Re: [PATCH 1/2] coresight: Fix clock refcount imbalance on platform remove

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

On Wed, Jul 01, 2026 at 02:05:02PM +0800, Jie Gan wrote:

> After probe, pm_runtime_put() allows the device to suspend and the
> runtime suspend callback disables the same clocks. During remove the
> device is left runtime suspended, so pm_runtime_disable() freezes it
> with the clocks already disabled. The devm cleanup that runs afterwards
> calls clk_disable_unprepare() a second time, underflowing the clock
> enable refcount.

Thanks for fixing the issue.

The problem is that if the device has already been runtime suspended and
its clock has been disabled, afterwards when remove the device, the devm
cleanup disables the clock again, resulting in clock count underflow.

> diff --git a/drivers/hwtracing/coresight/coresight-funnel.c b/drivers/hwtracing/coresight/coresight-funnel.c
> index 0abc11f0690c..4c5b94640e6a 100644
> --- a/drivers/hwtracing/coresight/coresight-funnel.c
> +++ b/drivers/hwtracing/coresight/coresight-funnel.c
> @@ -334,6 +334,7 @@ static void funnel_platform_remove(struct platform_device *pdev)
>  		return;
>  
>  	funnel_remove(&pdev->dev);
> +	pm_runtime_get_sync(&pdev->dev);
>  	pm_runtime_disable(&pdev->dev);

Let's use the funnel driver for the discussion. Once we agree on the
approach, we can apply the same change to the other CoreSight platform
drivers.

How about the following teardown?

 static void funnel_platform_remove(struct platform_device *pdev)
 {
        struct funnel_drvdata *drvdata = dev_get_drvdata(&pdev->dev);
+       int ret;

        if (WARN_ON(!drvdata))
                return;

+       ret = pm_runtime_get_sync(&pdev->dev);
+       if (ret < 0)
+               dev_warn(&pdev->dev, "failed to resume before remove: %d\n", ret);
+
        funnel_remove(&pdev->dev);
+
        pm_runtime_disable(&pdev->dev);
+       pm_runtime_set_suspended(&pdev->dev);
+       pm_runtime_put_noidle(&pdev->dev);
 }

The idea is to first resume the device with pm_runtime_get_sync(), then
perform the remove (which is safe if they need to access or clean up
hardware state), and finally clean up the runtime PM states. I mainly
referred to drivers/iio/adc/stm32-adc.c.

Thanks,
Leo