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Date:   Sat, 3 Jul 2021 17:57:16 +0100
From:   Jonathan Cameron <jic23@kernel.org>
To:     Antoniu Miclaus <antoniu.miclaus@analog.com>
Cc:     <linux-iio@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
        <devicetree@vger.kernel.org>, <robh+dt@kernel.org>
Subject: Re: [PATCH v4 1/2] iio: frequency: adrf6780: add support for
 ADRF6780
Message-ID: <20210703175716.7864358a@jic23-huawei>
In-Reply-To: <20210702111239.174189-1-antoniu.miclaus@analog.com>
References: <20210702111239.174189-1-antoniu.miclaus@analog.com>
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On Fri, 2 Jul 2021 14:12:38 +0300
Antoniu Miclaus <antoniu.miclaus@analog.com> 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@analog.com>

Hi Antoniu,

Frequency drivers are fairly unusual so if you could add a listing of
the attributes in sysfs that would be great (it's nice practice anyway but
I don't insist on it!)

Various fairly minor comments inline.

Thanks,

Jonathan


> ---
>  changes in v4:
>   - change license to: GPL-2.0-only
>  drivers/iio/frequency/Kconfig    |  13 +
>  drivers/iio/frequency/Makefile   |   1 +
>  drivers/iio/frequency/adrf6780.c | 498 +++++++++++++++++++++++++++++++
>  3 files changed, 512 insertions(+)
>  create mode 100644 drivers/iio/frequency/adrf6780.c
> 
> diff --git a/drivers/iio/frequency/Kconfig b/drivers/iio/frequency/Kconfig
> index 240b81502512..fc9751c48f59 100644
> --- a/drivers/iio/frequency/Kconfig
> +++ b/drivers/iio/frequency/Kconfig
> @@ -49,5 +49,18 @@ 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
> +        depends on OF

Why?  Pretty much everything seems to have defaults if not provided via OF.
I've asked for the generic firmware functions anyway, so you can drop this
for that reason if nothing else!

> +        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..472a66f90c7f
> --- /dev/null
> +++ b/drivers/iio/frequency/adrf6780.c
> @@ -0,0 +1,498 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * ADRF6780 driver
> + *
> + * Copyright 2021 Analog Devices Inc.
> + */
> +
> +#include <linux/bitfield.h>
> +#include <linux/bits.h>
> +#include <linux/clk.h>
> +#include <linux/clkdev.h>
> +#include <linux/clk-provider.h>
> +#include <linux/delay.h>
> +#include <linux/device.h>
> +#include <linux/iio/iio.h>
> +#include <linux/module.h>

