Re: [PATCH] drm/mali-dp: Fix runtime PM leak in malidp_crtc_atomic_enable()

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [High] drm/malidp: runtime PM usage counter underflow in malidp_crtc_atomic_disable()
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commit 3492dcc2c28d3962cf4a64dc34d1fb164aaf6580
Author: Wentao Liang <vulab@iscas.ac.cn>

drm/mali-dp: Fix runtime PM leak in malidp_crtc_atomic_enable()

This patch drops the runtime PM reference with pm_runtime_put_noidle() on
the resume failure path in malidp_crtc_atomic_enable(). This is intended
to fix a reference leak when pm_runtime_get_sync() fails.

> diff --git a/drivers/gpu/drm/arm/malidp_crtc.c b/drivers/gpu/drm/arm/malidp_crtc.c
> index 157ff148efe7a..ec7b9db8b0b45 100644
> --- a/drivers/gpu/drm/arm/malidp_crtc.c
> +++ b/drivers/gpu/drm/arm/malidp_crtc.c
> @@ -56,6 +56,7 @@ static void malidp_crtc_atomic_enable(struct drm_crtc *crtc,
>  
>  	if (err < 0) {
>  		DRM_DEBUG_DRIVER("Failed to enable runtime power management: %d\n", err);
> +		pm_runtime_put_noidle(crtc->dev->dev);

[Severity: High]
Could this addition cause a runtime PM usage counter underflow when the CRTC
is later disabled?

Because malidp_crtc_atomic_enable() returns void, the DRM core still
considers the CRTC active even if it returns early on error here. When the
CRTC is later disabled, malidp_crtc_atomic_disable() will be unconditionally
called, which executes its own pm_runtime_put():

drivers/gpu/drm/arm/malidp_crtc.c:malidp_crtc_atomic_disable() {
	...
	clk_disable_unprepare(hwdev->pxlclk);

	pm_runtime_put(crtc->dev->dev);
}

If we drop the PM reference here on the error path, wouldn't the later call
to pm_runtime_put() in malidp_crtc_atomic_disable() result in a double-put
and underflow the PM usage counter?

>  		return;
>  	}
>

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Sashiko AI review · https://sashiko.dev/#/patchset/20260916102112.2018372-1-vulab@iscas.ac.cn?part=1