drm/i915/icl: Power down unused DSI lanes

To save power, unused lanes should be powered
down using the bitfield of PORT_CL_DW10.

v2: Review comments from Jani N
    - Put default label next to case 4
    - Include the shifts in the macros

Signed-off-by: Madhav Chauhan <madhav.chauhan@intel.com>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/1530798591-2077-7-git-send-email-madhav.chauhan@intel.com

drivers/gpu/drm/i915/icl_dsi.c

@@ -74,6 +74,43 @@ static void gen11_dsi_enable_io_power(struct intel_encoder *encoder)
 	}
 }
 
+static void gen11_dsi_power_up_lanes(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;
+	u32 lane_mask;
+
+	switch (intel_dsi->lane_count) {
+	case 1:
+		lane_mask = PWR_DOWN_LN_3_1_0;
+		break;
+	case 2:
+		lane_mask = PWR_DOWN_LN_3_1;
+		break;
+	case 3:
+		lane_mask = PWR_DOWN_LN_3;
+		break;
+	case 4:
+	default:
+		lane_mask = PWR_UP_ALL_LANES;
+		break;
+	}
+
+	for_each_dsi_port(port, intel_dsi->ports) {
+		tmp = I915_READ(ICL_PORT_CL_DW10(port));
+		tmp &= ~PWR_DOWN_LN_MASK;
+		I915_WRITE(ICL_PORT_CL_DW10(port), tmp | lane_mask);
+	}
+}
+
+static void gen11_dsi_enable_port_and_phy(struct intel_encoder *encoder)
+{
+	/* step 4a: power up all lanes of the DDI used by DSI */
+	gen11_dsi_power_up_lanes(encoder);
+}
+
 static void __attribute__((unused))
 gen11_dsi_pre_enable(struct intel_encoder *encoder,
 		     const struct intel_crtc_state *pipe_config,
@@ -84,4 +121,7 @@ gen11_dsi_pre_enable(struct intel_encoder *encoder,
 
 	/* step3: enable DSI PLL */
 	gen11_dsi_program_esc_clk_div(encoder);
+
+	/* step4: enable DSI port and DPHY */
+	gen11_dsi_enable_port_and_phy(encoder);
 }