#include <linux/mod_devicetable.h>

> +#include <linux/spi/spi.h>
> +
> +/* ADRF6780 Register Map */
> +#define ADRF6780_REG_CONTROL			0x00
> +#define ADRF6780_REG_ALARM_READBACK		0x01
> +#define ADRF6780_REG_ALARM_MASKS		0x02
> +#define ADRF6780_REG_ENABLE			0x03
> +#define ADRF6780_REG_LINEARIZE			0x04
> +#define ADRF6780_REG_LO_PATH			0x05
> +#define ADRF6780_REG_ADC_CONTROL		0x06
> +#define ADRF6780_REG_ADC_OUTPUT			0x0C
> +
> +/* ADRF6780_REG_CONTROL Map */
> +#define ADRF6780_PARITY_EN_MSK			BIT(15)
> +#define ADRF6780_PARITY_EN(x)			FIELD_PREP(ADRF6780_PARITY_EN_MSK, x)
> +#define ADRF6780_SOFT_RESET_MSK			BIT(14)
> +#define ADRF6780_SOFT_RESET(x)			FIELD_PREP(ADRF6780_SOFT_RESET_MSK, x)
> +#define ADRF6780_CHIP_ID_MSK			GENMASK(11, 4)
> +#define ADRF6780_CHIP_ID			0xA
> +#define ADRF6780_CHIP_REVISION_MSK		GENMASK(3, 0)
> +#define ADRF6780_CHIP_REVISION(x)		FIELD_PREP(ADRF6780_CHIP_REVISION_MSK, x)
> +
> +/* ADRF6780_REG_ALARM_READBACK Map */
> +#define ADRF6780_PARITY_ERROR_MSK		BIT(15)
> +#define ADRF6780_PARITY_ERROR(x)		FIELD_PREP(ADRF6780_PARITY_ERROR_MSK, x)
> +#define ADRF6780_TOO_FEW_ERRORS_MSK		BIT(14)
> +#define ADRF6780_TOO_FEW_ERRORS(x)		FIELD_PREP(ADRF6780_TOO_FEW_ERRORS_MSK, x)
> +#define ADRF6780_TOO_MANY_ERRORS_MSK		BIT(13)
> +#define ADRF6780_TOO_MANY_ERRORS(x)		FIELD_PREP(ADRF6780_TOO_MANY_ERRORS_MSK, x)
> +#define ADRF6780_ADDRESS_RANGE_ERROR_MSK	BIT(12)
> +#define ADRF6780_ADDRESS_RANGE_ERROR(x)		FIELD_PREP(ADRF6780_ADDRESS_RANGE_ERROR_MSK, x)
> +
> +/* ADRF6780_REG_ENABLE Map */
> +#define ADRF6780_VGA_BUFFER_EN_MSK		BIT(8)
> +#define ADRF6780_VGA_BUFFER_EN(x)		FIELD_PREP(ADRF6780_VGA_BUFFER_EN_MSK, x)
> +#define ADRF6780_DETECTOR_EN_MSK		BIT(7)
> +#define ADRF6780_DETECTOR_EN(x)			FIELD_PREP(ADRF6780_DETECTOR_EN_MSK, x)
> +#define ADRF6780_LO_BUFFER_EN_MSK		BIT(6)
> +#define ADRF6780_LO_BUFFER_EN(x)		FIELD_PREP(ADRF6780_LO_BUFFER_EN_MSK, x)
> +#define ADRF6780_IF_MODE_EN_MSK			BIT(5)
> +#define ADRF6780_IF_MODE_EN(x)			FIELD_PREP(ADRF6780_IF_MODE_EN_MSK, x)
> +#define ADRF6780_IQ_MODE_EN_MSK			BIT(4)
> +#define ADRF6780_IQ_MODE_EN(x)			FIELD_PREP(ADRF6780_IQ_MODE_EN_MSK, x)
> +#define ADRF6780_LO_X2_EN_MSK			BIT(3)
> +#define ADRF6780_LO_X2_EN(x)			FIELD_PREP(ADRF6780_LO_X2_EN_MSK, x)
> +#define ADRF6780_LO_PPF_EN_MSK			BIT(2)
> +#define ADRF6780_LO_PPF_EN(x)			FIELD_PREP(ADRF6780_LO_PPF_EN_MSK, x)
> +#define ADRF6780_LO_EN_MSK			BIT(1)
> +#define ADRF6780_LO_EN(x)			FIELD_PREP(ADRF6780_LO_EN_MSK, x)
> +#define ADRF6780_UC_BIAS_EN_MSK			BIT(0)
> +#define ADRF6780_UC_BIAS_EN(x)			FIELD_PREP(ADRF6780_UC_BIAS_EN_MSK, x)
> +
> +/* ADRF6780_REG_LINEARIZE Map */
> +#define ADRF6780_RDAC_LINEARIZE_MSK		GENMASK(7, 0)
> +#define ADRF6780_RDAC_LINEARIZE(x)		FIELD_PREP(ADRF6780_RDAC_LINEARIZE_MSK, x)
> +
> +/* ADRF6780_REG_LO_PATH Map */
> +#define ADRF6780_LO_SIDEBAND_MSK		BIT(10)
> +#define ADRF6780_LO_SIDEBAND(x)			FIELD_PREP(ADRF6780_LO_SIDEBAND_MSK, x)
> +#define ADRF6780_Q_PATH_PHASE_ACCURACY_MSK	GENMASK(7, 4)
> +#define ADRF6780_Q_PATH_PHASE_ACCURACY(x)	FIELD_PREP(ADRF6780_Q_PATH_PHASE_ACCURACY_MSK, x)
> +#define ADRF6780_I_PATH_PHASE_ACCURACY_MSK	GENMASK(3, 0)
> +#define ADRF6780_I_PATH_PHASE_ACCURACY(x)	FIELD_PREP(ADRF6780_I_PATH_PHASE_ACCURACY_MSK, x)
> +
> +/* ADRF6780_REG_ADC_CONTROL Map */
> +#define ADRF6780_VDET_OUTPUT_SELECT_MSK		BIT(3)
> +#define ADRF6780_VDET_OUTPUT_SELECT(x)		FIELD_PREP(ADRF6780_VDET_OUTPUT_SELECT_MSK, x)
> +#define ADRF6780_ADC_START_MSK			BIT(2)
> +#define ADRF6780_ADC_START(x)			FIELD_PREP(ADRF6780_ADC_START_MSK, x)
> +#define ADRF6780_ADC_EN_MSK			BIT(1)
> +#define ADRF6780_ADC_EN(x)			FIELD_PREP(ADRF6780_ADC_EN_MSK, x)
> +#define ADRF6780_ADC_CLOCK_EN_MSK		BIT(0)
> +#define ADRF6780_ADC_CLOCK_EN(x)		FIELD_PREP(ADRF6780_ADC_CLOCK_EN_MSK, x)
> +
> +/* ADRF6780_REG_ADC_OUTPUT Map */
> +#define ADRF6780_ADC_STATUS_MSK			BIT(8)
> +#define ADRF6780_ADC_STATUS(x)			FIELD_PREP(ADRF6780_ADC_STATUS_MSK, x)
> +#define ADRF6780_ADC_VALUE_MSK			GENMASK(7, 0)
> +#define ADRF6780_ADC_VALUE(x)			FIELD_PREP(ADRF6780_ADC_VALUE_MSK, x)

