drm/omap: improve DPI clock selection on DRA7xx

The clock source selection for the LCD outputs is too hardcoded at the
moment. For example, LCD3 is set to use PLL2_1, and PLL2 doesn't exist
on DRA72x SoCs.

There are quite many ways to configure the clocks, even using HDMI PLL
for LCD outputs, but enabling full configuration of the clocks is rather
tricky.

This patch improves the situation a bit by checking if the PLL about to
be used exists, and if not, tries another one.
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>

drivers/gpu/drm/omapdrm/dss/dpi.c

@@ -67,6 +67,45 @@ static struct dpi_data *dpi_get_data_from_pdev(struct platform_device *pdev)
 	return dev_get_drvdata(&pdev->dev);
 }
 
+static enum dss_clk_source dpi_get_clk_src_dra7xx(enum omap_channel channel)
+{
+	/*
+	 * Possible clock sources:
+	 * LCD1: FCK/PLL1_1/HDMI_PLL
+	 * LCD2: FCK/PLL1_3/HDMI_PLL (DRA74x: PLL2_3)
+	 * LCD3: FCK/PLL1_3/HDMI_PLL (DRA74x: PLL2_1)
+	 */
+
+	switch (channel) {
+	case OMAP_DSS_CHANNEL_LCD:
+	{
+		if (dss_pll_find_by_src(DSS_CLK_SRC_PLL1_1))
+			return DSS_CLK_SRC_PLL1_1;
+		break;
+	}
+	case OMAP_DSS_CHANNEL_LCD2:
+	{
+		if (dss_pll_find_by_src(DSS_CLK_SRC_PLL1_3))
+			return DSS_CLK_SRC_PLL1_3;
+		if (dss_pll_find_by_src(DSS_CLK_SRC_PLL2_3))
+			return DSS_CLK_SRC_PLL2_3;
+		break;
+	}
+	case OMAP_DSS_CHANNEL_LCD3:
+	{
+		if (dss_pll_find_by_src(DSS_CLK_SRC_PLL2_1))
+			return DSS_CLK_SRC_PLL2_1;
+		if (dss_pll_find_by_src(DSS_CLK_SRC_PLL1_3))
+			return DSS_CLK_SRC_PLL1_3;
+		break;
+	}
+	default:
+		break;
+	}
+
+	return DSS_CLK_SRC_FCK;
+}
+
 static enum dss_clk_source dpi_get_clk_src(enum omap_channel channel)
 {
 	/*
@@ -107,16 +146,7 @@ static enum dss_clk_source dpi_get_clk_src(enum omap_channel channel)
 		}
 
 	case OMAPDSS_VER_DRA7xx:
-		switch (channel) {
-		case OMAP_DSS_CHANNEL_LCD:
-			return DSS_CLK_SRC_PLL1_1;
-		case OMAP_DSS_CHANNEL_LCD2:
-			return DSS_CLK_SRC_PLL1_3;
-		case OMAP_DSS_CHANNEL_LCD3:
-			return DSS_CLK_SRC_PLL2_1;
-		default:
-			return DSS_CLK_SRC_FCK;
-		}
+		return dpi_get_clk_src_dra7xx(channel);
 
 	default:
 		return DSS_CLK_SRC_FCK;