Re: [PATCH 1/2] iio: dac: Add AD5758 support

[Peter Meerwald-Stadler]

> The AD5758 is a single channel DAC with 16-bit precision which uses the SPI
> interface that operates at clock rates up to 50MHz.
> 
> The output can be configured as voltage or current and is available on a
> single terminal.

comments below
 
> Datasheet:
> http://www.analog.com/media/en/technical-documentation/data-sheets/ad5758.pdf
> 
> Signed-off-by: Stefan Popa <stefan.popa@xxxxxxxxxx>
> ---
>  MAINTAINERS              |   7 +
>  drivers/iio/dac/Kconfig  |  10 +
>  drivers/iio/dac/Makefile |   1 +
>  drivers/iio/dac/ad5758.c | 826 +++++++++++++++++++++++++++++++++++++++++++++++
>  4 files changed, 844 insertions(+)
>  create mode 100644 drivers/iio/dac/ad5758.c
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 4b65225..1993779 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -802,6 +802,13 @@ S:	Supported
>  F:	drivers/iio/dac/ad5686*
>  F:	drivers/iio/dac/ad5696*
>  
> +ANALOG DEVICES INC AD5758 DRIVER
> +M:	Stefan Popa <stefan.popa@xxxxxxxxxx>
> +L:	linux-iio@xxxxxxxxxxxxxxx
> +W:	http://ez.analog.com/community/linux-device-drivers
> +S:	Supported
> +F:	drivers/iio/dac/ad5758.c
> +
>  ANALOG DEVICES INC AD9389B DRIVER
>  M:	Hans Verkuil <hans.verkuil@xxxxxxxxx>
>  L:	linux-media@xxxxxxxxxxxxxxx
> diff --git a/drivers/iio/dac/Kconfig b/drivers/iio/dac/Kconfig
> index 06e90de..80beb64 100644
> --- a/drivers/iio/dac/Kconfig
> +++ b/drivers/iio/dac/Kconfig
> @@ -167,6 +167,16 @@ config AD5755
>  	  To compile this driver as a module, choose M here: the
>  	  module will be called ad5755.
>  
> +config AD5758
> +	tristate "Analog Devices AD5758 DAC driver"
> +	depends on SPI_MASTER
> +	help
> +	  Say yes here to build support for Analog Devices AD5758 single channel
> +	  Digital to Analog Converter.
> +
> +	  To compile this driver as a module, choose M here: the
> +	  module will be called ad5758.
> +
>  config AD5761
>  	tristate "Analog Devices AD5761/61R/21/21R DAC driver"
>  	depends on SPI_MASTER
> diff --git a/drivers/iio/dac/Makefile b/drivers/iio/dac/Makefile
> index 57aa230..e859f2d 100644
> --- a/drivers/iio/dac/Makefile
> +++ b/drivers/iio/dac/Makefile
> @@ -16,6 +16,7 @@ obj-$(CONFIG_AD5592R_BASE) += ad5592r-base.o
>  obj-$(CONFIG_AD5592R) += ad5592r.o
>  obj-$(CONFIG_AD5593R) += ad5593r.o
>  obj-$(CONFIG_AD5755) += ad5755.o
> +obj-$(CONFIG_AD5758) += ad5758.o
>  obj-$(CONFIG_AD5761) += ad5761.o
>  obj-$(CONFIG_AD5764) += ad5764.o
>  obj-$(CONFIG_AD5791) += ad5791.o
> diff --git a/drivers/iio/dac/ad5758.c b/drivers/iio/dac/ad5758.c
> new file mode 100644
> index 0000000..0a26b9d
> --- /dev/null
> +++ b/drivers/iio/dac/ad5758.c
> @@ -0,0 +1,826 @@
> +// SPDX-License-Identifier: GPL-2.0+
> +/*
> + * AD5758 Digital to analog converters driver
> + *
> + * Copyright 2018 Analog Devices Inc.
> + */
> +
> +#include <linux/fs.h>
> +#include <linux/device.h>
> +#include <linux/module.h>
> +#include <linux/kernel.h>
> +#include <linux/slab.h>
> +#include <linux/sysfs.h>
> +#include <linux/spi/spi.h>
> +#include <linux/delay.h>
> +
> +#include <linux/iio/iio.h>
> +#include <linux/iio/sysfs.h>
> +#include <linux/property.h>
> +
> +/* AD5758 registers definition */
> +#define AD5758_NOP					0x00
> +#define AD5758_DAC_INPUT				0x01
> +#define AD5758_DAC_OUTPUT				0x02
> +#define AD5758_CLEAR_CODE				0x03
> +#define AD5758_USER_GAIN				0x04
> +#define AD5758_USER_OFFSET				0x05
