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

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On Sat, 2018-06-30 at 18:30 +0100, Jonathan Cameron wrote:
> On Mon, 25 Jun 2018 11:01:17 +0300
> Alexandru Ardelean <alexandru.ardelean@xxxxxxxxxx> wrote:
> 
> > From: Lars-Peter Clausen <lars@xxxxxxxxxx>
> > 
> > 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@xxxxxxxxxx>
> > Signed-off-by: Alexandru Ardelean <alexandru.ardelean@xxxxxxxxxx>
> 
> 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.

Ack.
Will come back with a V2.

Thanks
Alex

> 
> Jonathan
> 
> > ---
> > 
> > v1 -> v2:
> > * added Signed-off-by: Alexandru Ardelean <alexandru.ardelean@xxxxxxxxx
> > m>
> > 
> >  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_C
> > LK_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);
> 
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