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, 88 insertions, 66 deletions

diff --git a/drivers/gpu/drm/tegra/sor.c b/drivers/gpu/drm/tegra/sor.c
index 956bf5d680ad..200d99e17afe 100644
--- a/drivers/gpu/drm/tegra/sor.c
+++ b/drivers/gpu/drm/tegra/sor.c
@@ -2255,7 +2255,7 @@ static void tegra_sor_hdmi_disable(struct drm_encoder *encoder)
 	if (err < 0)
 		dev_err(sor->dev, "failed to power off I/O pad: %d\n", err);
 
-	pm_runtime_put(sor->dev);
+	host1x_client_suspend(&sor->client);
 }
 
 static void tegra_sor_hdmi_enable(struct drm_encoder *encoder)
@@ -2276,7 +2276,11 @@ static void tegra_sor_hdmi_enable(struct drm_encoder *encoder)
 	mode = &encoder->crtc->state->adjusted_mode;
 	pclk = mode->clock * 1000;
 
-	pm_runtime_get_sync(sor->dev);
+	err = host1x_client_resume(&sor->client);
+	if (err < 0) {
+		dev_err(sor->dev, "failed to resume: %d\n", err);
+		return;
+	}
 
 	/* switch to safe parent clock */
 	err = tegra_sor_set_parent_clock(sor, sor->clk_safe);
@@ -2722,7 +2726,7 @@ static void tegra_sor_dp_disable(struct drm_encoder *encoder)
 	if (output->panel)
 		drm_panel_unprepare(output->panel);
 
-	pm_runtime_put(sor->dev);
+	host1x_client_suspend(&sor->client);
 }
 
 static void tegra_sor_dp_enable(struct drm_encoder *encoder)
@@ -2742,7 +2746,11 @@ static void tegra_sor_dp_enable(struct drm_encoder *encoder)
 	mode = &encoder->crtc->state->adjusted_mode;
 	info = &output->connector.display_info;
 
-	pm_runtime_get_sync(sor->dev);
+	err = host1x_client_resume(&sor->client);
+	if (err < 0) {
+		dev_err(sor->dev, "failed to resume: %d\n", err);
+		return;
+	}
 
 	/* switch to safe parent clock */
 	err = tegra_sor_set_parent_clock(sor, sor->clk_safe);
@@ -3189,9 +3197,80 @@ static int tegra_sor_exit(struct host1x_client *client)
 	return 0;
 }
 
+static int tegra_sor_runtime_suspend(struct host1x_client *client)
+{
+	struct tegra_sor *sor = host1x_client_to_sor(client);
+	struct device *dev = client->dev;
+	int err;
+
+	if (sor->rst) {
+		err = reset_control_assert(sor->rst);
+		if (err < 0) {
+			dev_err(dev, "failed to assert reset: %d\n", err);
+			return err;
+		}
+
+		reset_control_release(sor->rst);
+	}
+
+	usleep_range(1000, 2000);
+
+	clk_disable_unprepare(sor->clk);
+	pm_runtime_put_sync(dev);
+
+	return 0;
+}
+
+static int tegra_sor_runtime_resume(struct host1x_client *client)
+{
+	struct tegra_sor *sor = host1x_client_to_sor(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(sor->clk);
+	if (err < 0) {
+		dev_err(dev, "failed to enable clock: %d\n", err);
+		goto put_rpm;
+	}
+
+	usleep_range(1000, 2000);
+
+	if (sor->rst) {
+		err = reset_control_acquire(sor->rst);
+		if (err < 0) {
+			dev_err(dev, "failed to acquire reset: %d\n", err);
+			goto disable_clk;
+		}
+
+		err = reset_control_deassert(sor->rst);
+		if (err < 0) {
+			dev_err(dev, "failed to deassert reset: %d\n", err);
+			goto release_reset;
+		}
+	}
+
+	return 0;
+
+release_reset:
+	reset_control_release(sor->rst);
+disable_clk:
+	clk_disable_unprepare(sor->clk);
+put_rpm:
+	pm_runtime_put_sync(dev);
+	return err;
+}
+
 static const struct host1x_client_ops sor_client_ops = {
 	.init = tegra_sor_init,
 	.exit = tegra_sor_exit,
+	.suspend = tegra_sor_runtime_suspend,
+	.resume = tegra_sor_runtime_resume,
 };
 