> +#define AD5758_DAC_CONFIG				0x06
> +#define AD5758_SW_LDAC					0x07
> +#define AD5758_KEY					0x08
> +#define AD5758_GP_CONFIG1				0x09
> +#define AD5758_GP_CONFIG2				0x0A
> +#define AD5758_DCDC_CONFIG1				0x0B
> +#define AD5758_DCDC_CONFIG2				0x0C
> +#define AD5758_WDT_CONFIG				0x0F
> +#define AD5758_DIGITAL_DIAG_CONFIG			0x10
> +#define AD5758_ADC_CONFIG				0x11
> +#define AD5758_FAULT_PIN_CONFIG				0x12
> +#define AD5758_TWO_STAGE_READBACK_SELECT		0x13
> +#define AD5758_DIGITAL_DIAG_RESULTS			0x14
> +#define AD5758_ANALOG_DIAG_RESULTS			0x15
> +#define AD5758_STATUS					0x16
> +#define AD5758_CHIP_ID					0x17
> +#define AD5758_FREQ_MONITOR				0x18
> +#define AD5758_DEVICE_ID_0				0x19
> +#define AD5758_DEVICE_ID_1				0x1A
> +#define AD5758_DEVICE_ID_2				0x1B
> +#define AD5758_DEVICE_ID_3				0x1C
> +
> +/* AD5758_DAC_CONFIG */
> +#define AD5758_DAC_CONFIG_RANGE_MSK			GENMASK(3, 0)
> +#define AD5758_DAC_CONFIG_RANGE_MODE(x)			(((x) & 0xF) << 0)
> +#define AD5758_DAC_CONFIG_OVRNG_EN_MSK			BIT(4)
> +#define AD5758_DAC_CONFIG_OVRNG_EN_MODE(x)		(((x) & 0x1) << 4)
> +#define AD5758_DAC_CONFIG_INT_EN_MSK			BIT(5)
> +#define AD5758_DAC_CONFIG_INT_EN_MODE(x)		(((x) & 0x1) << 5)
> +#define AD5758_DAC_CONFIG_OUT_EN_MSK			BIT(6)
> +#define AD5758_DAC_CONFIG_OUT_EN_MODE(x)		(((x) & 0x1) << 6)
> +#define AD5758_DAC_CONFIG_RSET_EXT_EN_MSK		BIT(7)
> +#define AD5758_DAC_CONFIG_RSET_EXT_EN_MODE(x)		(((x) & 0x1) << 7)
> +#define AD5758_DAC_CONFIG_SR_EN_MSK			BIT(8)
> +#define AD5758_DAC_CONFIG_SR_EN_MODE(x)			(((x) & 0x1) << 8)
> +#define AD5758_DAC_CONFIG_SR_CLOCK_MSK			GENMASK(12, 9)
> +#define AD5758_DAC_CONFIG_SR_CLOCK_MODE(x)		(((x) & 0xF) << 9)
> +#define AD5758_DAC_CONFIG_SR_STEP_MSK			GENMASK(15, 13)
> +#define AD5758_DAC_CONFIG_SR_STEP_MODE(x)		(((x) & 0x7) << 13)
> +
> +/* AD5758_KEY */
> +#define AD5758_KEY_CODE_RESET_1				0x15FA
> +#define AD5758_KEY_CODE_RESET_2				0xAF51
> +#define AD5758_KEY_CODE_SINGLE_ADC_CONV			0x1ADC
> +#define AD5758_KEY_CODE_RESET_WDT			0x0D06
> +#define AD5758_KEY_CODE_CALIB_MEM_REFRESH		0xFCBA
> +
> +/* AD5758_DCDC_CONFIG1 */
> +#define AD5758_DCDC_CONFIG1_DCDC_VPROG_MSK		GENMASK(4, 0)
> +#define AD5758_DCDC_CONFIG1_DCDC_VPROG_MODE(x)		(((x) & 0x1F) << 0)
> +#define AD5758_DCDC_CONFIG1_DCDC_MODE_MSK		GENMASK(6, 5)
> +#define AD5758_DCDC_CONFIG1_DCDC_MODE_MODE(x)		(((x) & 0x3) << 5)
> +#define AD5758_DCDC_CONFIG1_FAULT_PROT_SW_EN_MSK	BIT(7)
> +#define AD5758_DCDC_CONFIG1_FAULT_PROT_SW_EN_MODE(x)	(((x) & 0x1) << 7)
> +
> +/* AD5758_DCDC_CONFIG2 */
> +#define AD5758_DCDC_CONFIG2_ILIMIT_MSK			GENMASK(3, 1)
> +#define AD5758_DCDC_CONFIG2_ILIMIT_MODE(x)		(((x) & 0x7) << 1)
> +#define AD5758_DCDC_CONFIG2_ADC_CONTROL_DIAG_MSK	GENMASK(5, 4)
> +#define AD5758_DCDC_CONFIG2_ADC_CONTROL_DIAG_MODE(x)	(((x) & 0x3) << 4)
> +#define AD5758_DCDC_CONFIG2_VIOUT_PULLDOWN_EN_MSK	BIT(6)
> +#define AD5758_DCDC_CONFIG2_VIOUT_PULLDOWN_EN_MODE(x)	(((x) & 0x1) << 6)
> +#define AD5758_DCDC_CONFIG2_SHORT_DEGLITCH_MSK		BIT(7)
> +#define AD5758_DCDC_CONFIG2_SHORT_DEGLITCH_MODE(x)	(((x) & 0x1) << 7)
> +#define AD5758_DCDC_CONFIG2_READ_COMP_DIS_MSK		BIT(10)
> +#define AD5758_DCDC_CONFIG2_READ_COMP_DIS_MODE(x)	(((x) & 0x1) << 10)
> +#define AD5758_DCDC_CONFIG2_INTR_SAT_3WI_MSK		BIT(11)
> +#define AD5758_DCDC_CONFIG2_BUSY_3WI_MSK		BIT(12)
> +
> +/* AD5758_DIGITAL_DIAG_RESULTS */
> +#define AD5758_DIG_DIAG_RES_CAL_MEM_UNREFRESHED_MSK	BIT(15)
> +
> +#define AD5758_REG_WRITE(x)	((0x80) | ((x) & 0x1F))

