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, 97 insertions, 78 deletions

diff --git a/drivers/gpu/drm/tegra/dsi.c b/drivers/gpu/drm/tegra/dsi.c
index ec475d022fa0..88b9d64c77bf 100644
--- a/drivers/gpu/drm/tegra/dsi.c
+++ b/drivers/gpu/drm/tegra/dsi.c
@@ -840,7 +840,9 @@ static void tegra_dsi_unprepare(struct tegra_dsi *dsi)
 		dev_err(dsi->dev, "failed to disable MIPI calibration: %d\n",
 			err);
 
-	pm_runtime_put(dsi->dev);
+	err = host1x_client_suspend(&dsi->client);
+	if (err < 0)
+		dev_err(dsi->dev, "failed to suspend: %d\n", err);
 }
 
 static void tegra_dsi_encoder_disable(struct drm_encoder *encoder)
@@ -882,11 +884,15 @@ static void tegra_dsi_encoder_disable(struct drm_encoder *encoder)
 	tegra_dsi_unprepare(dsi);
 }
 
-static void tegra_dsi_prepare(struct tegra_dsi *dsi)
+static int tegra_dsi_prepare(struct tegra_dsi *dsi)
 {
 	int err;
 
-	pm_runtime_get_sync(dsi->dev);
+	err = host1x_client_resume(&dsi->client);
+	if (err < 0) {
+		dev_err(dsi->dev, "failed to resume: %d\n", err);
+		return err;
+	}
 
 	err = tegra_mipi_enable(dsi->mipi);
 	if (err < 0)
@@ -899,6 +905,8 @@ static void tegra_dsi_prepare(struct tegra_dsi *dsi)
 
 	if (dsi->slave)
 		tegra_dsi_prepare(dsi->slave);
+
+	return 0;
 }
 
 static void tegra_dsi_encoder_enable(struct drm_encoder *encoder)
@@ -909,8 +917,13 @@ static void tegra_dsi_encoder_enable(struct drm_encoder *encoder)
 	struct tegra_dsi *dsi = to_dsi(output);
 	struct tegra_dsi_state *state;
 	u32 value;
+	int err;
 
-	tegra_dsi_prepare(dsi);
+	err = tegra_dsi_prepare(dsi);
+	if (err < 0) {
+		dev_err(dsi->dev, "failed to prepare: %d\n", err);
+		return;
+	}
 
 	state = tegra_dsi_get_state(dsi);
 
@@ -1075,9 +1088,89 @@ static int tegra_dsi_exit(struct host1x_client *client)
 	return 0;
 }
 
+static int tegra_dsi_runtime_suspend(struct host1x_client *client)
+{
+	struct tegra_dsi *dsi = host1x_client_to_dsi(client);
+	struct device *dev = client->dev;
+	int err;
+
+	if (dsi->rst) {
+		err = reset_control_assert(dsi->rst);
+		if (err < 0) {
+			dev_err(dev, "failed to assert reset: %d\n", err);
+			return err;
+		}
+	}
+
+	usleep_range(1000, 2000);
+
+	clk_disable_unprepare(dsi->clk_lp);
+	clk_disable_unprepare(dsi->clk);
+
+	regulator_disable(dsi->vdd);
+	pm_runtime_put_sync(dev);
+
+	return 0;
+}
+
+static int tegra_dsi_runtime_resume(struct host1x_client *client)
+{
+	struct tegra_dsi *dsi = host1x_client_to_dsi(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 = regulator_enable(dsi->vdd);
+	if (err < 0) {
+		dev_err(dev, "failed to enable VDD supply: %d\n", err);
+		goto put_rpm;
+	}
+
+	err = clk_prepare_enable(dsi->clk);
+	if (err < 0) {
+		dev_err(dev, "cannot enable DSI clock: %d\n", err);
+		goto disable_vdd;
+	}
+
+	err = clk_prepare_enable(dsi->clk_lp);
+	if (err < 0) {
+		dev_err(dev, "cannot enable low-power clock: %d\n", err);
+		goto disable_clk;
+	}
+
+	usleep_range(1000, 2000);
+
+	if (dsi->rst) {
+		err = reset_control_deassert(dsi->rst);
+		if (err < 0) {
+			dev_err(dev, "cannot assert reset: %d\n", err);
+			goto disable_clk_lp;
+		}
+	}
+
+	return 0;
+
+disable_clk_lp:
+	clk_disable_unprepare(dsi->clk_lp);
+disable_clk:
+	clk_disable_unprepare(dsi->clk);
+disable_vdd:
+	regulator_disable(dsi->vdd);
+put_rpm:
+	pm_runtime_put_sync(dev);
+	return err;
+}
+
 static const struct host1x_client_ops dsi_client_ops = {
 	.init = tegra_dsi_init,
 	.exit = tegra_dsi_exit,
+	.suspend = tegra_dsi_runtime_suspend,
+	.resume = tegra_dsi_runtime_resume,
 };
 