 static const u8 tegra124_sor_xbar_cfg[5] = {
@@ -3842,10 +3921,9 @@ static int tegra_sor_probe(struct platform_device *pdev)
 	if (!sor->clk_pad) {
 		char *name;
 
-		err = pm_runtime_get_sync(&pdev->dev);
+		err = host1x_client_resume(&sor->client);
 		if (err < 0) {
-			dev_err(&pdev->dev, "failed to get runtime PM: %d\n",
-				err);
+			dev_err(sor->dev, "failed to resume: %d\n", err);
 			goto remove;
 		}
 
@@ -3856,7 +3934,7 @@ static int tegra_sor_probe(struct platform_device *pdev)
 		}
 
 		sor->clk_pad = tegra_clk_sor_pad_register(sor, name);
-		pm_runtime_put(&pdev->dev);
+		host1x_client_suspend(&sor->client);
 	}
 
 	if (IS_ERR(sor->clk_pad)) {
@@ -3912,61 +3990,6 @@ static int tegra_sor_remove(struct platform_device *pdev)
 	return 0;
 }
 
-static int tegra_sor_runtime_suspend(struct device *dev)
-{
-	struct tegra_sor *sor = dev_get_drvdata(dev);
-	int err;
-
-	if (sor->rst) {
-		err = reset_control_assert(sor->rst);
-		if (err < 0) {
-			dev_err(dev, "failed to assert reset: %d\n", err);
-			return err;
-		}
-
-		reset_control_release(sor->rst);
-	}
-
-	usleep_range(1000, 2000);
-
-	clk_disable_unprepare(sor->clk);
-
-	return 0;
-}
-
-static int tegra_sor_runtime_resume(struct device *dev)
-{
-	struct tegra_sor *sor = dev_get_drvdata(dev);
-	int err;
-
-	err = clk_prepare_enable(sor->clk);
-	if (err < 0) {
-		dev_err(dev, "failed to enable clock: %d\n", err);
-		return err;
-	}
-
-	usleep_range(1000, 2000);
-
-	if (sor->rst) {
-		err = reset_control_acquire(sor->rst);
-		if (err < 0) {
-			dev_err(dev, "failed to acquire reset: %d\n", err);
-			clk_disable_unprepare(sor->clk);
-			return err;
-		}
-
-		err = reset_control_deassert(sor->rst);
-		if (err < 0) {
-			dev_err(dev, "failed to deassert reset: %d\n", err);
-			reset_control_release(sor->rst);
-			clk_disable_unprepare(sor->clk);
-			return err;
-		}
-	}
-
-	return 0;
-}
-
 static int tegra_sor_suspend(struct device *dev)
 {
 	struct tegra_sor *sor = dev_get_drvdata(dev);
@@ -3974,8 +3997,9 @@ static int tegra_sor_suspend(struct device *dev)
 
 	if (sor->hdmi_supply) {
 		err = regulator_disable(sor->hdmi_supply);
-		if (err < 0)
+		if (err < 0) {
 			return err;
+		}
 	}
 
 	return 0;
@@ -3996,8 +4020,6 @@ static int tegra_sor_resume(struct device *dev)
 }
 
 static const struct dev_pm_ops tegra_sor_pm_ops = {
-	SET_RUNTIME_PM_OPS(tegra_sor_runtime_suspend, tegra_sor_runtime_resume,
-			   NULL)
 	SET_SYSTEM_SLEEP_PM_OPS(tegra_sor_suspend, tegra_sor_resume)
 };