parenthesis around 0x80 not strictly needed

> +
> +/* x^8 + x^2 + x^1 + x^0 */
> +#define AD5758_CRC8_POLY	0x07
> +
> +/**
> + * struct ad5758_state - driver instance specific data
> + * @spi:	spi_device
> + * @dc_dc_mode:	variable which stores the mode of operation

the documentation misses several fields

> + * @out_range:	variable which stores the output range
> + * @pwr_down:	variable which contains whether a channel is powered down or not

sounds like it should be bool?

> + * @data:	spi transfer buffers
> + */
> +
> +struct ad5758_state {
> +	struct spi_device *spi;
> +	struct mutex lock;
> +	unsigned int dc_dc_mode;
> +	unsigned int dc_dc_ilim;
> +	unsigned int sr_config[3];
> +	unsigned int out_range;
> +	unsigned int pwr_down;
> +
> +	/*
> +	 * DMA (thus cache coherency maintenance) requires the
> +	 * transfer buffers to live in their own cache lines.
> +	 */
> +
> +	union {
> +		__be32 d32;
> +		u8 d8[4];
> +	} data[3] ____cacheline_aligned;
> +};
> +
> +enum ad5758_output_range {
> +	AD5758_RANGE_0V_5V,
> +	AD5758_RANGE_0V_10V,
> +	AD5758_RANGE_PLUSMINUS_5V,
> +	AD5758_RANGE_PLUSMINUS_10V,
> +	AD5758_RANGE_0mA_20mA = 8,
> +	AD5758_RANGE_0mA_24mA,
> +	AD5758_RANGE_4mA_24mA,
> +	AD5758_RANGE_PLUSMINUS_20mA,
> +	AD5758_RANGE_PLUSMINUS_24mA,
> +	AD5758_RANGE_MINUS_1mA_PLUS_22mA,
> +};
> +
> +enum ad5758_dc_dc_mode {
> +	AD5758_DCDC_MODE_POWER_OFF,
> +	AD5758_DCDC_MODE_DPC_CURRENT,
> +	AD5758_DCDC_MODE_DPC_VOLTAGE,
> +	AD5758_DCDC_MODE_PPC_CURRENT,
> +};
> +
> +struct ad5758_range {
> +	int reg;
> +	int min;
> +	int max;
> +};
> +
> +static const struct ad5758_range ad5758_min_max_table[] = {
> +	{ AD5758_RANGE_0V_5V, 0, 5000 },
> +	{ AD5758_RANGE_0V_10V, 0, 10000 },
> +	{ AD5758_RANGE_PLUSMINUS_5V, -5000, 5000 },
> +	{ AD5758_RANGE_PLUSMINUS_10V, -10000, 10000 },
> +	{ AD5758_RANGE_0mA_20mA, 0, 20},
> +	{ AD5758_RANGE_0mA_24mA, 0, 24 },
> +	{ AD5758_RANGE_4mA_24mA, 4, 24 },
> +	{ AD5758_RANGE_PLUSMINUS_20mA, -20, 20 },
> +	{ AD5758_RANGE_PLUSMINUS_24mA, -24, 24 },
> +	{ AD5758_RANGE_MINUS_1mA_PLUS_22mA, -1, 22 },
> +};
> +
> +static const int ad5758_slew_rate_clk[16] = {
> +	240000, 200000, 150000, 128000, 64000, 32000, 16000, 8000, 4000, 2000,
> +	1000, 512, 256, 128, 64, 16
> +};
> +
> +static const int ad5758_slew_rate_step[8] = {
> +	4, 12, 64, 120, 256, 500, 1820, 2048
> +};
> +
> +static const int ad5758_dc_dc_ilimt[6] = {

maybe ad5758_dc_dc_ilim? consistent with the attribute in ad5758_state 
(dc_dc_ilim)

