linux-kernel - Re: [PATCH v3] Fix IRQ issue by setting IRQ_DISABLE

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Message-ID: <20230423121528.259d3cd4@jic23-huawei>
Date:   Sun, 23 Apr 2023 12:15:28 +0100
From:   Jonathan Cameron <jic23@...nel.org>
To:     Masahiro Honda <honda@...hatrax.com>
Cc:     Lars-Peter Clausen <lars@...afoo.de>,
        Michael Hennerich <Michael.Hennerich@...log.com>,
        linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] Fix IRQ issue by setting IRQ_DISABLE_UNLAZY flag

On Thu, 20 Apr 2023 19:23:16 +0900
Masahiro Honda <honda@...hatrax.com> wrote:

> The Sigma-Delta ADCs supported by this driver can use SDO as an interrupt
> line to indicate the completion of a conversion. However, some devices
> cannot properly detect the completion of a conversion by an interrupt.
> This is for the reason mentioned in the following commit.
> 
> commit e9849777d0e2 ("genirq: Add flag to force mask in
>                       disable_irq[_nosync]()")
> 
> A read operation is performed by an extra interrupt before the completion
> of a conversion. This patch fixes the issue by setting IRQ_DISABLE_UNLAZY
> flag.
> 
> Signed-off-by: Masahiro Honda <honda@...hatrax.com>
> ---
> v3:
>  - Remove the Kconfig option.
> v2: https://lore.kernel.org/linux-iio/20230414102744.150-1-honda@mechatrax.com/
>  - Rework commit message.
>  - Add a new entry in the Kconfig.
>  - Call irq_clear_status_flags(irq, IRQ_DISABLE_UNLAZY) when freeing the IRQ.
> v1: https://lore.kernel.org/linux-iio/20230306044737.862-1-honda@mechatrax.com/
> 
>  drivers/iio/adc/ad_sigma_delta.c | 25 ++++++++++++++++++++-----
>  1 file changed, 20 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/iio/adc/ad_sigma_delta.c b/drivers/iio/adc/ad_sigma_delta.c
> index d8570f620..215ecbedb 100644
> --- a/drivers/iio/adc/ad_sigma_delta.c
> +++ b/drivers/iio/adc/ad_sigma_delta.c
> @@ -565,6 +565,14 @@ int ad_sd_validate_trigger(struct iio_dev *indio_dev, struct iio_trigger *trig)
>  }
>  EXPORT_SYMBOL_NS_GPL(ad_sd_validate_trigger, IIO_AD_SIGMA_DELTA);
>  
> +static void ad_sd_free_irq(void *sd)
> +{
> +	struct ad_sigma_delta *sigma_delta = sd;
> +
> +	irq_clear_status_flags(sigma_delta->spi->irq, IRQ_DISABLE_UNLAZY);
> +	free_irq(sigma_delta->spi->irq, sigma_delta);
> +}

Don't fuse the two operations unwinding like this.  Just register a callback that only
does the irq_clear_status_flags immediately after setting them.  Then leave
the orginally devm_request_irq call alone.  If it fails, the devm cleanup will
deal with the irq_clear_status_flag for you.

It almost never makes sense for a single devm call to unwind more than one function call in
a driver.

Otherwise this looks fine to me,

Thanks,

Jonathan



> +
>  static int devm_ad_sd_probe_trigger(struct device *dev, struct iio_dev *indio_dev)
>  {
>  	struct ad_sigma_delta *sigma_delta = iio_device_get_drvdata(indio_dev);
> @@ -584,11 +592,18 @@ static int devm_ad_sd_probe_trigger(struct device *dev, struct iio_dev *indio_de
>  	init_completion(&sigma_delta->completion);
>  
>  	sigma_delta->irq_dis = true;
> -	ret = devm_request_irq(dev, sigma_delta->spi->irq,
> -			       ad_sd_data_rdy_trig_poll,
> -			       sigma_delta->info->irq_flags | IRQF_NO_AUTOEN,
> -			       indio_dev->name,
> -			       sigma_delta);
> +	irq_set_status_flags(sigma_delta->spi->irq, IRQ_DISABLE_UNLAZY);
> +	ret = request_irq(sigma_delta->spi->irq,
> +			  ad_sd_data_rdy_trig_poll,
> +			  sigma_delta->info->irq_flags | IRQF_NO_AUTOEN,
> +			  indio_dev->name,
> +			  sigma_delta);
> +	if (ret) {
> +		irq_clear_status_flags(sigma_delta->spi->irq, IRQ_DISABLE_UNLAZY);
> +		return ret;
> +	}
> +
> +	ret = devm_add_action_or_reset(dev, ad_sd_free_irq, sigma_delta);
>  	if (ret)
>  		return ret;
>