drm/tegra: Do not implement runtime PM

The Tegra DRM driver heavily relies on the implementations for runtime
suspend/resume to be called at specific times. Unfortunately, there are
some cases where that doesn't work. One example is if the user disables
runtime PM for a given subdevice. Another example is that the PM core
acquires a reference to runtime PM during system sleep, effectively
preventing devices from going into low power modes. This is intentional
to avoid nasty race conditions, but it also causes system sleep to not
function properly on all Tegra systems.

Fix this by not implementing runtime PM at all. Instead, a minimal,
reference-counted suspend/resume infrastructure is added to the host1x
bus. This has the benefit that it can be used regardless of the system
power state (or any transitions we might be in), or whether or not the
user allows runtime PM.

Atomic modesetting guarantees that these functions will end up being
called at the right point in time, so the pitfalls for the more generic
runtime PM do not apply here.

Signed-off-by: Thierry Reding <treding@nvidia.com>

1 files changed, 66 insertions, 50 deletions

diff --git a/drivers/gpu/drm/tegra/hdmi.c b/drivers/gpu/drm/tegra/hdmi.c
index 38bf1d16095f..cb504ec8f284 100644
--- a/drivers/gpu/drm/tegra/hdmi.c
+++ b/drivers/gpu/drm/tegra/hdmi.c
@@ -1146,6 +1146,7 @@ static void tegra_hdmi_encoder_disable(struct drm_encoder *encoder)
 	struct tegra_dc *dc = to_tegra_dc(encoder->crtc);
 	struct tegra_hdmi *hdmi = to_hdmi(output);
 	u32 value;
+	int err;
 
 	/*
 	 * The following accesses registers of the display controller, so make
@@ -1171,7 +1172,9 @@ static void tegra_hdmi_encoder_disable(struct drm_encoder *encoder)
 	tegra_hdmi_writel(hdmi, 0, HDMI_NV_PDISP_INT_ENABLE);
 	tegra_hdmi_writel(hdmi, 0, HDMI_NV_PDISP_INT_MASK);
 
-	pm_runtime_put(hdmi->dev);
+	err = host1x_client_suspend(&hdmi->client);
+	if (err < 0)
+		dev_err(hdmi->dev, "failed to suspend: %d\n", err);
 }
 
 static void tegra_hdmi_encoder_enable(struct drm_encoder *encoder)
@@ -1186,7 +1189,11 @@ static void tegra_hdmi_encoder_enable(struct drm_encoder *encoder)
 	u32 value;
 	int err;
 
-	pm_runtime_get_sync(hdmi->dev);
+	err = host1x_client_resume(&hdmi->client);
+	if (err < 0) {
+		dev_err(hdmi->dev, "failed to resume: %d\n", err);
+		return;
+	}
 
 	/*
 	 * Enable and unmask the HDA codec SCRATCH0 register interrupt. This
@@ -1489,9 +1496,66 @@ static int tegra_hdmi_exit(struct host1x_client *client)
 	return 0;
 }
 
+static int tegra_hdmi_runtime_suspend(struct host1x_client *client)
+{
+	struct tegra_hdmi *hdmi = host1x_client_to_hdmi(client);
+	struct device *dev = client->dev;
+	int err;
+
+	err = reset_control_assert(hdmi->rst);
+	if (err < 0) {
+		dev_err(dev, "failed to assert reset: %d\n", err);
+		return err;
+	}
+
+	usleep_range(1000, 2000);
+
+	clk_disable_unprepare(hdmi->clk);
+	pm_runtime_put_sync(dev);
+
+	return 0;
+}
+
+static int tegra_hdmi_runtime_resume(struct host1x_client *client)
+{
+	struct tegra_hdmi *hdmi = host1x_client_to_hdmi(client);
+	struct device *dev = client->dev;
+	int err;
+
+	err = pm_runtime_get_sync(dev);
+	if (err < 0) {
+		dev_err(dev, "failed to get runtime PM: %d\n", err);
+		return err;
+	}
+
+	err = clk_prepare_enable(hdmi->clk);
+	if (err < 0) {
+		dev_err(dev, "failed to enable clock: %d\n", err);
+		goto put_rpm;
+	}
+
+	usleep_range(1000, 2000);
+
+	err = reset_control_deassert(hdmi->rst);
+	if (err < 0) {
+		dev_err(dev, "failed to deassert reset: %d\n", err);
+		goto disable_clk;
+	}
+
+	return 0;
+
+disable_clk:
+	clk_disable_unprepare(hdmi->clk);
+put_rpm:
+	pm_runtime_put_sync(dev);
+	return err;
+}
+
 static const struct host1x_client_ops hdmi_client_ops = {
 	.init = tegra_hdmi_init,
 	.exit = tegra_hdmi_exit,
+	.suspend = tegra_hdmi_runtime_suspend,
+	.resume = tegra_hdmi_runtime_resume,
 };
 
 static const struct tegra_hdmi_config tegra20_hdmi_config = {
@@ -1699,58 +1763,10 @@ static int tegra_hdmi_remove(struct platform_device *pdev)
 	return 0;
 }
 
-#ifdef CONFIG_PM
-static int tegra_hdmi_suspend(struct device *dev)
-{
-	struct tegra_hdmi *hdmi = dev_get_drvdata(dev);
-	int err;
-
-	err = reset_control_assert(hdmi->rst);
-	if (err < 0) {
-		dev_err(dev, "failed to assert reset: %d\n", err);
-		return err;
-	}
-
-	usleep_range(1000, 2000);
-
-	clk_disable_unprepare(hdmi->clk);
-
-	return 0;
-}
-
-static int tegra_hdmi_resume(struct device *dev)
-{
-	struct tegra_hdmi *hdmi = dev_get_drvdata(dev);
-	int err;
-
-	err = clk_prepare_enable(hdmi->clk);
-	if (err < 0) {
-		dev_err(dev, "failed to enable clock: %d\n", err);
-		return err;
-	}
-
-	usleep_range(1000, 2000);
-
-	err = reset_control_deassert(hdmi->rst);
-	if (err < 0) {
-		dev_err(dev, "failed to deassert reset: %d\n", err);
-		clk_disable_unprepare(hdmi->clk);
-		return err;
-	}
-
-	return 0;
-}
-#endif
-
-static const struct dev_pm_ops tegra_hdmi_pm_ops = {
-	SET_RUNTIME_PM_OPS(tegra_hdmi_suspend, tegra_hdmi_resume, NULL)
-};
-
 struct platform_driver tegra_hdmi_driver = {
 	.driver = {
 		.name = "tegra-hdmi",
 		.of_match_table = tegra_hdmi_of_match,
-		.pm = &tegra_hdmi_pm_ops,
 	},
 	.probe = tegra_hdmi_probe,
 	.remove = tegra_hdmi_remove,