Not used.  In general, just use FIELD_PREP / FIELD_GET inline rather than having extra
macros like these. That approach is simpler for reviewers to follow.

> +
> +struct adrf6780_dev {
> +	struct spi_device	*spi;
> +	struct clk		*clkin;
> +	/* Protect against concurrent accesses to the device */
> +	struct mutex		lock;
> +	bool			vga_buff_en;
> +	bool			lo_buff_en;
> +	bool			if_mode_en;
> +	bool			iq_mode_en;
> +	bool			lo_x2_en;
> +	bool			lo_ppf_en;
> +	bool			lo_en;
> +	bool			uc_bias_en;
> +	bool			lo_sideband;
> +	bool			vdet_out_en;
> +};
> +
> +static int adrf6780_spi_read(struct adrf6780_dev *dev, unsigned int reg,
> +			      unsigned int *val)
> +{
> +	int ret;
> +	unsigned int temp;
> +	struct spi_transfer t = {0};
> +	u8 data[3];
> +
> +	data[0] = 0x80 | (reg << 1);
> +	data[1] = 0x0;
> +	data[2] = 0x0;
> +
> +	t.rx_buf = &data[0];
> +	t.tx_buf = &data[0];
> +	t.len = 3;
> +
> +	ret = spi_sync_transfer(dev->spi, &t, 1);

data needs to be dma safe.

> +	if (ret < 0)
> +		return ret;
> +
> +	temp = ((data[0] | 0x80 | (reg << 1)) << 16) |
> +		(data[1] << 8) | data[2];

Ouch. That's a bit nasty, but why are you writing the reg into
it?  Looks like a get_unaligned_be24() >> 1 and a 16bit mask.
(use GENMASK(15, 0) for that to make it apparent what is happening.

