*
+	 * Set SUS Clock Config bitfield to 11b
+	 * Note: loadgen select program is done
+	 * as part of lane phy sequence configuration
+	 */
+	for_each_dsi_port(port, intel_dsi->ports) {
+		tmp = I915_READ(ICL_PORT_CL_DW5(port));
+		tmp |= SUS_CLOCK_CONFIG;
+		I915_WRITE(ICL_PORT_CL_DW5(port), tmp);
+	}
+
+	/* Clear training enable to change swing values */
+	for_each_dsi_port(port, intel_dsi->ports) {
+		tmp = I915_READ(ICL_PORT_TX_DW5_LN0(port));
+		tmp &= ~TX_TRAINING_EN;
+		I915_WRITE(ICL_PORT_TX_DW5_GRP(port), tmp);
+		tmp = I915_READ(ICL_PORT_TX_DW5_AUX(port));
+		tmp &= ~TX_TRAINING_EN;
+		I915_WRITE(ICL_PORT_TX_DW5_AUX(port), tmp);
+	}
+
+	/* Program swing and de-emphasis */
+	dsi_program_swing_and_deemphasis(encoder);
+
+	/* Set training enable to trigger update */
+	for_each_dsi_port(port, intel_dsi->ports) {
+		tmp = I915_READ(ICL_PORT_TX_DW5_LN0(port));
+		tmp |= TX_TRAINING_EN;
+		I915_WRITE(ICL_PORT_TX_DW5_GRP(port), tmp);
+		tmp = I915_READ(ICL_PORT_TX_DW5_AUX(port));
+		tmp |= TX_TRAINING_EN;
+		I915_WRITE(ICL_PORT_TX_DW5_AUX(port), tmp);
+	}
+}
+
 static void gen11_dsi_enable_port_and_phy(struct intel_encoder *encoder)
 {
 	/* step 4a: power up all lanes of the DDI used by DSI */
@@ -148,6 +265,9 @@ static void gen11_dsi_enable_port_and_phy(struct intel_encoder *encoder)
 
 	/* step 4b: configure lane sequencing of the Combo-PHY transmitters */
 	gen11_dsi_config_phy_lanes_sequence(encoder);
+
+	/* step 4c: configure voltage swing and skew */
+	gen11_dsi_voltage_swing_program_seq(encoder);
 }
 
 static void __attribute__((unused))