drm/bridge: ti-sn65dsi86: Don't use MIPI variables for DP link

The ti-sn65dsi86 is a bridge from MIPI to DP and thus has two links:
the MIPI link and the DP link.  The two links do not need to have the
same format or number of lanes.  Stop using MIPI variables when
talking about the DP link.

This has zero functional change because:
* currently we are hardcoding the MIPI link as unpacked RGB888 which
  requires 24 bits and currently we are not changing the DP link rate
  from the bridge's default of 8 bits per pixel.
* currently we are hardcoding both the MIPI and DP as being 4 lanes.

This is all in prep for fixing some of the above.
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Tested-by: Rob Clark <robdclark@gmail.com>
Reviewed-by: Rob Clark <robdclark@gmail.com>
Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191218143416.v3.3.Ia6e05f4961adb0d4a0d32ba769dd7781ee8db431@changeid

drivers/gpu/drm/bridge/ti-sn65dsi86.c

@@ -100,6 +100,7 @@ struct ti_sn_bridge {
 	struct drm_panel		*panel;
 	struct gpio_desc		*enable_gpio;
 	struct regulator_bulk_data	supplies[SN_REGULATOR_SUPPLY_NUM];
+	int				dp_lanes;
 };
 
 static const struct regmap_range ti_sn_bridge_volatile_ranges[] = {
@@ -313,6 +314,7 @@ static int ti_sn_bridge_attach(struct drm_bridge *bridge)
 	}
 
 	/* TODO: setting to 4 lanes always for now */
+	pdata->dp_lanes = 4;
 	dsi->lanes = 4;
 	dsi->format = MIPI_DSI_FMT_RGB888;
 	dsi->mode_flags = MIPI_DSI_MODE_VIDEO;
@@ -451,13 +453,17 @@ static void ti_sn_bridge_set_dp_rate(struct ti_sn_bridge *pdata)
 	struct drm_display_mode *mode =
 		&pdata->bridge.encoder->crtc->state->adjusted_mode;
 
-	/* set DSIA clk frequency */
-	bit_rate_mhz = (mode->clock / 1000) *
-			mipi_dsi_pixel_format_to_bpp(pdata->dsi->format);
+	/*
+	 * Calculate minimum bit rate based on our pixel clock.  At
+	 * the moment this driver never sets the DP_18BPP_EN bit in
+	 * register 0x5b so we hardcode 24bpp.
+	 */
+	bit_rate_mhz = (mode->clock / 1000) * 24;
 
-	/* set DP data rate */
-	dp_rate_mhz = ((bit_rate_mhz / pdata->dsi->lanes) * DP_CLK_FUDGE_NUM) /
+	/* Calculate minimum DP data rate, taking 80% as per DP spec */
+	dp_rate_mhz = ((bit_rate_mhz / pdata->dp_lanes) * DP_CLK_FUDGE_NUM) /
 							DP_CLK_FUDGE_DEN;
+
 	for (i = 1; i < ARRAY_SIZE(ti_sn_bridge_dp_rate_lut) - 1; i++)
 		if (ti_sn_bridge_dp_rate_lut[i] > dp_rate_mhz)
 			break;
@@ -517,7 +523,7 @@ static void ti_sn_bridge_enable(struct drm_bridge *bridge)
 			   CHA_DSI_LANES_MASK, val);
 
 	/* DP lane config */
-	val = DP_NUM_LANES(pdata->dsi->lanes - 1);
+	val = DP_NUM_LANES(pdata->dp_lanes - 1);
 	regmap_update_bits(pdata->regmap, SN_SSC_CONFIG_REG, DP_NUM_LANES_MASK,
 			   val);