Re: [PATCH v2] iio: adc: exynos_adc: Replace indio_dev->mlock with own device lock

[Jonathan Cameron <jic23@kernel.org>]

On Wed, 16 Sep 2020 12:31:23 +0300
Alexandru Ardelean <alexandru.ardelean@analog.com> wrote:

> From: Sergiu Cuciurean <sergiu.cuciurean@analog.com>
> 
> As part of the general cleanup of indio_dev->mlock, this change replaces
> it with a local lock, to protect potential concurrent access to the
> completion callback during a conversion.
> 
> This is part of a bigger cleanup.
> Link: https://lore.kernel.org/linux-iio/CA+U=Dsoo6YABe5ODLp+eFNPGFDjk5ZeQEceGkqjxXcVEhLWubw@mail.gmail.com/
> 
> Reviewed-by: Krzysztof Kozlowski <krzk@kernel.org>
> Signed-off-by: Sergiu Cuciurean <sergiu.cuciurean@analog.com>
> Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
Applied to the togreg branch of iio.git and pushed out as testing for the
autobuilders to play with it.

Thanks,

Jonathan

> ---
>  drivers/iio/adc/exynos_adc.c | 20 ++++++++++++++++----
>  1 file changed, 16 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/iio/adc/exynos_adc.c b/drivers/iio/adc/exynos_adc.c
> index 20477b249f2a..99f4404e9fd1 100644
> --- a/drivers/iio/adc/exynos_adc.c
> +++ b/drivers/iio/adc/exynos_adc.c
> @@ -138,6 +138,16 @@ struct exynos_adc {
>  	bool			read_ts;
>  	u32			ts_x;
>  	u32			ts_y;
> +
> +	/*
> +	 * Lock to protect from potential concurrent access to the
> +	 * completion callback during a manual conversion. For this driver
> +	 * a wait-callback is used to wait for the conversion result,
> +	 * so in the meantime no other read request (or conversion start)
> +	 * must be performed, otherwise it would interfere with the
> +	 * current conversion result.
> +	 */
> +	struct mutex		lock;
>  };
>  
>  struct exynos_adc_data {
> @@ -542,7 +552,7 @@ static int exynos_read_raw(struct iio_dev *indio_dev,
>  		return -EINVAL;
>  	}
>  
> -	mutex_lock(&indio_dev->mlock);
> +	mutex_lock(&info->lock);
>  	reinit_completion(&info->completion);
>  
>  	/* Select the channel to be used and Trigger conversion */
> @@ -562,7 +572,7 @@ static int exynos_read_raw(struct iio_dev *indio_dev,
>  		ret = IIO_VAL_INT;
>  	}
>  
> -	mutex_unlock(&indio_dev->mlock);
> +	mutex_unlock(&info->lock);
>  
>  	return ret;
>  }
> @@ -573,7 +583,7 @@ static int exynos_read_s3c64xx_ts(struct iio_dev *indio_dev, int *x, int *y)
>  	unsigned long timeout;
>  	int ret;
>  
> -	mutex_lock(&indio_dev->mlock);
> +	mutex_lock(&info->lock);
>  	info->read_ts = true;
>  
>  	reinit_completion(&info->completion);
> @@ -598,7 +608,7 @@ static int exynos_read_s3c64xx_ts(struct iio_dev *indio_dev, int *x, int *y)
>  	}
>  
>  	info->read_ts = false;
> -	mutex_unlock(&indio_dev->mlock);
> +	mutex_unlock(&info->lock);
>  
>  	return ret;
>  }
> @@ -868,6 +878,8 @@ static int exynos_adc_probe(struct platform_device *pdev)
>  	indio_dev->channels = exynos_adc_iio_channels;
>  	indio_dev->num_channels = info->data->num_channels;
>  
> +	mutex_init(&info->lock);
> +
>  	ret = request_irq(info->irq, exynos_adc_isr,
>  					0, dev_name(&pdev->dev), info);
>  	if (ret < 0) {