Re: [PATCH v2 1/2] drm/tegra: hub: Enable all required clocks

[Dmitry Osipenko <digetx@xxxxxxxxx>]

On 29.11.2018 19:24, Thierry Reding wrote:
> From: Thierry Reding <treding@xxxxxxxxxx>
> 
> 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@xxxxxxxxxx>
> ---
> Changes in v2:
> - reverse order in which clocks are disabled for symmetry
> - don't leak child device tree node
> 

And here is a variant that uses bulk-API, it looks nicer to me. Don't you think so?

diff --git a/drivers/gpu/drm/tegra/hub.c b/drivers/gpu/drm/tegra/hub.c
index 6112d9042979..d597de7d0de4 100644
--- a/drivers/gpu/drm/tegra/hub.c
+++ b/drivers/gpu/drm/tegra/hub.c
@@ -742,6 +742,7 @@ 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;
 	unsigned int i;
 	int err;
@@ -801,6 +802,29 @@ 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(*hub->clk_heads), 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);
+
+		hub->clk_heads[i].id = "dc";
+		hub->clk_heads[i].clk = devm_get_clk_from_child(&pdev->dev,
+								child, "dc");
+		if (IS_ERR(hub->clk_heads[i].clk)) {
+			dev_err(&pdev->dev, "failed to get clock for head %u\n",
+				i);
+			of_node_put(child);
+			return PTR_ERR(hub->clk_heads[i].clk);
+		}
+	}
+
+	of_node_put(child);
+
 	/* XXX: enable clock across reset? */
 	err = reset_control_assert(hub->rst);
 	if (err < 0)
@@ -846,6 +870,7 @@ static int __maybe_unused tegra_display_hub_suspend(struct device *dev)
 	if (err < 0)
 		return err;
 
+	clk_bulk_disable_unprepare(hub->num_heads, hub->clk_heads);
 	clk_disable_unprepare(hub->clk_hub);
 	clk_disable_unprepare(hub->clk_dsc);
 	clk_disable_unprepare(hub->clk_disp);
@@ -870,12 +895,18 @@ static int __maybe_unused tegra_display_hub_resume(struct device *dev)
 	if (err < 0)
 		goto disable_dsc;
 
-	err = reset_control_deassert(hub->rst);
+	err = clk_bulk_prepare_enable(hub->num_heads, hub->clk_heads);
 	if (err < 0)
 		goto disable_hub;
 
+	err = reset_control_deassert(hub->rst);
+	if (err < 0)
+		goto disable_heads;
+
 	return 0;
 
+disable_heads:
+	clk_bulk_disable_unprepare(hub->num_heads, hub->clk_heads);
 disable_hub:
 	clk_disable_unprepare(hub->clk_hub);
 disable_dsc:
diff --git a/drivers/gpu/drm/tegra/hub.h b/drivers/gpu/drm/tegra/hub.h
index 6696a85fc1f2..40866765ef0d 100644
--- a/drivers/gpu/drm/tegra/hub.h
+++ b/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_bulk_data *clk_heads;
+
 	const struct tegra_display_hub_soc *soc;
 	struct tegra_windowgroup *wgrps;
 };