> +
> +	*val = (temp >> 1) & 0xFFFF;
> +
> +	return ret;
> +}
> +
> +static int adrf6780_spi_write(struct adrf6780_dev *dev,
> +				      unsigned int reg,
> +				      unsigned int val)
> +{
> +	u8 data[3];
> +
> +	val = (val << 1);
> +
> +	data[0] = (reg << 1) | (val >> 16);
> +	data[1] = val >> 8;
> +	data[2] = val;

An opportunity for
put_unaligned_be24() with a value of (I think)

(val << 1) | (reg << 17)  


> +
> +	return spi_write(dev->spi, &data[0], 3);

Needs a dma safe buffer, which basically means it can't be on the stack.
Lots of ways of handling that, but look for __cacheline_aligned in IIO drivers
to see the one we probably use mostly commonly in IIO drivers.


> +}
> +
> +static int __adrf6780_spi_update_bits(struct adrf6780_dev *dev, unsigned int reg,
> +			       unsigned int mask, unsigned int val)
> +{
> +	int ret;
> +	unsigned int data, temp;
> +
> +	ret = adrf6780_spi_read(dev, reg, &data);
> +	if (ret < 0)

As this is ultimately getting the result of spi_sync_transfer() which never returns > 0
you can switch this to the more relaxed if (ret)  That ends up more consistent
if you are going to do return adrf6780 below.  (also only returns <= 0 but that's
not obvious given you have this check here on the equivalent read function that
hints that positive can occur.

> +		return ret;
> +
> +	temp = (data & ~mask) | (val & mask);
> +
> +	return adrf6780_spi_write(dev, reg, temp);
> +}
> +
> +static int adrf6780_spi_update_bits(struct adrf6780_dev *dev, unsigned int reg,
> +			       unsigned int mask, unsigned int val)

This is so rarely called, that I'm not sure it is worth it existing (as opposed
to just having this code inline where needed).

The naming is currently inconsistent.  adrf6780_spi_read() doesn't take the lock
but adrf6780_spi_update_bits() does. 

So drop this function and rename unlocked version to adrf6780_spi_update_bits()
 

> +{
> +	int ret;
> +
> +	mutex_lock(&dev->lock);
> +	ret = __adrf6780_spi_update_bits(dev, reg, mask, val);
> +	mutex_unlock(&dev->lock);
> +	return ret;
> +}
> +
> +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:
> +		mutex_lock(&dev->lock);
> +
> +		ret = __adrf6780_spi_update_bits(dev, ADRF6780_REG_ADC_CONTROL,
> +						ADRF6780_ADC_EN_MSK |
> +						ADRF6780_ADC_CLOCK_EN_MSK |
> +						ADRF6780_ADC_START_MSK,
> +						ADRF6780_ADC_EN(1) |
> +						ADRF6780_ADC_CLOCK_EN(1) |
> +						ADRF6780_ADC_START(1));
> +		if (ret < 0)
> +			goto exit;
> +
> +		usleep_range(200, 250);
> +
> +		ret = adrf6780_spi_read(dev, ADRF6780_REG_ADC_OUTPUT, &data);
> +		if (ret < 0)
> +			goto exit;
> +
> +		if (!(data & ADRF6780_ADC_STATUS_MSK)) {
> +			ret = -EINVAL;
> +			goto exit;
> +		}
> +
> +		ret = __adrf6780_spi_update_bits(dev, ADRF6780_REG_ADC_CONTROL,
> +						ADRF6780_ADC_START_MSK,
> +						ADRF6780_ADC_START(0));
> +		if (ret < 0)
> +			goto exit;
> +
> +		ret = adrf6780_spi_read(dev, ADRF6780_REG_ADC_OUTPUT, &data);
> +		if (ret < 0)
> +			goto exit;
> +
> +		mutex_unlock(&dev->lock);
> +
> +		*val = data & ADRF6780_ADC_VALUE_MSK;
> +
> +		return IIO_VAL_INT;
> +exit:

Having a label inside a switch like this often indicates that we should probably
have factored some code out another function.  I think that's the case here.
Introduce a function called something like
adrf6780_read_voltage() that does everything between the locks.  That way
you can unlock and return without considering if there is an error (in this outer
function).  In the inner function, all the goto stuff becomes a direct return.

