RE: [PATCH v8 1/2] iio: frequency: adrf6780: add support for ADRF6780

[Miclaus, Antoniu]

Hello Jonathan,

Would you like me to reintroduce the locked/unlocked version for the "adrf6780_spi_update_bits" function too?
This was present in the first version of the driver but removed afterwards based on the review.

Regards,
--
Antoniu Miclăuş

> -----Original Message-----
> From: Jonathan Cameron <jic23@xxxxxxxxxx>
> Sent: Wednesday, October 20, 2021 11:24 PM
> To: Miclaus, Antoniu <Antoniu.Miclaus@xxxxxxxxxx>
> Cc: linux-kernel@xxxxxxxxxxxxxxx; linux-iio@xxxxxxxxxxxxxxx
> Subject: Re: [PATCH v8 1/2] iio: frequency: adrf6780: add support for
> ADRF6780
> 
> [External]
> 
> On Mon, 18 Oct 2021 14:09:30 +0300
> Antoniu Miclaus <antoniu.miclaus@xxxxxxxxxx> wrote:
> 
> > The ADRF6780 is a silicon germanium (SiGe) design, wideband,
> > microwave upconverter optimized for point to point microwave
> > radio designs operating in the 5.9 GHz to 23.6 GHz frequency
> > range.
> >
> > Datasheet:
> > https://www.analog.com/media/en/technical-documentation/data-
> sheets/ADRF6780.pdf
> >
> > Signed-off-by: Antoniu Miclaus <antoniu.miclaus@xxxxxxxxxx>
> 
> The 'problem' with rereading drivers lots of times is sometimes
> you notice a new issue that you've missed before.  Unfortunately
> the locking in here is inconsistent and there is not protection against
> various functions using the dev->data[] array at the same time.
> Sorry I missed this in earlier reviews!
> 
> It's a little bit too fiddly for me to simply make the changes
> whilst applying, so please add the missing mutex_lock/unlock
> and send out a v9.  I would suggest doing it by renaming the existing
> unlocked versions to
> __XXX_write() /read()
> and then adding functions which take the mutex called after their
> original names.
> 
> I made a small additional comment on naming that would also be good to
> clear up.
> 
> Plus please run scripts/checkpatch.pl over the file and fix the warnings.
> Preferably with --strict
> 
> Thanks,
> 
> Jonathan
> 
> > ---
> > changes in v8:
> > 	- condense lines that are very long
> > 	- set ADC channel as input
> > 	- add `dev_err_probe`
> > 	- handle device powerdown via `devm_add_action_or_reset`
> >  drivers/iio/frequency/Kconfig    |  12 +
> >  drivers/iio/frequency/Makefile   |   1 +
> >  drivers/iio/frequency/adrf6780.c | 496
> +++++++++++++++++++++++++++++++
> >  3 files changed, 509 insertions(+)
> >  create mode 100644 drivers/iio/frequency/adrf6780.c
> >
> > diff --git a/drivers/iio/frequency/Kconfig b/drivers/iio/frequency/Kconfig
> > index 240b81502512..2c9e0559e8a4 100644
> > --- a/drivers/iio/frequency/Kconfig
> > +++ b/drivers/iio/frequency/Kconfig
> > @@ -49,5 +49,17 @@ config ADF4371
> >
> >  	  To compile this driver as a module, choose M here: the
> >  	  module will be called adf4371.
> > +
> > +config ADRF6780
> > +        tristate "Analog Devices ADRF6780 Microwave Upconverter"
> > +        depends on SPI
> > +        depends on COMMON_CLK
> > +        help
> > +          Say yes here to build support for Analog Devices ADRF6780
> > +          5.9 GHz to 23.6 GHz, Wideband, Microwave Upconverter.
> > +
> > +          To compile this driver as a module, choose M here: the
> > +          module will be called adrf6780.
> > +
> >  endmenu
> >  endmenu
> > diff --git a/drivers/iio/frequency/Makefile
> b/drivers/iio/frequency/Makefile
> > index 518b1e50caef..ae3136c79202 100644
> > --- a/drivers/iio/frequency/Makefile
> > +++ b/drivers/iio/frequency/Makefile
> > @@ -7,3 +7,4 @@
> >  obj-$(CONFIG_AD9523) += ad9523.o
> >  obj-$(CONFIG_ADF4350) += adf4350.o
> >  obj-$(CONFIG_ADF4371) += adf4371.o
> > +obj-$(CONFIG_ADRF6780) += adrf6780.o
> > diff --git a/drivers/iio/frequency/adrf6780.c
> b/drivers/iio/frequency/adrf6780.c
> > new file mode 100644
> > index 000000000000..4097b31bdf0b
> > --- /dev/null
> > +++ b/drivers/iio/frequency/adrf6780.c
> 
> > +
> > +static int adrf6780_spi_read(struct adrf6780_dev *dev, unsigned int reg,
> > +			      unsigned int *val)
> 
> I've highlighted a few paths inline where this isn't protected by a
