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, 116 insertions, 78 deletions

diff --git a/drivers/gpu/drm/tegra/hub.c b/drivers/gpu/drm/tegra/hub.c
index 7d9e1309be3b..8183e617bf6b 100644
--- a/drivers/gpu/drm/tegra/hub.c
+++ b/drivers/gpu/drm/tegra/hub.c
@@ -95,17 +95,25 @@ static inline void tegra_plane_writel(struct tegra_plane *plane, u32 value,
 
 static int tegra_windowgroup_enable(struct tegra_windowgroup *wgrp)
 {
+	int err = 0;
+
 	mutex_lock(&wgrp->lock);
 
 	if (wgrp->usecount == 0) {
-		pm_runtime_get_sync(wgrp->parent);
+		err = host1x_client_resume(wgrp->parent);
+		if (err < 0) {
+			dev_err(wgrp->parent->dev, "failed to resume: %d\n", err);
+			goto unlock;
+		}
+
 		reset_control_deassert(wgrp->rst);
 	}
 
 	wgrp->usecount++;
-	mutex_unlock(&wgrp->lock);
 
-	return 0;
+unlock:
+	mutex_unlock(&wgrp->lock);
+	return err;
 }
 
 static void tegra_windowgroup_disable(struct tegra_windowgroup *wgrp)
@@ -121,7 +129,7 @@ static void tegra_windowgroup_disable(struct tegra_windowgroup *wgrp)
 			       wgrp->index);
 		}
 
-		pm_runtime_put(wgrp->parent);
+		host1x_client_suspend(wgrp->parent);
 	}
 
 	wgrp->usecount--;
@@ -379,6 +387,7 @@ static void tegra_shared_plane_atomic_disable(struct drm_plane *plane,
 	struct tegra_plane *p = to_tegra_plane(plane);
 	struct tegra_dc *dc;
 	u32 value;
+	int err;
 
 	/* rien ne va plus */
 	if (!old_state || !old_state->crtc)
@@ -386,6 +395,12 @@ static void tegra_shared_plane_atomic_disable(struct drm_plane *plane,
 
 	dc = to_tegra_dc(old_state->crtc);
 
+	err = host1x_client_resume(&dc->client);
+	if (err < 0) {
+		dev_err(dc->dev, "failed to resume: %d\n", err);
+		return;
+	}
+
 	/*
 	 * XXX Legacy helpers seem to sometimes call ->atomic_disable() even
 	 * on planes that are already disabled. Make sure we fallback to the
@@ -394,15 +409,13 @@ static void tegra_shared_plane_atomic_disable(struct drm_plane *plane,
 	if (WARN_ON(p->dc == NULL))
 		p->dc = dc;
 
-	pm_runtime_get_sync(dc->dev);
-
 	value = tegra_plane_readl(p, DC_WIN_WIN_OPTIONS);
 	value &= ~WIN_ENABLE;
 	tegra_plane_writel(p, value, DC_WIN_WIN_OPTIONS);
 
 	tegra_dc_remove_shared_plane(dc, p);
 
-	pm_runtime_put(dc->dev);
+	host1x_client_suspend(&dc->client);
 }
 
 static void tegra_shared_plane_atomic_update(struct drm_plane *plane,
@@ -415,6 +428,7 @@ static void tegra_shared_plane_atomic_update(struct drm_plane *plane,
 	struct tegra_plane *p = to_tegra_plane(plane);
 	dma_addr_t base;
 	u32 value;
+	int err;
 
 	/* rien ne va plus */
 	if (!plane->state->crtc || !plane->state->fb)
@@ -425,7 +439,11 @@ static void tegra_shared_plane_atomic_update(struct drm_plane *plane,
 		return;
 	}
 
-	pm_runtime_get_sync(dc->dev);
+	err = host1x_client_resume(&dc->client);
+	if (err < 0) {
+		dev_err(dc->dev, "failed to resume: %d\n", err);
+		return;
+	}
 
 	tegra_dc_assign_shared_plane(dc, p);
 
@@ -515,7 +533,7 @@ static void tegra_shared_plane_atomic_update(struct drm_plane *plane,
 	value &= ~CONTROL_CSC_ENABLE;
 	tegra_plane_writel(p, value, DC_WIN_WINDOW_SET_CONTROL);
 
-	pm_runtime_put(dc->dev);
+	host1x_client_suspend(&dc->client);
 }
 
 static const struct drm_plane_helper_funcs tegra_shared_plane_helper_funcs = {
@@ -551,7 +569,7 @@ struct drm_plane *tegra_shared_plane_create(struct drm_device *drm,
 	plane->base.index = index;
 
 	plane->wgrp = &hub->wgrps[wgrp];
-	plane->wgrp->parent = dc->dev;
+	plane->wgrp->parent = &dc->client;
 
 	p = &plane->base.base;
 
@@ -656,8 +674,13 @@ int tegra_display_hub_atomic_check(struct drm_device *drm,
 static void tegra_display_hub_update(struct tegra_dc *dc)
 {
 	u32 value;
+	int err;
 
