[PATCH] drm/tegra: gr3d: fix autosuspend cleanup during teardown

[PATCH] drm/tegra: gr3d: fix autosuspend cleanup during teardown

[Guangshuo Li]

gr3d_probe() calls pm_runtime_use_autosuspend(), but gr3d_remove()
does not call the matching pm_runtime_dont_use_autosuspend() during
teardown.

If the autosuspend delay is set to a negative value while autosuspend
is enabled, the runtime PM core increments usage_count to prevent
runtime suspend. Without calling pm_runtime_dont_use_autosuspend()
during teardown, this reference is not dropped.

The documentation for pm_runtime_use_autosuspend() also notes that it
is important to undo it with pm_runtime_dont_use_autosuspend() at
driver exit time, unless runtime PM was initially enabled with
devm_pm_runtime_enable().

Add the missing pm_runtime_dont_use_autosuspend() call to the driver
remove path.

This issue was found by manual code inspection.

Fixes: 62fa0a985e2c ("drm/tegra: Enable runtime PM during probe")
Cc: stable@vger.kernel.org
Signed-off-by: Guangshuo Li <lgs201920130244@gmail.com>
---
 drivers/gpu/drm/tegra/gr3d.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/gpu/drm/tegra/gr3d.c b/drivers/gpu/drm/tegra/gr3d.c
index 1ec6ced959e4..5fd1fd32fcc0 100644
--- a/drivers/gpu/drm/tegra/gr3d.c
+++ b/drivers/gpu/drm/tegra/gr3d.c
@@ -534,6 +534,7 @@ static void gr3d_remove(struct platform_device *pdev)
 {
 	struct gr3d *gr3d = platform_get_drvdata(pdev);
 
+	pm_runtime_dont_use_autosuspend(&pdev->dev);
 	pm_runtime_disable(&pdev->dev);
 	host1x_client_unregister(&gr3d->client.base);
 }
-- 
2.43.0

Re: [PATCH] drm/tegra: gr3d: fix autosuspend cleanup during teardown

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 2 potential issue(s) to consider:

Pre-existing issues:
- [High] Unreachable Code / Broken Power Management due to incorrect placement of pm_runtime_enable()
- [Medium] Guideline Violation: missing pm_ptr() wrapper for dev_pm_ops assignment
--

--- Patch [1]: [PATCH] drm/tegra: gr3d: fix autosuspend cleanup during teardown ---
commit 94bf3f52211b3cc132d2cfe856cc599ac46c8751
Author: Guangshuo Li <lgs201920130244@gmail.com>

drm/tegra: gr3d: fix autosuspend cleanup during teardown

This commit adds a missing pm_runtime_dont_use_autosuspend() call during
driver removal.

> gr3d_probe() calls pm_runtime_use_autosuspend(), but gr3d_remove()
> does not call the matching pm_runtime_dont_use_autosuspend() during
> teardown.

[Severity: High]
This is a pre-existing issue, but does the runtime PM initialization
actually work as described?

It appears pm_runtime_enable() and autosuspend configurations are placed in
gr3d_runtime_resume() rather than gr3d_probe():

drivers/gpu/drm/tegra/gr3d.c:gr3d_runtime_resume() {
        ...
        pm_runtime_enable(dev);
        pm_runtime_use_autosuspend(dev);
        pm_runtime_set_autosuspend_delay(dev, 500);
        ...
}

Since the PM core initializes devices with runtime PM disabled, won't this
callback never be invoked, leaving the device permanently in RPM_SUSPENDED
from the PM core's perspective? Should these initialization calls be moved
to gr3d_probe()?

> diff --git a/drivers/gpu/drm/tegra/gr3d.c b/drivers/gpu/drm/tegra/gr3d.c
> index 42e9656ab80c9..518bd21f52e2d 100644
> --- a/drivers/gpu/drm/tegra/gr3d.c
> +++ b/drivers/gpu/drm/tegra/gr3d.c
> @@ -524,6 +524,7 @@ static void gr3d_remove(struct platform_device *pdev)
>  {
>  	struct gr3d *gr3d = platform_get_drvdata(pdev);
>  
> +	pm_runtime_dont_use_autosuspend(&pdev->dev);
>  	pm_runtime_disable(&pdev->dev);
>  	host1x_client_unregister(&gr3d->client.base);
>  }

[Severity: Medium]
This is a pre-existing issue, but when CONFIG_PM is disabled, does
unconditionally assigning the dev_pm_ops structure create dead code?

drivers/gpu/drm/tegra/gr3d.c:tegra_gr3d_driver {
        ...
        .pm = &tegra_gr3d_pm,
        ...
}

Should this use the pm_ptr() wrapper like .pm = pm_ptr(&tegra_gr3d_pm) to
ensure the callback functions do not get linked into the kernel when they can
never execute?

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260808142217.2893936-1-lgs201920130244@gmail.com?part=1