> mutex.  As such we will be racing on the content of dev->data[]
> and results are going to be very unpredicatable.
> 
> > +{
> > +	int ret;
> > +	struct spi_transfer t = {0};
> > +
> > +	dev->data[0] = 0x80 | (reg << 1);
> > +	dev->data[1] = 0x0;
> > +	dev->data[2] = 0x0;
> > +
> > +	t.rx_buf = &dev->data[0];
> > +	t.tx_buf = &dev->data[0];
> > +	t.len = 3;
> > +
> > +	ret = spi_sync_transfer(dev->spi, &t, 1);
> > +	if (ret)
> > +		return ret;
> > +
> > +	*val = (get_unaligned_be24(&dev->data[0]) >> 1) & GENMASK(15,
> 0);
> > +
> > +	return ret;
> > +}
> > +
> > +static int adrf6780_spi_write(struct adrf6780_dev *dev,
> > +				      unsigned int reg,
> > +				      unsigned int val)
> > +{
> > +	put_unaligned_be24((val << 1) | (reg << 17), &dev->data[0]);
> > +
> > +	return spi_write(dev->spi, &dev->data[0], 3);
> > +}
> > +
> ...
> 
> > +static int adrf6780_read_raw(struct iio_dev *indio_dev,
> > +			    struct iio_chan_spec const *chan,
> > +			    int *val, int *val2, long info)
> > +{
> > +	struct adrf6780_dev *dev = iio_priv(indio_dev);
> > +	unsigned int data;
> > +	int ret;
> > +
> > +	switch (info) {
> > +	case IIO_CHAN_INFO_RAW:
> > +		ret = adrf6780_read_adc_raw(dev, &data);
> 
> This takes the mutex inside the call which is good.
> 
> > +		if (ret)
> > +			return ret;
> > +
> > +		*val = data & ADRF6780_ADC_VALUE_MSK;
> > +
> > +		return IIO_VAL_INT;
> > +
> > +	case IIO_CHAN_INFO_SCALE:
> 
> But need locks here as well (see below)
> 
> > +		ret = adrf6780_spi_read(dev, ADRF6780_REG_LINEARIZE,
> &data);
> > +		if (ret)
> > +			return ret;
> > +
> > +		*val = data & ADRF6780_RDAC_LINEARIZE_MSK;
> > +
> > +		return IIO_VAL_INT;
> > +	case IIO_CHAN_INFO_PHASE:
> 
> And here.
> 
> > +		ret = adrf6780_spi_read(dev, ADRF6780_REG_LO_PATH,
> &data);
> > +		if (ret)
> > +			return ret;
> > +
> > +		switch (chan->channel2) {
> > +		case IIO_MOD_I:
> > +			*val = data &
> ADRF6780_I_PATH_PHASE_ACCURACY_MSK;
> > +
> > +			return IIO_VAL_INT;
> > +		case IIO_MOD_Q:
> > +			*val =
> FIELD_GET(ADRF6780_Q_PATH_PHASE_ACCURACY_MSK, data);
> > +
> > +			return IIO_VAL_INT;
> > +		default:
> > +			return -EINVAL;
> > +		}
> > +	default:
> > +		return -EINVAL;
> > +	}
> > +}
> > +
> > +static int adrf6780_write_raw(struct iio_dev *indio_dev,
> > +			     struct iio_chan_spec const *chan,
> > +			     int val, int val2, long info)
> > +{
> > +	struct adrf6780_dev *dev = iio_priv(indio_dev);
> 
> Minor point but there is a fairly strong expectation than anything
> called simply 'dev' is a struct device.  Consider renaming.
> 
> > +	int ret;
> > +
> > +	switch (info) {
> > +	case IIO_CHAN_INFO_SCALE:
> 
> This needs to take the lock or you can have this using dev->data at the
> same time as other calls which have taken the mutex.
> 
> > +		return adrf6780_spi_write(dev, ADRF6780_REG_LINEARIZE,
> val);
> > +	case IIO_CHAN_INFO_PHASE:
> > +		switch (chan->channel2) {
> > +		case IIO_MOD_I:
> > +			mutex_lock(&dev->lock);
> > +			ret = adrf6780_spi_update_bits(dev,
> ADRF6780_REG_LO_PATH,
> > +
> 	ADRF6780_I_PATH_PHASE_ACCURACY_MSK,
> > +
> 	FIELD_PREP(ADRF6780_I_PATH_PHASE_ACCURACY_MSK, val));
> > +			mutex_unlock(&dev->lock);
> > +
> > +			return ret;
> > +		case IIO_MOD_Q:
> > +			mutex_lock(&dev->lock);
> > +			ret = adrf6780_spi_update_bits(dev,
> ADRF6780_REG_LO_PATH,
> > +
> 	ADRF6780_Q_PATH_PHASE_ACCURACY_MSK,
> > +
> 	FIELD_PREP(ADRF6780_Q_PATH_PHASE_ACCURACY_MSK, val));
> > +			mutex_unlock(&dev->lock);
> > +
> > +			return ret;
> > +		default:
> > +			return -EINVAL;
> > +		}
> > +	default:
> > +		return -EINVAL;
> > +	}
> > +}
> > +
> > +static int adrf6780_reg_access(struct iio_dev *indio_dev,
> > +				unsigned int reg,
> > +				unsigned int write_val,
> > +				unsigned int *read_val)
> > +{
> > +	struct adrf6780_dev *dev = iio_priv(indio_dev);
> > +
> > +	if (read_val)
> 
> Nothing prevents these being concurrent with other accesses
> using the st->buf either.
> 
> > +		return adrf6780_spi_read(dev, reg, read_val);
> > +	else
> > +		return adrf6780_spi_write(dev, reg, write_val);
> > +}
> > +
> ...