> +	150, 200, 250, 300, 350, 400
> +};
> +
> +static int ad5758_spi_reg_read(struct ad5758_state *st, unsigned int addr)
> +{
> +	struct spi_transfer t[] = {
> +		{
> +			.tx_buf = &st->data[0].d8[0],
> +			.len = 4,
> +			.cs_change = 1,
> +		}, {
> +			.tx_buf = &st->data[1].d8[0],
> +			.rx_buf = &st->data[2].d8[0],
> +			.len = 4,
> +		},
> +	};
> +	int ret;
> +
> +	st->data[0].d32 = cpu_to_be32(
> +		(AD5758_REG_WRITE(AD5758_TWO_STAGE_READBACK_SELECT) << 24) |
> +		(addr << 8));
> +	st->data[1].d32 = cpu_to_be32(AD5758_REG_WRITE(AD5758_NOP) << 24);
> +
> +	ret = spi_sync_transfer(st->spi, t, ARRAY_SIZE(t));
> +	if (ret < 0)
> +		return ret;
> +
> +	return (be32_to_cpu(st->data[2].d32) >> 8) & 0xFFFF;
> +}
> +
> +static int ad5758_spi_reg_write(struct ad5758_state *st,
> +				unsigned int addr,
> +				unsigned int val)
> +{
> +	st->data[0].d32 = cpu_to_be32((AD5758_REG_WRITE(addr) << 24) |
> +				      ((val & 0xFFFF) << 8));
> +
> +	return spi_write(st->spi, &st->data[0].d8[0], 4);

wouldn't it be clearer to write
return spi_write(st->spi, &st->data[0].d32, sizeof(st->data[0].d32));

> +}
> +
> +static int ad5758_spi_write_mask(struct ad5758_state *st,
> +				 unsigned int addr,
> +				 unsigned long int mask,
> +				 unsigned int val)
> +{
> +	int regval;
> +
> +	regval = ad5758_spi_reg_read(st, addr);
> +	if (regval < 0)
> +		return regval;
> +
> +	regval &= ~mask;
> +	regval |= val;
> +
> +	return ad5758_spi_reg_write(st, addr, regval);
> +}
> +
> +static int ad5758_get_array_index(const int *array, unsigned int size, int val)
> +{
> +	int i;
> +
> +	for (i = 0; i < size; i++) {
> +		if (val == array[i])
> +			return i;
> +	}
> +
> +	return -EINVAL;
> +}
> +
> +static int ad5758_wait_for_task_complete(struct ad5758_state *st,
> +					 unsigned int reg,
> +					 unsigned int mask)
> +{
> +	unsigned int timeout;
> +	int ret;
> +
> +	timeout = 4;
> +	do {
> +		ret = ad5758_spi_reg_read(st, reg);
> +		if (ret < 0)
> +			return ret;
> +
> +		if (!(ret & mask))
> +			return 0;
> +
> +		mdelay(1);
> +	} while (--timeout);
> +
> +	dev_err(&st->spi->dev,
> +		"Error reading bit 0x%x in 0x%x register\n", mask, reg);
> +
> +	return -EIO;
> +}
> +
> +static int ad5758_calib_mem_refresh(struct ad5758_state *st)
> +{
> +	int ret;
> +
> +	ret = ad5758_spi_reg_write(st, AD5758_KEY,
> +				   AD5758_KEY_CODE_CALIB_MEM_REFRESH);
> +
no newline here

> +	if (ret < 0) {
> +		dev_err(&st->spi->dev,
> +			"Failed to initiate a calibration memory refresh\n");
> +		return ret;
> +	}
> +
> +	/* Wait to allow time for the internal calibrations to complete */
> +	return ad5758_wait_for_task_complete(st, AD5758_DIGITAL_DIAG_RESULTS,
> +				AD5758_DIG_DIAG_RES_CAL_MEM_UNREFRESHED_MSK);
> +}
> +
> +static int ad5758_soft_reset(struct ad5758_state *st)
> +{
> +	int ret;
> +
> +	ret = ad5758_spi_reg_write(st, AD5758_KEY, AD5758_KEY_CODE_RESET_1);
> +	if (ret < 0)
> +		return ret;
> +
> +	ret = ad5758_spi_reg_write(st, AD5758_KEY, AD5758_KEY_CODE_RESET_2);
> +
> +	mdelay(1);
> +
> +	return ret;
> +}
> +
> +static int ad5758_set_dc_dc_conv_mode(struct ad5758_state *st,
> +				      unsigned int mode)

mode is more like u8?

or can the enum ad5758_dc_dc_mode be used here?

> +{
> +	int ret;
> +
> +	ret = ad5758_spi_write_mask(st, AD5758_DCDC_CONFIG1,
> +				    AD5758_DCDC_CONFIG1_DCDC_MODE_MSK,
> +				    AD5758_DCDC_CONFIG1_DCDC_MODE_MODE(mode));
> +	if (ret < 0)
> +		return ret;
> +
> +	/*
> +	 * Poll the BUSY_3WI bit in the DCDC_CONFIG2 register until it is 0.
> +	 * This allows the 3-wire interface communication to complete.
> +	 */
> +	ret = ad5758_wait_for_task_complete(st, AD5758_DCDC_CONFIG2,
> +					    AD5758_DCDC_CONFIG2_BUSY_3WI_MSK);
> +	if (ret < 0)
> +		return ret;

maybe a helper function that combines spi_write_mask() and 
wait_for_task_complete()?

