Re: [PATCH V2] iio: ad9523: replace core mlock with local lock

[Jonathan Cameron <jic23@kernel.org>]

On Mon, 25 Jun 2018 11:01:17 +0300
Alexandru Ardelean <alexandru.ardelean@analog.com> wrote:

> From: Lars-Peter Clausen <lars@metafoo.de>
> 
> This is part of a long term effort to make the use of mlock opaque and
> single purpose.
> 
> Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
> Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>

Patch is fine, but I'd like to see precise documentation for the
scope of the lock.  These things can be awfully 'fuzzy' so good
to define this explicitly.

Jonathan

> ---
> 
> v1 -> v2:
> * added Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
> 
>  drivers/iio/frequency/ad9523.c | 27 +++++++++++++++++----------
>  1 file changed, 17 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/iio/frequency/ad9523.c b/drivers/iio/frequency/ad9523.c
> index ddb6a334ae68..1b70e8a13338 100644
> --- a/drivers/iio/frequency/ad9523.c
> +++ b/drivers/iio/frequency/ad9523.c
> @@ -274,6 +274,8 @@ struct ad9523_state {
>  	unsigned long		vco_out_freq[AD9523_NUM_CLK_SRC];
>  	unsigned char		vco_out_map[AD9523_NUM_CHAN_ALT_CLK_SRC];
>  

I'd like to see a precise definition of what this lock is intended
to protect.  Not to mention checkpatch will moan about it I think
if there is nothing here ;)

> +	struct mutex		lock;
> +
>  	/*
>  	 * DMA (thus cache coherency maintenance) requires the
>  	 * transfer buffers to live in their own cache lines.
> @@ -500,6 +502,7 @@ static ssize_t ad9523_store(struct device *dev,
>  {
>  	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
>  	struct iio_dev_attr *this_attr = to_iio_dev_attr(attr);
> +	struct ad9523_state *st = iio_priv(indio_dev);
>  	bool state;
>  	int ret;
>  
> @@ -510,7 +513,7 @@ static ssize_t ad9523_store(struct device *dev,
>  	if (!state)
>  		return 0;
>  
> -	mutex_lock(&indio_dev->mlock);
> +	mutex_lock(&st->lock);
>  	switch ((u32)this_attr->address) {
>  	case AD9523_SYNC:
>  		ret = ad9523_sync(indio_dev);
> @@ -521,7 +524,7 @@ static ssize_t ad9523_store(struct device *dev,
>  	default:
>  		ret = -ENODEV;
>  	}
> -	mutex_unlock(&indio_dev->mlock);
> +	mutex_unlock(&st->lock);
>  
>  	return ret ? ret : len;
>  }
> @@ -532,15 +535,16 @@ static ssize_t ad9523_show(struct device *dev,
>  {
>  	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
>  	struct iio_dev_attr *this_attr = to_iio_dev_attr(attr);
> +	struct ad9523_state *st = iio_priv(indio_dev);
>  	int ret;
>  
> -	mutex_lock(&indio_dev->mlock);
> +	mutex_lock(&st->lock);
>  	ret = ad9523_read(indio_dev, AD9523_READBACK_0);
>  	if (ret >= 0) {
>  		ret = sprintf(buf, "%d\n", !!(ret & (1 <<
>  			(u32)this_attr->address)));
>  	}
> -	mutex_unlock(&indio_dev->mlock);
> +	mutex_unlock(&st->lock);
>  
>  	return ret;
>  }
> @@ -623,9 +627,9 @@ static int ad9523_read_raw(struct iio_dev *indio_dev,
>  	unsigned int code;
>  	int ret;
>  
> -	mutex_lock(&indio_dev->mlock);
> +	mutex_lock(&st->lock);
>  	ret = ad9523_read(indio_dev, AD9523_CHANNEL_CLOCK_DIST(chan->channel));
> -	mutex_unlock(&indio_dev->mlock);
> +	mutex_unlock(&st->lock);
>  
>  	if (ret < 0)
>  		return ret;
> @@ -659,7 +663,7 @@ static int ad9523_write_raw(struct iio_dev *indio_dev,
>  	unsigned int reg;
>  	int ret, tmp, code;
>  
> -	mutex_lock(&indio_dev->mlock);
> +	mutex_lock(&st->lock);
>  	ret = ad9523_read(indio_dev, AD9523_CHANNEL_CLOCK_DIST(chan->channel));
>  	if (ret < 0)
>  		goto out;
> @@ -705,7 +709,7 @@ static int ad9523_write_raw(struct iio_dev *indio_dev,
>  
>  	ad9523_io_update(indio_dev);
>  out:
> -	mutex_unlock(&indio_dev->mlock);
> +	mutex_unlock(&st->lock);
>  	return ret;
>  }
>  
> @@ -713,9 +717,10 @@ static int ad9523_reg_access(struct iio_dev *indio_dev,
>  			      unsigned int reg, unsigned int writeval,
>  			      unsigned int *readval)
>  {
> +	struct ad9523_state *st = iio_priv(indio_dev);
>  	int ret;
>  
> -	mutex_lock(&indio_dev->mlock);
> +	mutex_lock(&st->lock);
>  	if (readval == NULL) {
>  		ret = ad9523_write(indio_dev, reg | AD9523_R1B, writeval);
>  		ad9523_io_update(indio_dev);
> @@ -728,7 +733,7 @@ static int ad9523_reg_access(struct iio_dev *indio_dev,
>  	}
>  
>  out_unlock:
> -	mutex_unlock(&indio_dev->mlock);
> +	mutex_unlock(&st->lock);
>  
>  	return ret;
>  }
> @@ -967,6 +972,8 @@ static int ad9523_probe(struct spi_device *spi)
>  
>  	st = iio_priv(indio_dev);
>  
> +	mutex_init(&st->lock);
> +
>  	st->reg = devm_regulator_get(&spi->dev, "vcc");
>  	if (!IS_ERR(st->reg)) {
>  		ret = regulator_enable(st->reg);