Re: [PATCH 1/2] iio: adc: rzg2l_adc: Drop devm_pm_runtime_enable()

[Ulf Hansson]

On Fri, 3 Jan 2025 at 15:00, Claudiu <claudiu.beznea@xxxxxxxxx> wrote:
>
> From: Claudiu Beznea <claudiu.beznea.uj@xxxxxxxxxxxxxx>
>
> On all systems where the rzg2l_adc driver is used, the ADC clocks are part
> of a PM domain. The code that implements the PM domains support is in
> drivers/clk/renesas/rzg2l-cpg.c, the functions of interest for this commit
> being rzg2l_cpg_attach_dev() and rzg2l_cpg_deattach_dev(). The PM
> domains support is registered with GENPD_FLAG_PM_CLK which, according to
> the documentation, instructs genpd to use the PM clk framework while
> powering on/off attached devices.
>
> During probe, the ADC device is attached to the PM domain
> controlling the ADC clocks. Similarly, during removal, the ADC device is
> detached from the PM domain.
>
> The detachment call stack is as follows:
>
> device_driver_detach() ->
>   device_release_driver_internal() ->
>     __device_release_driver() ->
>       device_remove() ->
>         platform_remove() ->
>           dev_pm_domain_detach()
>
> During driver unbind, after the ADC device is detached from its PM domain,
> the device_unbind_cleanup() function is called, which subsequently invokes
> devres_release_all(). This function handles devres resource cleanup.
>
> If runtime PM is enabled via devm_pm_runtime_enable(), the cleanup process
> triggers the action or reset function for disabling runtime PM. This
> function is pm_runtime_disable_action(), which leads to the following call
> stack of interest when called:
>
> pm_runtime_disable_action() ->
>   pm_runtime_dont_use_autosuspend() ->
>     __pm_runtime_use_autosuspend() ->
>       update_autosuspend() ->
>         rpm_idle()
>
> The rpm_idle() function attempts to runtime resume the ADC device. However,
> at the point it is called, the ADC device is no longer part of the PM
> domain (which manages the ADC clocks). Since the rzg2l_adc runtime PM
> APIs directly modifies hardware registers, the
> rzg2l_adc_pm_runtime_resume() function is invoked without the ADC clocks
> being enabled. This is because the PM domain no longer resumes along with
> the ADC device. As a result, this leads to system aborts.
>
> Drop the devres API for runtime PM enable.
>
> Fixes: 89ee8174e8c8 ("iio: adc: rzg2l_adc: Simplify the runtime PM code")
> Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@xxxxxxxxxxxxxx>

Reviewed-by: Ulf Hansson <ulf.hansson@xxxxxxxxxx>

Kind regards
Uffe

> ---
>  drivers/iio/adc/rzg2l_adc.c | 33 ++++++++++++++++++++++++---------
>  1 file changed, 24 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/iio/adc/rzg2l_adc.c b/drivers/iio/adc/rzg2l_adc.c
> index 883c167c0670..f12f3daf08cc 100644
> --- a/drivers/iio/adc/rzg2l_adc.c
> +++ b/drivers/iio/adc/rzg2l_adc.c
> @@ -464,25 +464,26 @@ static int rzg2l_adc_probe(struct platform_device *pdev)
>
>         pm_runtime_set_autosuspend_delay(dev, 300);
>         pm_runtime_use_autosuspend(dev);
> -       ret = devm_pm_runtime_enable(dev);
> -       if (ret)
> -               return ret;
> +       pm_runtime_enable(dev);
>
>         platform_set_drvdata(pdev, indio_dev);
>
>         ret = rzg2l_adc_hw_init(dev, adc);
> -       if (ret)
> -               return dev_err_probe(&pdev->dev, ret,
> -                                    "failed to initialize ADC HW\n");
> +       if (ret) {
> +               dev_err_probe(&pdev->dev, ret, "failed to initialize ADC HW\n");
> +               goto rpm_disable;
> +       }
>
>         irq = platform_get_irq(pdev, 0);
> -       if (irq < 0)
> -               return irq;
> +       if (irq < 0) {
> +               ret = irq;
> +               goto rpm_disable;
> +       }
>
>         ret = devm_request_irq(dev, irq, rzg2l_adc_isr,
>                                0, dev_name(dev), adc);
>         if (ret < 0)
> -               return ret;
> +               goto rpm_disable;
>
>         init_completion(&adc->completion);
>
> @@ -493,6 +494,19 @@ static int rzg2l_adc_probe(struct platform_device *pdev)
>         indio_dev->num_channels = adc->data->num_channels;
>
>         return devm_iio_device_register(dev, indio_dev);
> +
> +rpm_disable:
> +       pm_runtime_disable(dev);
> +       pm_runtime_dont_use_autosuspend(dev);
> +       return ret;
> +}
> +
> +static void rzg2l_adc_remove(struct platform_device *pdev)
> +{
> +       struct device *dev = &pdev->dev;
> +
> +       pm_runtime_disable(dev);
> +       pm_runtime_dont_use_autosuspend(dev);
>  }
>
>  static const struct rzg2l_adc_hw_params rzg2l_hw_params = {
> @@ -614,6 +628,7 @@ static const struct dev_pm_ops rzg2l_adc_pm_ops = {
>
>  static struct platform_driver rzg2l_adc_driver = {
>         .probe          = rzg2l_adc_probe,
> +       .remove         = rzg2l_adc_remove,
>         .driver         = {
>                 .name           = DRIVER_NAME,
>                 .of_match_table = rzg2l_adc_match,
> --
> 2.43.0
>