> +
> +	st->dc_dc_mode = mode;
> +
> +	return ret;
> +}
> +
> +static int ad5758_set_dc_dc_ilim(struct ad5758_state *st, unsigned int ilim)
> +{
> +	int ret;
> +
> +	ret = ad5758_spi_write_mask(st, AD5758_DCDC_CONFIG2,
> +				    AD5758_DCDC_CONFIG2_ILIMIT_MSK,
> +				    AD5758_DCDC_CONFIG2_ILIMIT_MODE(ilim));
> +	if (ret < 0)
> +		return ret;
> +	/*
> +	 * Poll the BUSY_3WI bit in the DCDC_CONFIG2 register until it is 0.
> +	 * This allows the 3-wire interface communication to complete.
> +	 */
> +	return ad5758_wait_for_task_complete(st, AD5758_DCDC_CONFIG2,
> +					     AD5758_DCDC_CONFIG2_BUSY_3WI_MSK);
> +}
> +
> +static int ad5758_slew_rate_config(struct ad5758_state *st,
> +				   unsigned int enable,
> +				   unsigned int sr_clk,
> +				   unsigned int sr_step)
> +{
> +	unsigned int mode;
> +	unsigned long int mask;
> +	int ret;
> +
> +	mask = (AD5758_DAC_CONFIG_SR_EN_MSK |
> +	       AD5758_DAC_CONFIG_SR_CLOCK_MSK |
> +	       AD5758_DAC_CONFIG_SR_STEP_MSK);

parenthesis not needed

> +
> +	mode = (AD5758_DAC_CONFIG_SR_EN_MODE(enable) |
> +		AD5758_DAC_CONFIG_SR_CLOCK_MODE(sr_clk) |
> +		AD5758_DAC_CONFIG_SR_STEP_MODE(sr_step));

parenthesis not needed

> +
> +	ret = ad5758_spi_write_mask(st, AD5758_DAC_CONFIG, mask, mode);
> +	if (ret < 0)
> +		return ret;
> +
> +	/* Wait to allow time for the internal calibrations to complete */
> +	return ad5758_wait_for_task_complete(st, AD5758_DIGITAL_DIAG_RESULTS,
> +				AD5758_DIG_DIAG_RES_CAL_MEM_UNREFRESHED_MSK);
> +}
> +
> +static int ad5758_set_out_range(struct ad5758_state *st, unsigned int range)
> +{
> +	int ret;
> +
> +	ret = ad5758_spi_write_mask(st, AD5758_DAC_CONFIG,
> +				    AD5758_DAC_CONFIG_RANGE_MSK,
> +				    AD5758_DAC_CONFIG_RANGE_MODE(
> +					    ad5758_min_max_table[range].reg));
> +	if (ret < 0)
> +		return ret;
> +
> +	/* Wait to allow time for the internal calibrations to complete */
> +	ret =  ad5758_wait_for_task_complete(st, AD5758_DIGITAL_DIAG_RESULTS,
> +				AD5758_DIG_DIAG_RES_CAL_MEM_UNREFRESHED_MSK);
> +	if (ret < 0)
> +		return ret;
> +
> +	st->out_range = range;
> +
> +	return ret;
> +}
> +
> +static int ad5758_fault_prot_switch_en(struct ad5758_state *st,
> +				       unsigned char enable)

enable could be bool?

> +{
> +	int ret;
> +
> +	ret = ad5758_spi_write_mask(st, AD5758_DCDC_CONFIG1,
> +			AD5758_DCDC_CONFIG1_FAULT_PROT_SW_EN_MSK,
> +			AD5758_DCDC_CONFIG1_FAULT_PROT_SW_EN_MODE(enable));
> +	if (ret < 0)
> +		return ret;
> +	/*
> +	 * Poll the BUSY_3WI bit in the DCDC_CONFIG2 register until it is 0.
> +	 * This allows the 3-wire interface communication to complete.
> +	 */
> +	return ad5758_wait_for_task_complete(st, AD5758_DCDC_CONFIG2,
> +					     AD5758_DCDC_CONFIG2_BUSY_3WI_MSK);
> +}
> +
> +static int ad5758_internal_buffers_en(struct ad5758_state *st,
> +				      unsigned char enable)

enable could be bool?

> +{
> +	int ret;
> +
> +	ret = ad5758_spi_write_mask(st, AD5758_DAC_CONFIG,
> +				    AD5758_DAC_CONFIG_INT_EN_MSK,
> +				    AD5758_DAC_CONFIG_INT_EN_MODE(enable));
> +	if (ret < 0)
> +		return ret;
> +
> +	/* Wait to allow time for the internal calibrations to complete */
> +	return ad5758_wait_for_task_complete(st, AD5758_DIGITAL_DIAG_RESULTS,
> +				AD5758_DIG_DIAG_RES_CAL_MEM_UNREFRESHED_MSK);
> +}
> +
> +static int ad5758_reg_access(struct iio_dev *indio_dev,
> +			     unsigned int reg,
> +			     unsigned int writeval,
> +			     unsigned int *readval)
> +{
> +	struct ad5758_state *st = iio_priv(indio_dev);
> +	int ret;
> +
> +	mutex_lock(&st->lock);
> +	if (readval == NULL) {
> +		ret =  ad5758_spi_reg_write(st, reg, writeval);
> +	} else {
> +		ret = ad5758_spi_reg_read(st, reg);
> +		if (ret < 0)

mutex_unlock()?

