drm: bridge: samsung-dsim: Implement support for clock/data polarity swap

Implement support for DSI clock and data lane DN/DP polarity swap by
means of decoding 'lane-polarities' DT property. The controller does
support DN/DP swap of clock lane and all data lanes, the controller
does not support polarity swap of individual data lane bundles, add
a check which verifies all data lanes have the same polarity.

This has been validated on an imx8mm board that actually has the MIPI DSI
clock lanes inverted.
Signed-off-by: Marek Vasut <marex@denx.de>
Signed-off-by: Fabio Estevam <festevam@denx.de>
Reviewed-by: Jagan Teki <jagan@amarulasolutions.com>
Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20230514114625.98372-2-festevam@gmail.com

drivers/gpu/drm/bridge/samsung-dsim.c

@@ -183,6 +183,8 @@
 #define DSIM_AFC_CTL(x)			(((x) & 0x7) << 5)
 
 /* DSIM_PLLCTRL */
+#define DSIM_PLL_DPDNSWAP_CLK		(1 << 25)
+#define DSIM_PLL_DPDNSWAP_DAT		(1 << 24)
 #define DSIM_FREQ_BAND(x)		((x) << 24)
 #define DSIM_PLL_EN			BIT(23)
 #define DSIM_PLL_P(x, offset)		((x) << (offset))
@@ -622,6 +624,11 @@ static unsigned long samsung_dsim_set_pll(struct samsung_dsim *dsi,
 		reg |= DSIM_FREQ_BAND(band);
 	}
 
+	if (dsi->swap_dn_dp_clk)
+		reg |= DSIM_PLL_DPDNSWAP_CLK;
+	if (dsi->swap_dn_dp_data)
+		reg |= DSIM_PLL_DPDNSWAP_DAT;
+
 	samsung_dsim_write(dsi, DSIM_PLLCTRL_REG, reg);
 
 	timeout = 1000;
@@ -1696,7 +1703,9 @@ static int samsung_dsim_parse_dt(struct samsung_dsim *dsi)
 {
 	struct device *dev = dsi->dev;
 	struct device_node *node = dev->of_node;
-	int ret;
+	u32 lane_polarities[5] = { 0 };
+	struct device_node *endpoint;
+	int i, nr_lanes, ret;
 
 	ret = samsung_dsim_of_read_u32(node, "samsung,pll-clock-frequency",
 				       &dsi->pll_clk_rate);
@@ -1713,6 +1722,22 @@ static int samsung_dsim_parse_dt(struct samsung_dsim *dsi)
 	if (ret < 0)
 		return ret;
 
+	endpoint = of_graph_get_endpoint_by_regs(node, 1, -1);
+	nr_lanes = of_property_count_u32_elems(endpoint, "data-lanes");
+	if (nr_lanes > 0 && nr_lanes <= 4) {
+		/* Polarity 0 is clock lane, 1..4 are data lanes. */
+		of_property_read_u32_array(endpoint, "lane-polarities",
+					   lane_polarities, nr_lanes + 1);
+		for (i = 1; i <= nr_lanes; i++) {
+			if (lane_polarities[1] != lane_polarities[i])
+				DRM_DEV_ERROR(dsi->dev, "Data lanes polarities do not match");
+		}
+		if (lane_polarities[0])
+			dsi->swap_dn_dp_clk = true;
+		if (lane_polarities[1])
+			dsi->swap_dn_dp_data = true;
+	}
+
 	return 0;
 }
 

include/drm/bridge/samsung-dsim.h

@@ -95,6 +95,8 @@ struct samsung_dsim {
 	u32 mode_flags;
 	u32 format;
 
+	bool swap_dn_dp_clk;
+	bool swap_dn_dp_data;
 	int state;
 	struct drm_property *brightness;
 	struct completion completed;