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Message-ID: <CA+V-a8s+-ZS-Y7D1FmdKfVoH5i3Ee86KgYQC6QyfdE0ygDMt+A@mail.gmail.com>
Date: Tue, 25 Feb 2025 20:35:14 +0000
From: "Lad, Prabhakar" <prabhakar.csengg@...il.com>
To: Claudiu <claudiu.beznea@...on.dev>
Cc: prabhakar.mahadev-lad.rj@...renesas.com, jic23@...nel.org, lars@...afoo.de,
linux-iio@...r.kernel.org, linux-renesas-soc@...r.kernel.org,
linux-kernel@...r.kernel.org,
Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
Subject: Re: [PATCH v3 1/2] iio: adc: rzg2l_adc: Open a devres group
On Mon, Feb 24, 2025 at 12:13 PM Claudiu <claudiu.beznea@...on.dev> wrote:
>
> From: Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
>
> 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.
>
> Open a devres group in the driver probe and release it in the driver
> remove. This ensures the runtime PM is disabled (though the devres group)
> after the rzg2l_adc_remove() finishes its execution avoiding the described
> scenario.
>
> Fixes: 89ee8174e8c8 ("iio: adc: rzg2l_adc: Simplify the runtime PM code")
> Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
> ---
>
> Changes in v3:
> - open a devres group in probe and release it in remove; the failure
> path of probe() was also updated to close the devres group
> - dropped Ulf's Rb tag as the patch is different now
> - updated the patch description to match the new approach
>
> Note: a generic approach was proposed in [1] to have this in the platform
> bus itself but wasn't seen acceptable.
>
> [1] https://lore.kernel.org/all/20250215130849.227812-1-claudiu.beznea.uj@bp.renesas.com/
>
> Changes in v2:
> - collected Ulf's tag
> - add a comment above pm_runtime_enable() explaining the reason
> it shouldn't be converted to devres
> - drop devres calls that request IRQ and register IIO device
> as proposed in the review process: Ulf, I still kept you Rb
> tag; please let me know otherwise
>
> drivers/iio/adc/rzg2l_adc.c | 88 ++++++++++++++++++++++++++++---------
> 1 file changed, 67 insertions(+), 21 deletions(-)
>
Reviewed-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
Cheers,
Prabhakar
> diff --git a/drivers/iio/adc/rzg2l_adc.c b/drivers/iio/adc/rzg2l_adc.c
> index 883c167c0670..7db04416e1cf 100644
> --- a/drivers/iio/adc/rzg2l_adc.c
> +++ b/drivers/iio/adc/rzg2l_adc.c
> @@ -85,6 +85,7 @@ struct rzg2l_adc {
> struct reset_control *adrstn;
> const struct rzg2l_adc_data *data;
> const struct rzg2l_adc_hw_params *hw_params;
> + void *devres_group_id;
> struct completion completion;
> struct mutex lock;
> u16 last_val[RZG2L_ADC_MAX_CHANNELS];
> @@ -429,60 +430,88 @@ static int rzg2l_adc_probe(struct platform_device *pdev)
> struct device *dev = &pdev->dev;
> struct iio_dev *indio_dev;
> struct rzg2l_adc *adc;
> + void *devres_group_id;
> int ret;
> int irq;
>
> - indio_dev = devm_iio_device_alloc(dev, sizeof(*adc));
> - if (!indio_dev)
> + /*
> + * Open a devres group to allow using devm_pm_runtime_enable()
> + * w/o interfeering with dev_pm_genpd_detach() in the platform bus
> + * remove. Otherwise, durring repeated unbind/bind operations,
> + * the ADC may be runtime resumed when it is not part of its power
> + * domain, leading to accessing ADC registers without its clocks
> + * being enabled and its PM domain being turned on.