 static int tegra_dsi_setup_clocks(struct tegra_dsi *dsi)
@@ -1596,79 +1689,6 @@ static int tegra_dsi_remove(struct platform_device *pdev)
 	return 0;
 }
 
-#ifdef CONFIG_PM
-static int tegra_dsi_suspend(struct device *dev)
-{
-	struct tegra_dsi *dsi = dev_get_drvdata(dev);
-	int err;
-
-	if (dsi->rst) {
-		err = reset_control_assert(dsi->rst);
-		if (err < 0) {
-			dev_err(dev, "failed to assert reset: %d\n", err);
-			return err;
-		}
-	}
-
-	usleep_range(1000, 2000);
-
-	clk_disable_unprepare(dsi->clk_lp);
-	clk_disable_unprepare(dsi->clk);
-
-	regulator_disable(dsi->vdd);
-
-	return 0;
-}
-
-static int tegra_dsi_resume(struct device *dev)
-{
-	struct tegra_dsi *dsi = dev_get_drvdata(dev);
-	int err;
-
-	err = regulator_enable(dsi->vdd);
-	if (err < 0) {
-		dev_err(dsi->dev, "failed to enable VDD supply: %d\n", err);
-		return err;
-	}
-
-	err = clk_prepare_enable(dsi->clk);
-	if (err < 0) {
-		dev_err(dev, "cannot enable DSI clock: %d\n", err);
-		goto disable_vdd;
-	}
-
-	err = clk_prepare_enable(dsi->clk_lp);
-	if (err < 0) {
-		dev_err(dev, "cannot enable low-power clock: %d\n", err);
-		goto disable_clk;
-	}
-
-	usleep_range(1000, 2000);
-
-	if (dsi->rst) {
-		err = reset_control_deassert(dsi->rst);
-		if (err < 0) {
-			dev_err(dev, "cannot assert reset: %d\n", err);
-			goto disable_clk_lp;
-		}
-	}
-
-	return 0;
-
-disable_clk_lp:
-	clk_disable_unprepare(dsi->clk_lp);
-disable_clk:
-	clk_disable_unprepare(dsi->clk);
-disable_vdd:
-	regulator_disable(dsi->vdd);
-	return err;
-}
-#endif
-
-static const struct dev_pm_ops tegra_dsi_pm_ops = {
-	SET_RUNTIME_PM_OPS(tegra_dsi_suspend, tegra_dsi_resume, NULL)
-};
-
 static const struct of_device_id tegra_dsi_of_match[] = {
 	{ .compatible = "nvidia,tegra210-dsi", },
 	{ .compatible = "nvidia,tegra132-dsi", },
@@ -1682,7 +1702,6 @@ struct platform_driver tegra_dsi_driver = {
 	.driver = {
 		.name = "tegra-dsi",
 		.of_match_table = tegra_dsi_of_match,
-		.pm = &tegra_dsi_pm_ops,
 	},
 	.probe = tegra_dsi_probe,
 	.remove = tegra_dsi_remove,