> +			return ret;
> +
> +		*readval = ret;
> +		ret = 0;
> +	}
> +	mutex_unlock(&st->lock);
> +
> +	return ret;
> +}
> +
> +static int ad5758_read_raw(struct iio_dev *indio_dev,
> +			   struct iio_chan_spec const *chan,
> +			   int *val, int *val2, long info)
> +{
> +	struct ad5758_state *st = iio_priv(indio_dev);
> +	int max, min, ret;
> +
> +	switch (info) {
> +	case IIO_CHAN_INFO_RAW:
> +		mutex_lock(&st->lock);
> +		ret = ad5758_spi_reg_read(st, AD5758_DAC_INPUT);

could move the mutex_unlock() to here?

> +		if (ret < 0) {
> +			mutex_unlock(&st->lock);
> +			return ret;
> +		}
> +
> +		*val = ret;
> +		mutex_unlock(&st->lock);
> +		return IIO_VAL_INT;
> +	case IIO_CHAN_INFO_SCALE:
> +		min = ad5758_min_max_table[st->out_range].min;
> +		max = ad5758_min_max_table[st->out_range].max;
> +		*val = max - min;
> +		*val2 = chan->scan_type.realbits;
> +		return IIO_VAL_FRACTIONAL_LOG2;
> +	default:
> +		return -EINVAL;
> +	}
> +

not reachable

> +	return -EINVAL;
> +}
> +
> +static int ad5758_write_raw(struct iio_dev *indio_dev,
> +			    struct iio_chan_spec const *chan,
> +			    int val, int val2, long info)
> +{
> +	struct ad5758_state *st = iio_priv(indio_dev);
> +	int ret;
> +
> +	switch (info) {
> +	case IIO_CHAN_INFO_RAW:
> +		mutex_lock(&st->lock);
> +		ret = ad5758_spi_reg_write(st, AD5758_DAC_INPUT, val);
> +		mutex_unlock(&st->lock);

return directly

> +		break;
> +	default:
> +		ret = -EINVAL;
> +		break;

return directly

> +	}
> +
> +	return ret;
> +}
> +
> +static ssize_t ad5758_read_powerdown(struct iio_dev *indio_dev,
> +				     uintptr_t priv,
> +				     const struct iio_chan_spec *chan,
> +				     char *buf)
> +{
> +	struct ad5758_state *st = iio_priv(indio_dev);
> +
> +	return sprintf(buf, "%d\n", st->pwr_down);
> +}
> +
> +static ssize_t ad5758_write_powerdown(struct iio_dev *indio_dev,
> +				      uintptr_t priv,
> +				      struct iio_chan_spec const *chan,
> +				      const char *buf, size_t len)
> +{
> +	struct ad5758_state *st = iio_priv(indio_dev);
> +	bool pwr_down;
> +	unsigned int dcdc_config1_mode, dc_dc_mode, dac_config_mode, val;
> +	unsigned long int dcdc_config1_msk, dac_config_msk;
> +	int ret;
> +
> +	ret = strtobool(buf, &pwr_down);
> +	if (ret)
> +		return ret;
> +
> +	mutex_lock(&st->lock);
> +	if (pwr_down) {
> +		dc_dc_mode = AD5758_DCDC_MODE_POWER_OFF;
> +		val = 0;
> +	} else {
> +		dc_dc_mode = st->dc_dc_mode;
> +		val = 1;
> +	}
> +
> +	dcdc_config1_mode = (AD5758_DCDC_CONFIG1_DCDC_MODE_MODE(dc_dc_mode) |
> +			     AD5758_DCDC_CONFIG1_FAULT_PROT_SW_EN_MODE(val));
> +	dcdc_config1_msk = (AD5758_DCDC_CONFIG1_DCDC_MODE_MSK |
> +			    AD5758_DCDC_CONFIG1_FAULT_PROT_SW_EN_MSK);
> +
> +	ret = ad5758_spi_write_mask(st, AD5758_DCDC_CONFIG1,
> +				    dcdc_config1_msk,
> +				    dcdc_config1_mode);
> +	if (ret < 0)
> +		goto err_unlock;
> +
> +	dac_config_mode = (AD5758_DAC_CONFIG_OUT_EN_MODE(val) |
> +			   AD5758_DAC_CONFIG_INT_EN_MODE(val));
> +	dac_config_msk =  (AD5758_DAC_CONFIG_OUT_EN_MSK |
> +			   AD5758_DAC_CONFIG_INT_EN_MSK);
> +
> +	ret = ad5758_spi_write_mask(st, AD5758_DAC_CONFIG,
> +				    dac_config_msk,
> +				    dac_config_mode);
> +	if (ret < 0)
> +		goto err_unlock;
> +
> +	st->pwr_down = pwr_down;
> +
> +err_unlock:
> +	mutex_unlock(&st->lock);
> +
> +	return ret ? ret : len;
> +}
> +
> +static const struct iio_info ad5758_info = {
> +	.read_raw = ad5758_read_raw,
> +	.write_raw = ad5758_write_raw,
> +	.debugfs_reg_access = &ad5758_reg_access,
> +};
> +
> +static const struct iio_chan_spec_ext_info ad5758_ext_info[] = {
> +	{
> +		.name = "powerdown",
> +		.read = ad5758_read_powerdown,
> +		.write = ad5758_write_powerdown,
> +		.shared = IIO_SEPARATE,
> +	},
> +	{ },
> +};
> +
> +static const struct iio_chan_spec ad5758_channels[] = {
> +	{
> +		.type = IIO_VOLTAGE,
> +		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
> +		.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),
> +		.indexed = 1,
> +		.output = 1,
> +		.channel = 0,

