drm/tegra: sor: Unify clock setup for eDP, HDMI and DP

With the clocks modelled consistently across SoC generations, the clock
setup for eDP, HDMI and DP can now be unified.
Signed-off-by: Thierry Reding <treding@nvidia.com>

drivers/gpu/drm/tegra/sor.c

@@ -527,6 +527,14 @@ static const char * const tegra_clk_sor_pad_parents[2][2] = {
 	{ "pll_d2_out0", "pll_dp" },
 };
 
+/*
+ * Implementing ->set_parent() here isn't really required because the parent
+ * will be explicitly selected in the driver code via the DP_CLK_SEL mux in
+ * the SOR_CLK_CNTRL register. This is primarily for compatibility with the
+ * Tegra186 and later SoC generations where the BPMP implements this clock
+ * and doesn't expose the mux via the common clock framework.
+ */
+
 static int tegra_clk_sor_pad_set_parent(struct clk_hw *hw, u8 index)
 {
 	struct tegra_clk_sor_pad *pad = to_pad(hw);
@@ -1987,10 +1995,36 @@ static void tegra_sor_edp_enable(struct drm_encoder *encoder)
 	tegra_sor_writel(sor, 0x00000000, SOR_XBAR_POL);
 	tegra_sor_writel(sor, value, SOR_XBAR_CTRL);
 
-	/* switch to DP parent clock */
-	err = tegra_sor_set_parent_clock(sor, sor->clk_dp);
-	if (err < 0)
-		dev_err(sor->dev, "failed to set parent clock: %d\n", err);
+	/*
+	 * Switch the pad clock to the DP clock. Note that we cannot actually
+	 * do this because Tegra186 and later don't support clk_set_parent()
+	 * on the sorX_pad_clkout clocks. We already do the equivalent above
+	 * using the DP_CLK_SEL mux of the SOR_CLK_CNTRL register.
+	 */
+#if 0
+	err = clk_set_parent(sor->clk_pad, sor->clk_dp);
+	if (err < 0) {
+		dev_err(sor->dev, "failed to select pad parent clock: %d\n",
+			err);
+		return;
+	}
+#endif
+
+	/* switch the SOR clock to the pad clock */
+	err = tegra_sor_set_parent_clock(sor, sor->clk_pad);
+	if (err < 0) {
+		dev_err(sor->dev, "failed to select SOR parent clock: %d\n",
+			err);
+		return;
+	}
+
+	/* switch the output clock to the parent pixel clock */
+	err = clk_set_parent(sor->clk, sor->clk_parent);
+	if (err < 0) {
+		dev_err(sor->dev, "failed to select output parent clock: %d\n",
+			err);
+		return;
+	}
 
 	/* use DP-A protocol */
 	value = tegra_sor_readl(sor, SOR_STATE1);
@@ -2661,16 +2695,34 @@ static void tegra_sor_hdmi_enable(struct drm_encoder *encoder)
 	tegra_sor_writel(sor, 0x00000000, SOR_XBAR_POL);
 	tegra_sor_writel(sor, value, SOR_XBAR_CTRL);
 
-	/* switch to parent clock */
-	err = clk_set_parent(sor->clk, sor->clk_parent);
+	/*
+	 * Switch the pad clock to the DP clock. Note that we cannot actually
+	 * do this because Tegra186 and later don't support clk_set_parent()
+	 * on the sorX_pad_clkout clocks. We already do the equivalent above
+	 * using the DP_CLK_SEL mux of the SOR_CLK_CNTRL register.
+	 */
+#if 0
+	err = clk_set_parent(sor->clk_pad, sor->clk_dp);
 	if (err < 0) {
-		dev_err(sor->dev, "failed to set parent clock: %d\n", err);
+		dev_err(sor->dev, "failed to select pad parent clock: %d\n",
+			err);
 		return;
 	}
+#endif
 
+	/* switch the SOR clock to the pad clock */
 	err = tegra_sor_set_parent_clock(sor, sor->clk_pad);
 	if (err < 0) {
-		dev_err(sor->dev, "failed to set pad clock: %d\n", err);
+		dev_err(sor->dev, "failed to select SOR parent clock: %d\n",
+			err);
+		return;
+	}
+
+	/* switch the output clock to the parent pixel clock */
+	err = clk_set_parent(sor->clk, sor->clk_parent);
+	if (err < 0) {
+		dev_err(sor->dev, "failed to select output parent clock: %d\n",
+			err);
 		return;
 	}
 
@@ -3061,16 +3113,34 @@ static void tegra_sor_dp_enable(struct drm_encoder *encoder)
 	tegra_sor_writel(sor, 0x00000000, SOR_XBAR_POL);
 	tegra_sor_writel(sor, value, SOR_XBAR_CTRL);
 
-	/* switch to DP parent clock */
+	/*
+	 * Switch the pad clock to the DP clock. Note that we cannot actually
+	 * do this because Tegra186 and later don't support clk_set_parent()
+	 * on the sorX_pad_clkout clocks. We already do the equivalent above
+	 * using the DP_CLK_SEL mux of the SOR_CLK_CNTRL register.
+	 */
+#if 0
+	err = clk_set_parent(sor->clk_pad, sor->clk_parent);
+	if (err < 0) {
+		dev_err(sor->dev, "failed to select pad parent clock: %d\n",
+			err);
+		return;
+	}
+#endif
+
+	/* switch the SOR clock to the pad clock */
 	err = tegra_sor_set_parent_clock(sor, sor->clk_pad);
 	if (err < 0) {
-		dev_err(sor->dev, "failed to switch to pad clock: %d\n", err);
+		dev_err(sor->dev, "failed to select SOR parent clock: %d\n",
+			err);
 		return;
 	}
 
+	/* switch the output clock to the parent pixel clock */
 	err = clk_set_parent(sor->clk, sor->clk_parent);
 	if (err < 0) {
-		dev_err(sor->dev, "failed to switch to parent clock: %d\n", err);
+		dev_err(sor->dev, "failed to select output parent clock: %d\n",
+			err);
 		return;
 	}