drm/bridge: dw-mipi-dsi: permit configuring the escape clock rate

The Amlogic D-PHY in the Amlogic AXG SoC Family does support a frequency
higher than 10MHz for the TX Escape Clock, thus make the target rate
configurable.
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Reviewed-by: Philippe Cornu <philippe.cornu@st.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200904125531.15248-1-narmstrong@baylibre.com

drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c

@@ -605,15 +605,30 @@ static void dw_mipi_dsi_disable(struct dw_mipi_dsi *dsi)
 
 static void dw_mipi_dsi_init(struct dw_mipi_dsi *dsi)
 {
+	const struct dw_mipi_dsi_phy_ops *phy_ops = dsi->plat_data->phy_ops;
+	unsigned int esc_rate; /* in MHz */
+	u32 esc_clk_division;
+	int ret;
+
 	/*
 	 * The maximum permitted escape clock is 20MHz and it is derived from
-	 * lanebyteclk, which is running at "lane_mbps / 8".  Thus we want:
-	 *
-	 *     (lane_mbps >> 3) / esc_clk_division < 20
+	 * lanebyteclk, which is running at "lane_mbps / 8".
+	 */
+	if (phy_ops->get_esc_clk_rate) {
+		ret = phy_ops->get_esc_clk_rate(dsi->plat_data->priv_data,
+						&esc_rate);
+		if (ret)
+			DRM_DEBUG_DRIVER("Phy get_esc_clk_rate() failed\n");
+	} else
+		esc_rate = 20; /* Default to 20MHz */
+
+	/*
+	 * We want :
+	 *     (lane_mbps >> 3) / esc_clk_division < X
 	 * which is:
-	 *     (lane_mbps >> 3) / 20 > esc_clk_division
+	 *     (lane_mbps >> 3) / X > esc_clk_division
 	 */
-	u32 esc_clk_division = (dsi->lane_mbps >> 3) / 20 + 1;
+	esc_clk_division = (dsi->lane_mbps >> 3) / esc_rate + 1;
 
 	dsi_write(dsi, DSI_PWR_UP, RESET);
 

include/drm/bridge/dw_mipi_dsi.h

@@ -36,6 +36,7 @@ struct dw_mipi_dsi_phy_ops {
 			     unsigned int *lane_mbps);
 	int (*get_timing)(void *priv_data, unsigned int lane_mbps,
 			  struct dw_mipi_dsi_dphy_timing *timing);
+	int (*get_esc_clk_rate)(void *priv_data, unsigned int *esc_clk_rate);
 };
 
 struct dw_mipi_dsi_host_ops {