> +		mutex_unlock(&dev->lock);
> +		return ret;
> +	case IIO_CHAN_INFO_SCALE:
> +		ret = adrf6780_spi_read(dev, ADRF6780_REG_LINEARIZE, &data);
> +		if (ret < 0)
> +			return ret;
> +
> +		*val = data & ADRF6780_RDAC_LINEARIZE_MSK;
> +
> +		return IIO_VAL_INT;
> +	case IIO_CHAN_INFO_PHASE:
> +		ret = adrf6780_spi_read(dev, ADRF6780_REG_LO_PATH, &data);
> +		if (ret < 0)
> +			return ret;
> +
> +		if (chan->channel2 == IIO_MOD_I)
> +			*val = data & ADRF6780_I_PATH_PHASE_ACCURACY_MSK;
> +		else
> +			*val = (data & ADRF6780_Q_PATH_PHASE_ACCURACY_MSK) >> 4;
> +
> +		return IIO_VAL_INT;
> +	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);
> +	int ret;
> +
> +	switch (info) {
> +	case IIO_CHAN_INFO_SCALE:
> +		return adrf6780_spi_write(dev, ADRF6780_REG_LINEARIZE, val);
> +	case IIO_CHAN_INFO_PHASE:
> +		if (chan->channel2 == IIO_MOD_I)

Where you have two options you are matching like here, I'd prefer to see a switch statement
(with a default that returns an error).  That makes it immediately clear there are only
two valid options.

> +			ret = adrf6780_spi_update_bits(dev, ADRF6780_REG_LO_PATH,
> +							ADRF6780_I_PATH_PHASE_ACCURACY_MSK,
> +							ADRF6780_I_PATH_PHASE_ACCURACY(val));
> +		else
> +			ret = adrf6780_spi_update_bits(dev, ADRF6780_REG_LO_PATH,
> +							ADRF6780_Q_PATH_PHASE_ACCURACY_MSK,
> +							ADRF6780_Q_PATH_PHASE_ACCURACY(val));
> +		return ret;
> +	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)
> +		return adrf6780_spi_read(dev, reg, read_val);
> +	else
> +		return adrf6780_spi_write(dev, reg, write_val);
> +}
> +
> +static const struct iio_info adrf6780_info = {
> +	.read_raw = adrf6780_read_raw,
> +	.write_raw = adrf6780_write_raw,
> +	.debugfs_reg_access = &adrf6780_reg_access,
> +};
> +
> +#define ADRF6780_CHAN(_channel) {			\
> +	.type = IIO_VOLTAGE,				\
> +	.output = 1,					\
> +	.indexed = 1,					\
> +	.channel = _channel,				\
> +	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |	\
> +		BIT(IIO_CHAN_INFO_SCALE)		\
> +}
> +
> +#define ADRF6780_CHAN_IQ(_channel, rf_comp) {			\
> +	.type = IIO_ALTVOLTAGE,					\
> +	.modified = 1,						\
> +	.output = 1,						\
> +	.indexed = 1,						\
> +	.channel2 = IIO_MOD_##rf_comp,				\
> +	.channel = _channel,					\
> +	.info_mask_separate = BIT(IIO_CHAN_INFO_PHASE)		\
> +}
> +
> +static const struct iio_chan_spec adrf6780_channels[] = {
> +	ADRF6780_CHAN(0),
> +	ADRF6780_CHAN_IQ(0, I),
> +	ADRF6780_CHAN_IQ(0, Q),
> +};
> +
> +static int adrf6780_reset(struct adrf6780_dev *dev)
> +{
> +	int ret;
> +	struct spi_device *spi = dev->spi;
> +
> +	ret = __adrf6780_spi_update_bits(dev, ADRF6780_REG_CONTROL,
> +				 ADRF6780_SOFT_RESET_MSK,
> +				 ADRF6780_SOFT_RESET(1));
> +	if (ret < 0) {
> +		dev_err(&spi->dev, "ADRF6780 SPI software reset failed.\n");
> +		return ret;
> +	}
> +
> +	ret = __adrf6780_spi_update_bits(dev, ADRF6780_REG_CONTROL,
> +				 ADRF6780_SOFT_RESET_MSK,
> +				 ADRF6780_SOFT_RESET(0));
> +	if (ret < 0) {
> +		dev_err(&spi->dev, "ADRF6780 SPI software reset disable failed.\n");
> +		return ret;
> +	}
> +
> +	return ret;