> + */
> + devres_group_id = devres_open_group(dev, NULL, GFP_KERNEL);
> + if (!devres_group_id)
> return -ENOMEM;
>
> + indio_dev = devm_iio_device_alloc(dev, sizeof(*adc));
> + if (!indio_dev) {
> + ret = -ENOMEM;
> + goto release_group;
> + }
> +
> adc = iio_priv(indio_dev);
>
> + adc->devres_group_id = devres_group_id;
> adc->hw_params = device_get_match_data(dev);
> - if (!adc->hw_params || adc->hw_params->num_channels > RZG2L_ADC_MAX_CHANNELS)
> - return -EINVAL;
> + if (!adc->hw_params || adc->hw_params->num_channels > RZG2L_ADC_MAX_CHANNELS) {
> + ret = -EINVAL;
> + goto release_group;
> + }
>
> ret = rzg2l_adc_parse_properties(pdev, adc);
> if (ret)
> - return ret;
> + goto release_group;
>
> mutex_init(&adc->lock);
>
> adc->base = devm_platform_ioremap_resource(pdev, 0);
> - if (IS_ERR(adc->base))
> - return PTR_ERR(adc->base);
> + if (IS_ERR(adc->base)) {
> + ret = PTR_ERR(adc->base);
> + goto release_group;
> + }
>
> adc->adrstn = devm_reset_control_get_exclusive_deasserted(dev, "adrst-n");
> - if (IS_ERR(adc->adrstn))
> - return dev_err_probe(dev, PTR_ERR(adc->adrstn),
> - "failed to get/deassert adrst-n\n");
> + if (IS_ERR(adc->adrstn)) {
> + ret = dev_err_probe(dev, PTR_ERR(adc->adrstn),
> + "failed to get/deassert adrst-n\n");
> + goto release_group;
> + }
>
> adc->presetn = devm_reset_control_get_exclusive_deasserted(dev, "presetn");
> - if (IS_ERR(adc->presetn))
> - return dev_err_probe(dev, PTR_ERR(adc->presetn),
> - "failed to get/deassert presetn\n");
> + if (IS_ERR(adc->presetn)) {
> + ret = dev_err_probe(dev, PTR_ERR(adc->presetn),
> + "failed to get/deassert presetn\n");
> + goto release_group;
> + }
>
> pm_runtime_set_autosuspend_delay(dev, 300);
> pm_runtime_use_autosuspend(dev);
> ret = devm_pm_runtime_enable(dev);
> if (ret)
> - return ret;
> + goto release_group;
>
> 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) {
> + ret = dev_err_probe(&pdev->dev, ret,
> + "failed to initialize ADC HW\n");
> + goto release_group;
> + }
>
> irq = platform_get_irq(pdev, 0);
> - if (irq < 0)
> - return irq;
> + if (irq < 0) {
> + ret = irq;
> + goto release_group;
> + }
>
> ret = devm_request_irq(dev, irq, rzg2l_adc_isr,
> 0, dev_name(dev), adc);
> if (ret < 0)
> - return ret;
> + goto release_group;
>
> init_completion(&adc->completion);
>
> @@ -492,7 +521,23 @@ static int rzg2l_adc_probe(struct platform_device *pdev)
> indio_dev->channels = adc->data->channels;
> indio_dev->num_channels = adc->data->num_channels;
>
> - return devm_iio_device_register(dev, indio_dev);
> + ret = devm_iio_device_register(dev, indio_dev);
> + if (ret)
> + goto release_group;
> +
> + return 0;
> +
> +release_group:
> + devres_release_group(dev, devres_group_id);
> + return ret;
> +}
> +
> +static void rzg2l_adc_remove(struct platform_device *pdev)
> +{
> + struct iio_dev *indio_dev = platform_get_drvdata(pdev);
> + struct rzg2l_adc *adc = iio_priv(indio_dev);
> +
> + devres_release_group(&pdev->dev, adc->devres_group_id);
> }
>
> static const struct rzg2l_adc_hw_params rzg2l_hw_params = {
> @@ -614,6 +659,7 @@ 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
>
>
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