Re: [PATCH] coresight: Fix clock refcount imbalance on platform probe failure

[Leo Yan <leo.yan@arm.com>]

Hi Jie,

Thanks for fixing! It is shame that my single patch caused issues both
in driver's probe and remove - I have to admit that I don't understand
runtime PM's state machine.

TBC, this patch only fixes probe. The driver's remove is fixed in:
https://lore.kernel.org/linux-arm-kernel/20260710-fix-clock-refcount-unbalance-v3-0-a37a1fb17981@oss.qualcomm.com/

The series above and this patch should be picked up together so can
have complete fix.

> The probe wrapper then unconditionally calls pm_runtime_put()
> regardless of whether the inner probe succeeded, so on failure this
> also fires runtime_suspend() and disables the same clocks a first
> time.

pm_runtime_put() can be used for success case, but for the failure
case, we should disable the runtime PM but not release reference:
https://docs.kernel.org/power/runtime_pm.html#runtime-pm-initialization-device-probing-and-removal

> @@ -632,11 +632,14 @@ static int catu_platform_probe(struct platform_device *pdev)
>  	pm_runtime_enable(&pdev->dev);
>  
>  	ret = __catu_probe(&pdev->dev, res);
> -	pm_runtime_put(&pdev->dev);
> -	if (ret)
> +	if (ret) {
> +		pm_runtime_put_noidle(&pdev->dev);
>  		pm_runtime_disable(&pdev->dev);

Nitpick: please reverse the sequence between pm_runtime_put_noidle()
and pm_runtime_disable(). As we need to first disable runtime PM for
the device, then release usage reference.

Since the driver core will reset device's active state, AI told me that
calling pm_runtime_set_suspended() is redundant. It is still good to
explicitly call it for bookkeeping. This can be aligned with the change
in driver remove.

Thus, please update the flow:

        pm_runtime_disable(&pdev->dev);
        pm_runtime_set_suspended(dev);
        pm_runtime_put_noidle(&pdev->dev);

With the update:

Reviewed-by: Leo Yan <leo.yan@arm.com>