return 0; Make the value obvious where you can. we can't get here with a positive
value but that isn't clear from looking at the function.


> +}
> +
> +static int adrf6780_init(struct adrf6780_dev *dev)
> +{
> +	int ret;
> +	unsigned int chip_id, enable_reg, enable_reg_msk;
> +	struct spi_device *spi = dev->spi;
> +
> +	/* Perform a software reset */
> +	ret = adrf6780_reset(dev);
> +	if (ret < 0)
> +		return ret;
> +
> +	ret = adrf6780_spi_read(dev, ADRF6780_REG_CONTROL, &chip_id);
> +	if (ret < 0)
> +		return ret;
> +
> +	chip_id = (chip_id & ADRF6780_CHIP_ID_MSK) >> 4;

FIELD_GET()

> +	if (chip_id != ADRF6780_CHIP_ID) {
> +		dev_err(&spi->dev, "ADRF6780 Invalid Chip ID.\n");
> +		return -EINVAL;
> +	}
> +
> +	enable_reg_msk = ADRF6780_VGA_BUFFER_EN_MSK |
> +			ADRF6780_DETECTOR_EN_MSK |
> +			ADRF6780_LO_BUFFER_EN_MSK |
> +			ADRF6780_IF_MODE_EN_MSK |
> +			ADRF6780_IQ_MODE_EN_MSK |
> +			ADRF6780_LO_X2_EN_MSK |
> +			ADRF6780_LO_PPF_EN_MSK |
> +			ADRF6780_LO_EN_MSK |
> +			ADRF6780_UC_BIAS_EN_MSK;
> +
> +	enable_reg = ADRF6780_VGA_BUFFER_EN(dev->vga_buff_en) |
> +			ADRF6780_DETECTOR_EN(1) |
> +			ADRF6780_LO_BUFFER_EN(dev->lo_buff_en) |
> +			ADRF6780_IF_MODE_EN(dev->if_mode_en) |
> +			ADRF6780_IQ_MODE_EN(dev->iq_mode_en) |
> +			ADRF6780_LO_X2_EN(dev->lo_x2_en) |
> +			ADRF6780_LO_PPF_EN(dev->lo_ppf_en) |
> +			ADRF6780_LO_EN(dev->lo_en) |
> +			ADRF6780_UC_BIAS_EN(dev->uc_bias_en);
> +
> +	ret = __adrf6780_spi_update_bits(dev, ADRF6780_REG_ENABLE, enable_reg_msk, enable_reg);
> +	if (ret < 0)
> +		return ret;
> +
> +	ret = __adrf6780_spi_update_bits(dev, ADRF6780_REG_LO_PATH,
> +						ADRF6780_LO_SIDEBAND_MSK,
> +						ADRF6780_LO_SIDEBAND(dev->lo_sideband));

I mention this above, but where possible make it clear that positive values don't occur
with if (ret) rather that if (ret < 0)

That way we don't end up suggesting this function might return a positive value.

> +	if (ret < 0)
> +		return ret;
> +
> +	return __adrf6780_spi_update_bits(dev, ADRF6780_REG_ADC_CONTROL,
> +						ADRF6780_VDET_OUTPUT_SELECT_MSK,
> +						ADRF6780_VDET_OUTPUT_SELECT(dev->vdet_out_en));
> +}
> +
> +static void adrf6780_clk_disable(void *data)
> +{
> +	clk_disable_unprepare(data);
> +}
> +
> +static int adrf6780_dt_parse(struct adrf6780_dev *dev)
> +{
> +	struct spi_device *spi = dev->spi;
> +
> +	dev->vga_buff_en = of_property_read_bool(spi->dev.of_node, "adi,vga-buff-en");
generic firmware functions preferred.

