drm/tegra: hub: Enable all required clocks

The display architecture on Tegra186 and Tegra194 requires that there be
some valid clock on all domains before accessing any display register. A
further requirement is that in addition to the host1x, hub, disp and dsc
clocks, all the head clocks (pclk0-2 on Tegra186 or pclk0-3 on Tegra194)
must also be enabled.

Implement this logic within the display hub driver to ensure the clocks
are always enabled at the right time.
Signed-off-by: Thierry Reding <treding@nvidia.com>

drivers/gpu/drm/tegra/hub.c

@@ -742,7 +742,9 @@ static const struct host1x_client_ops tegra_display_hub_ops = {
 
 static int tegra_display_hub_probe(struct platform_device *pdev)
 {
+	struct device_node *child = NULL;
 	struct tegra_display_hub *hub;
+	struct clk *clk;
 	unsigned int i;
 	int err;
 
@@ -801,6 +803,34 @@ static int tegra_display_hub_probe(struct platform_device *pdev)
 			return err;
 	}
 
+	hub->num_heads = of_get_child_count(pdev->dev.of_node);
+
+	hub->clk_heads = devm_kcalloc(&pdev->dev, hub->num_heads, sizeof(clk),
+				      GFP_KERNEL);
+	if (!hub->clk_heads)
+		return -ENOMEM;
+
+	for (i = 0; i < hub->num_heads; i++) {
+		child = of_get_next_child(pdev->dev.of_node, child);
+		if (!child) {
+			dev_err(&pdev->dev, "failed to find node for head %u\n",
+				i);
+			return -ENODEV;
+		}
+
+		clk = devm_get_clk_from_child(&pdev->dev, child, "dc");
+		if (IS_ERR(clk)) {
+			dev_err(&pdev->dev, "failed to get clock for head %u\n",
+				i);
+			of_node_put(child);
+			return PTR_ERR(clk);
+		}
+
+		hub->clk_heads[i] = clk;
+	}
+
+	of_node_put(child);
+
 	/* XXX: enable clock across reset? */
 	err = reset_control_assert(hub->rst);
 	if (err < 0)
@@ -840,12 +870,16 @@ static int tegra_display_hub_remove(struct platform_device *pdev)
 static int __maybe_unused tegra_display_hub_suspend(struct device *dev)
 {
 	struct tegra_display_hub *hub = dev_get_drvdata(dev);
+	unsigned int i = hub->num_heads;
 	int err;
 
 	err = reset_control_assert(hub->rst);
 	if (err < 0)
 		return err;
 
+	while (i--)
+		clk_disable_unprepare(hub->clk_heads[i]);
+
 	clk_disable_unprepare(hub->clk_hub);
 	clk_disable_unprepare(hub->clk_dsc);
 	clk_disable_unprepare(hub->clk_disp);
@@ -856,6 +890,7 @@ static int __maybe_unused tegra_display_hub_suspend(struct device *dev)
 static int __maybe_unused tegra_display_hub_resume(struct device *dev)
 {
 	struct tegra_display_hub *hub = dev_get_drvdata(dev);
+	unsigned int i;
 	int err;
 
 	err = clk_prepare_enable(hub->clk_disp);
@@ -870,13 +905,22 @@ static int __maybe_unused tegra_display_hub_resume(struct device *dev)
 	if (err < 0)
 		goto disable_dsc;
 
+	for (i = 0; i < hub->num_heads; i++) {
+		err = clk_prepare_enable(hub->clk_heads[i]);
+		if (err < 0)
+			goto disable_heads;
+	}
+
 	err = reset_control_deassert(hub->rst);
 	if (err < 0)
-		goto disable_hub;
+		goto disable_heads;
 
 	return 0;
 
-disable_hub:
+disable_heads:
+	while (i--)
+		clk_disable_unprepare(hub->clk_heads[i]);
+
 	clk_disable_unprepare(hub->clk_hub);
 disable_dsc:
 	clk_disable_unprepare(hub->clk_dsc);

drivers/gpu/drm/tegra/hub.h

@@ -49,6 +49,9 @@ struct tegra_display_hub {
 	struct clk *clk_hub;
 	struct reset_control *rst;
 
+	unsigned int num_heads;
+	struct clk **clk_heads;
+
 	const struct tegra_display_hub_soc *soc;
 	struct tegra_windowgroup *wgrps;
 };