no need for .channel = 0

> +		.scan_index = 0,

buffered mode not supported, hence no .scan_type, .scan_index necessary

> +		.scan_type = {
> +			.sign = 'u',
> +			.realbits = 16,
> +			.storagebits = 32,
> +			.shift = 0,
> +			.endianness = IIO_BE,
> +		},
> +		.ext_info = ad5758_ext_info,
> +	},
> +};
> +
> +static int ad5758_crc_disable(struct ad5758_state *st)
> +{
> +	st->data[0].d32 =
> +		cpu_to_be32(
> +		(AD5758_REG_WRITE(AD5758_DIGITAL_DIAG_CONFIG) << 24) | 0x5C3A);
> +
> +	return spi_write(st->spi, &st->data[0].d8[0], 4);
> +}
> +
> +static void ad5758_parse_dt(struct ad5758_state *st)
> +{
> +	unsigned int i, tmp, tmparray[3];
> +	int index;
> +
> +	st->dc_dc_ilim = 150;
> +	if (!device_property_read_u32(&st->spi->dev,
> +				      "adi,dc-dc-ilim", &tmp)) {
> +		index = ad5758_get_array_index(ad5758_dc_dc_ilimt,
> +					ARRAY_SIZE(ad5758_dc_dc_ilimt), tmp);
> +		if (index < 0)
> +			dev_warn(&st->spi->dev,
> +				 "dc-dc-ilim out of range using default");

a comma after range, i.e. "dc-dc-ilim out of range, using default", maybe 
even state what the default is

\n missing

> +		else
> +			st->dc_dc_ilim = index;
> +	} else {
> +		dev_dbg(&st->spi->dev,
> +			 "Missing \"dc-dc-ilim\" property, using default\n");
> +	}
> +
> +	st->dc_dc_mode = AD5758_DCDC_MODE_DPC_VOLTAGE;
> +	if (device_property_read_u32(&st->spi->dev, "adi,dc-dc-mode",
> +				     &st->dc_dc_mode))
> +		dev_dbg(&st->spi->dev,
> +			"Missing \"dc-dc-mode\" property, using DPC_VOLTAGE\n");
> +
> +	/* 0 V to 5 V voltage range */
> +	st->out_range = 0;
> +	if (!device_property_read_u32(&st->spi->dev, "adi,range", &tmp)) {
> +		for (i = 0; i < ARRAY_SIZE(ad5758_min_max_table); i++) {
> +			if (tmp == ad5758_min_max_table[i].reg) {
> +				st->out_range = i;
> +				break;
> +			}
> +		}
> +
> +		if (i == ARRAY_SIZE(ad5758_min_max_table))
> +			dev_warn(&st->spi->dev, "range invalid, using default");

\n missing

> +	} else {
> +		dev_dbg(&st->spi->dev,
> +			"Missing \"range\" property, using default\n");
> +	}
> +
> +	st->sr_config[0] = 1;
> +	st->sr_config[1] = 16000;
> +	st->sr_config[2] = 4;
> +	if (!device_property_read_u32_array(&st->spi->dev, "adi,slew",
> +					    tmparray, 3)) {
> +		st->sr_config[0] = tmparray[0];
> +
> +		index = ad5758_get_array_index(ad5758_slew_rate_clk,
> +					       ARRAY_SIZE(ad5758_slew_rate_clk),
> +					       tmparray[1]);
> +
> +		if (index < 0)
> +			dev_warn(&st->spi->dev,
> +				"slew rate clock out of range, using default");

\n missing

> +		else
> +			st->sr_config[1] = index;
> +
> +		index = ad5758_get_array_index(ad5758_slew_rate_step,
> +					ARRAY_SIZE(ad5758_slew_rate_step),
> +					tmparray[2]);
> +
> +		if (index < 0)
> +			dev_warn(&st->spi->dev,
> +				"slew rate step out of range, using default");

