RE: [PATCH v2 10/16] iio: adc: vf610_adc: vf610_adc: do not use internal iio_dev lock

[Bough Chen <haibo.chen@nxp.com>]

> -----Original Message-----
> From: Nuno Sá <nuno.sa@analog.com>
> Sent: 2022年10月4日 21:49
> To: linux-amlogic@lists.infradead.org; dl-linux-imx <linux-imx@nxp.com>;
> linux-iio@vger.kernel.org; linux-arm-kernel@lists.infradead.org;
> linux-rockchip@lists.infradead.org
> Cc: Heiko Stuebner <heiko@sntech.de>; Martin Blumenstingl
> <martin.blumenstingl@googlemail.com>; Neil Armstrong
> <narmstrong@baylibre.com>; Shawn Guo <shawnguo@kernel.org>; Lars-Peter
> Clausen <lars@metafoo.de>; Jyoti Bhayana <jbhayana@google.com>; Hans de
> Goede <hdegoede@redhat.com>; Andriy Tryshnivskyy
> <andriy.tryshnivskyy@opensynergy.com>; Pengutronix Kernel Team
> <kernel@pengutronix.de>; Miquel Raynal <miquel.raynal@bootlin.com>; Cixi
> Geng <cixi.geng1@unisoc.com>; Baolin Wang
> <baolin.wang@linux.alibaba.com>; Ciprian Regus <ciprian.regus@analog.com>;
> Fabio Estevam <festevam@gmail.com>; Nuno Sá <nuno.sa@analog.com>;
> Sascha Hauer <s.hauer@pengutronix.de>; Alexandru Ardelean
> <aardelean@deviqon.com>; Florian Boor <florian.boor@kernelconcepts.de>;
> Michael Hennerich <Michael.Hennerich@analog.com>; Orson Zhai
> <orsonzhai@gmail.com>; Chen-Yu Tsai <wens@csie.org>; Chunyan Zhang
> <zhang.lyra@gmail.com>; Vladimir Zapolskiy <vz@mleia.com>; Andy
> Shevchenko <andy.shevchenko@gmail.com>; Jerome Brunet
> <jbrunet@baylibre.com>; Bough Chen <haibo.chen@nxp.com>; Kevin Hilman
> <khilman@baylibre.com>; Jonathan Cameron <jic23@kernel.org>
> Subject: [PATCH v2 10/16] iio: adc: vf610_adc: vf610_adc: do not use internal
> iio_dev lock
> 
> In order to drop the internal lock usage we needed two different things:
> 
> 1) The first place where 'mlock' was being used was a typical case where
> iio_device_claim_direct_mode() fits perfectly.
> 2) In the second case, it was being used to prevent concurrent accesses to the
> device and shared data but nothing was being enforced with regards to
> buffering (i.e, there was nothing preventing from changing the conversion mode
> while buffering). Hence, in this case, a new lock was introduced in the state
> structure.
> 
> Note that the goal is not to introduce any functional change and that is the
> reason why a new lock was introduced to guarantee 2).
> 
> While at it, properly include "mutex.h" for mutex related APIs.
> 
> Signed-off-by: Nuno Sá <nuno.sa@analog.com>

Reviewed-by: Haibo Chen <haibo.chen@nxp.com>

Thanks!

> ---
>  drivers/iio/adc/vf610_adc.c | 22 ++++++++++++++--------
>  1 file changed, 14 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/iio/adc/vf610_adc.c b/drivers/iio/adc/vf610_adc.c index
> a6f9182d7766..ae31aafd2653 100644
> --- a/drivers/iio/adc/vf610_adc.c
> +++ b/drivers/iio/adc/vf610_adc.c
> @@ -7,6 +7,7 @@
> 
>  #include <linux/mod_devicetable.h>
>  #include <linux/module.h>
> +#include <linux/mutex.h>
>  #include <linux/property.h>
>  #include <linux/platform_device.h>
>  #include <linux/interrupt.h>
> @@ -156,6 +157,9 @@ struct vf610_adc {
>  	void __iomem *regs;
>  	struct clk *clk;
> 
> +	/* lock to protect against multiple access to the device */
> +	struct mutex lock;
> +
>  	u32 vref_uv;
>  	u32 value;
>  	struct regulator *vref;
> @@ -467,11 +471,11 @@ static int vf610_set_conversion_mode(struct iio_dev
> *indio_dev,  {
>  	struct vf610_adc *info = iio_priv(indio_dev);
> 
> -	mutex_lock(&indio_dev->mlock);
> +	mutex_lock(&info->lock);
>  	info->adc_feature.conv_mode = mode;
>  	vf610_adc_calculate_rates(info);
>  	vf610_adc_hw_init(info);
> -	mutex_unlock(&indio_dev->mlock);
> +	mutex_unlock(&info->lock);
> 
>  	return 0;
>  }
> @@ -629,12 +633,11 @@ static int vf610_read_sample(struct iio_dev
> *indio_dev,
>  	unsigned int hc_cfg;
>  	int ret;
> 
> -	mutex_lock(&indio_dev->mlock);
> -	if (iio_buffer_enabled(indio_dev)) {
> -		ret = -EBUSY;
> -		goto out_unlock;
> -	}
> +	ret = iio_device_claim_direct_mode(indio_dev);
> +	if (ret)
> +		return ret;
> 
> +	mutex_lock(&info->lock);
>  	reinit_completion(&info->completion);
>  	hc_cfg = VF610_ADC_ADCHC(chan->channel);
>  	hc_cfg |= VF610_ADC_AIEN;
> @@ -669,7 +672,8 @@ static int vf610_read_sample(struct iio_dev *indio_dev,
>  	}
> 
>  out_unlock:
> -	mutex_unlock(&indio_dev->mlock);
> +	mutex_unlock(&info->lock);
> +	iio_device_release_direct_mode(indio_dev);
> 
>  	return ret;
>  }
> @@ -892,6 +896,8 @@ static int vf610_adc_probe(struct platform_device
> *pdev)
>  		goto error_iio_device_register;
>  	}
> 
> +	mutex_init(&info->lock);
> +
>  	ret = iio_device_register(indio_dev);
>  	if (ret) {
>  		dev_err(&pdev->dev, "Couldn't register the device.\n");
> --
> 2.37.3

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