See include/linux/property.h

> +	dev->lo_buff_en = of_property_read_bool(spi->dev.of_node, "adi,lo-buff-en");
> +	dev->if_mode_en = of_property_read_bool(spi->dev.of_node, "adi,if-mode-en");
> +	dev->iq_mode_en = of_property_read_bool(spi->dev.of_node, "adi,iq-mode-en");
> +	dev->lo_x2_en = of_property_read_bool(spi->dev.of_node, "adi,lo-x2-en");
> +	dev->lo_ppf_en = of_property_read_bool(spi->dev.of_node, "adi,lo-ppf-en");
> +	dev->lo_en = of_property_read_bool(spi->dev.of_node, "adi,lo-en");
> +	dev->uc_bias_en = of_property_read_bool(spi->dev.of_node, "adi,uc-bias-en");
> +	dev->lo_sideband = of_property_read_bool(spi->dev.of_node, "adi,lo-sideband");
> +	dev->vdet_out_en = of_property_read_bool(spi->dev.of_node, "adi,vdet-out-en");
> +
> +	return 0;

If there are no possible errors, then change the function to return void and
drop the error check at the caller.

> +}
> +
> +static int adrf6780_probe(struct spi_device *spi)
> +{
> +	struct iio_dev *indio_dev;
> +	struct adrf6780_dev *dev;
> +	int ret;
> +
> +	indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*dev));
> +	if (!indio_dev)
> +		return -ENOMEM;
> +
> +	dev = iio_priv(indio_dev);
> +
> +	indio_dev->info = &adrf6780_info;
> +	indio_dev->name = "adrf6780";
> +	indio_dev->channels = adrf6780_channels;
> +	indio_dev->num_channels = ARRAY_SIZE(adrf6780_channels);
> +
> +	dev->spi = spi;
> +
> +	ret = adrf6780_dt_parse(dev);
> +	if (ret < 0)
> +		return ret;
> +
> +	dev->clkin = devm_clk_get(&spi->dev, "lo_in");
> +	if (IS_ERR(dev->clkin))
> +		return PTR_ERR(dev->clkin);
> +
> +	ret = clk_prepare_enable(dev->clkin);
> +	if (ret < 0)
> +		return ret;
> +
> +	ret = devm_add_action_or_reset(&spi->dev, adrf6780_clk_disable, dev->clkin);
> +	if (ret < 0)
> +		return ret;
> +
> +	mutex_init(&dev->lock);
> +
> +	ret = adrf6780_init(dev);
> +	if (ret < 0)
> +		return ret;
> +
> +	return devm_iio_device_register(&spi->dev, indio_dev);
> +}
> +
> +static const struct spi_device_id adrf6780_id[] = {
> +	{ "adrf6780", 0 },
> +	{}
> +};
> +MODULE_DEVICE_TABLE(spi, adrf6780_id);
> +
> +static const struct of_device_id adrf6780_of_match[] = {
> +	{ .compatible = "adi,adrf6780" },
> +	{}
> +};
> +MODULE_DEVICE_TABLE(of, adrf6780_of_match);
> +
> +static struct spi_driver adrf6780_driver = {
> +	.driver = {
> +		.name = "adrf6780",
> +		.of_match_table = adrf6780_of_match,
> +	},
> +	.probe = adrf6780_probe,
> +	.id_table = adrf6780_id,
> +};
> +module_spi_driver(adrf6780_driver);
> +
> +MODULE_AUTHOR("Antoniu Miclaus <antoniu.miclaus@analog.com");
> +MODULE_DESCRIPTION("Analog Devices ADRF6780");
> +MODULE_LICENSE("GPL v2");