-	pm_runtime_get_sync(dc->dev);
+	err = host1x_client_resume(&dc->client);
+	if (err < 0) {
+		dev_err(dc->dev, "failed to resume: %d\n", err);
+		return;
+	}
 
 	value = tegra_dc_readl(dc, DC_CMD_IHUB_COMMON_MISC_CTL);
 	value &= ~LATENCY_EVENT;
@@ -672,7 +695,7 @@ static void tegra_display_hub_update(struct tegra_dc *dc)
 	tegra_dc_writel(dc, COMMON_ACTREQ, DC_CMD_STATE_CONTROL);
 	tegra_dc_readl(dc, DC_CMD_STATE_CONTROL);
 
-	pm_runtime_put(dc->dev);
+	host1x_client_suspend(&dc->client);
 }
 
 void tegra_display_hub_atomic_commit(struct drm_device *drm,
@@ -732,9 +755,85 @@ static int tegra_display_hub_exit(struct host1x_client *client)
 	return 0;
 }
 
+static int tegra_display_hub_runtime_suspend(struct host1x_client *client)
+{
+	struct tegra_display_hub *hub = to_tegra_display_hub(client);
+	struct device *dev = client->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);
+
+	pm_runtime_put_sync(dev);
+
+	return 0;
+}
+
+static int tegra_display_hub_runtime_resume(struct host1x_client *client)
+{
+	struct tegra_display_hub *hub = to_tegra_display_hub(client);
+	struct device *dev = client->dev;
+	unsigned int i;
+	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(hub->clk_disp);
+	if (err < 0)
+		goto put_rpm;
+
+	err = clk_prepare_enable(hub->clk_dsc);
+	if (err < 0)
+		goto disable_disp;
+
+	err = clk_prepare_enable(hub->clk_hub);
+	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_heads;
+
+	return 0;
+
+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);
+disable_disp:
+	clk_disable_unprepare(hub->clk_disp);
+put_rpm:
+	pm_runtime_put_sync(dev);
+	return err;
+}
+
 static const struct host1x_client_ops tegra_display_hub_ops = {
 	.init = tegra_display_hub_init,
 	.exit = tegra_display_hub_exit,
+	.suspend = tegra_display_hub_runtime_suspend,
+	.resume = tegra_display_hub_runtime_resume,
 };
 
 static int tegra_display_hub_probe(struct platform_device *pdev)
@@ -851,6 +950,7 @@ static int tegra_display_hub_probe(struct platform_device *pdev)
 static int tegra_display_hub_remove(struct platform_device *pdev)
 {
 	struct tegra_display_hub *hub = platform_get_drvdata(pdev);
+	unsigned int i;
 	int err;
 
 	err = host1x_client_unregister(&hub->client);
@@ -859,78 +959,17 @@ static int tegra_display_hub_remove(struct platform_device *pdev)
 			err);
 	}
 
-	pm_runtime_disable(&pdev->dev);
-
-	return err;
-}
-
-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);
-
-	return 0;
-}
-
-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);
-	if (err < 0)
-		return err;
-
-	err = clk_prepare_enable(hub->clk_dsc);
-	if (err < 0)
-		goto disable_disp;
-
-	err = clk_prepare_enable(hub->clk_hub);
-	if (err < 0)
-		goto disable_dsc;
+	for (i = 0; i < hub->soc->num_wgrps; i++) {
+		struct tegra_windowgroup *wgrp = &hub->wgrps[i];
 
-	for (i = 0; i < hub->num_heads; i++) {
-		err = clk_prepare_enable(hub->clk_heads[i]);
-		if (err < 0)
-			goto disable_heads;
+		mutex_destroy(&wgrp->lock);
 	}
 
-	err = reset_control_deassert(hub->rst);
-	if (err < 0)
-		goto disable_heads;
-
-	return 0;
-
-disable_heads:
-	while (i--)
-		clk_disable_unprepare(hub->clk_heads[i]);
+	pm_runtime_disable(&pdev->dev);
 
-	clk_disable_unprepare(hub->clk_hub);
-disable_dsc:
-	clk_disable_unprepare(hub->clk_dsc);
-disable_disp:
-	clk_disable_unprepare(hub->clk_disp);
 	return err;
 }
 
-static const struct dev_pm_ops tegra_display_hub_pm_ops = {
-	SET_RUNTIME_PM_OPS(tegra_display_hub_suspend,
-			   tegra_display_hub_resume, NULL)
-};
-
 static const struct tegra_display_hub_soc tegra186_display_hub = {
 	.num_wgrps = 6,
 	.supports_dsc = true,
@@ -958,7 +997,6 @@ struct platform_driver tegra_display_hub_driver = {
 	.driver = {
 		.name = "tegra-display-hub",
 		.of_match_table = tegra_display_hub_of_match,
-		.pm = &tegra_display_hub_pm_ops,
 	},
 	.probe = tegra_display_hub_probe,
 	.remove = tegra_display_hub_remove,