\n missing

> +		else
> +			st->sr_config[2] = index;
> +	} else {
> +		dev_dbg(&st->spi->dev,
> +			 "Missing \"slew\" property, using default\n");
> +	}
> +}
> +
> +static int ad5758_init(struct ad5758_state *st)
> +{
> +	int regval, ret;
> +
> +	ad5758_parse_dt(st);
> +
> +	/* Disable CRC checks */
> +	ret = ad5758_crc_disable(st);
> +	if (ret < 0)
> +		return ret;
> +
> +	/* Perform a software reset */
> +	ret = ad5758_soft_reset(st);
> +	if (ret < 0)
> +		return ret;
> +
> +	/* Disable CRC checks */
> +	ret = ad5758_crc_disable(st);
> +	if (ret < 0)
> +		return ret;
> +
> +	/* Perform a calibration memory refresh */
> +	ret = ad5758_calib_mem_refresh(st);
> +	if (ret < 0)
> +		return ret;
> +
> +	regval = ad5758_spi_reg_read(st, AD5758_DIGITAL_DIAG_RESULTS);
> +	if (regval < 0)
> +		return regval;
> +
> +	/* Clear all the error flags */
> +	ret = ad5758_spi_reg_write(st, AD5758_DIGITAL_DIAG_RESULTS, regval);
> +	if (ret < 0)
> +		return ret;
> +
> +	/* Set the dc-to-dc current limit */
> +	ret = ad5758_set_dc_dc_ilim(st, st->dc_dc_ilim);
> +	if (ret < 0)
> +		return ret;
> +
> +	/* Configure the dc-to-dc controller mode */
> +	ret = ad5758_set_dc_dc_conv_mode(st, st->dc_dc_mode);
> +	if (ret < 0)
> +		return ret;
> +
> +	/* Configure the output range */
> +	ret = ad5758_set_out_range(st, st->out_range);
> +	if (ret < 0)
> +		return ret;
> +
> +	/* Enable Slew Rate Control, set the slew rate clock and step */
> +	ret = ad5758_slew_rate_config(st, st->sr_config[0],
> +				      st->sr_config[1], st->sr_config[2]);
> +	if (ret < 0)
> +		return ret;
> +
> +	/* Enable the VIOUT fault protection switch (FPS is closed) */
> +	ret = ad5758_fault_prot_switch_en(st, 1);
> +	if (ret < 0)
> +		return ret;
> +
> +	/* Power up the DAC and internal (INT) amplifiers */
> +	ret = ad5758_internal_buffers_en(st, 1);
> +	if (ret < 0)
> +		return ret;
> +
> +	/* Enable VIOUT */
> +	ret = ad5758_spi_write_mask(st, AD5758_DAC_CONFIG,
> +				    AD5758_DAC_CONFIG_OUT_EN_MSK,
> +				    AD5758_DAC_CONFIG_OUT_EN_MODE(1));

return directly, i.e.
return ad5758_spi...

> +
> +	return ret;
> +}
> +
> +static int ad5758_probe(struct spi_device *spi)
> +{
> +	struct ad5758_state *st;
> +	struct iio_dev *indio_dev;
> +	int ret;
> +
> +	indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*st));
> +	if (!indio_dev)
> +		return -ENOMEM;
> +
> +	st = iio_priv(indio_dev);
> +	spi_set_drvdata(spi, indio_dev);
> +
> +	st->spi = spi;
> +
> +	indio_dev->dev.parent = &spi->dev;
> +	indio_dev->name = spi_get_device_id(spi)->name;
> +	indio_dev->info = &ad5758_info;
> +	indio_dev->modes = INDIO_DIRECT_MODE;
> +	indio_dev->channels = ad5758_channels;
> +	indio_dev->num_channels = ARRAY_SIZE(ad5758_channels);
> +
> +	mutex_init(&st->lock);
> +
> +	ret = ad5758_init(st);
> +	if (ret < 0) {
> +		dev_err(&spi->dev, "AD5758 init failed\n");
> +		return ret;
> +	}
> +
> +	ret = iio_device_register(indio_dev);
> +	if (ret) {
> +		dev_err(&spi->dev, "Failed to register iio device\n");

is the message really necessary/likely?

> +		return ret;
> +	}
> +
> +	return 0;
> +}
> +
> +static const struct spi_device_id ad5758_id[] = {
> +	{ "ad5758", 0 },
> +	{}
> +};
> +MODULE_DEVICE_TABLE(spi, ad5758_id);
> +
> +static struct spi_driver ad5758_driver = {
> +	.driver = {
> +		.name = KBUILD_MODNAME,
> +	},
> +	.probe = ad5758_probe,
> +	.id_table = ad5758_id,
> +};
> +
> +module_spi_driver(ad5758_driver);
> +
> +MODULE_AUTHOR("Stefan Popa <stefan.popa@xxxxxxxxxx>");
> +MODULE_DESCRIPTION("Analog Devices AD5758 DAC");
> +MODULE_LICENSE("GPL v2");
> 

-- 

Peter Meerwald-Stadler
Mobile: +43 664 24 44 418