Re: [PATCH v4 2/2] iio: dac: Add support for external reference voltage through the regulator framework.

[Jonathan Cameron <jic23@kernel.org>]

On Mon, 21 May 2018 14:21:28 +0200
Silvan Murer <silvan.murer@gmail.com> wrote:

> Signed-off-by: Silvan Murer <silvan.murer@gmail.com>
> Reviewed-by: Lars-Peter Clausen <lars@metafoo.de>

Applied to the togreg branch of iio.git and pushed out as testing
for the autobuilders to play with it.

Thanks,

Jonathan

> ---
>  .../devicetree/bindings/iio/dac/ltc2632.txt        | 14 +++++
>  drivers/iio/dac/ltc2632.c                          | 70 +++++++++++++++++++---
>  2 files changed, 75 insertions(+), 9 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/iio/dac/ltc2632.txt b/Documentation/devicetree/bindings/iio/dac/ltc2632.txt
> index eb911e5..e0d5fea 100644
> --- a/Documentation/devicetree/bindings/iio/dac/ltc2632.txt
> +++ b/Documentation/devicetree/bindings/iio/dac/ltc2632.txt
> @@ -12,12 +12,26 @@ Required properties:
>  Property rules described in Documentation/devicetree/bindings/spi/spi-bus.txt
>  apply. In particular, "reg" and "spi-max-frequency" properties must be given.
>  
> +Optional properties:
> +	- vref-supply: Phandle to the external reference voltage supply. This should
> +	  only be set if there is an external reference voltage connected to the VREF
> +	  pin. If the property is not set the internal reference is used.
> +
>  Example:
>  
> +	vref: regulator-vref {
> +		compatible = "regulator-fixed";
> +		regulator-name = "vref-ltc2632";
> +		regulator-min-microvolt = <1250000>;
> +		regulator-max-microvolt = <1250000>;
> +		regulator-always-on;
> +	};
> +
>  	spi_master {
>  		dac: ltc2632@0 {
>  			compatible = "lltc,ltc2632-l12";
>  			reg = <0>; /* CS0 */
>  			spi-max-frequency = <1000000>;
> +			vref-supply = <&vref>; /* optional */
>  		};
>  	};
> diff --git a/drivers/iio/dac/ltc2632.c b/drivers/iio/dac/ltc2632.c
> index d322b78..9551156 100644
> --- a/drivers/iio/dac/ltc2632.c
> +++ b/drivers/iio/dac/ltc2632.c
> @@ -2,6 +2,7 @@
>   * LTC2632 Digital to analog convertors spi driver
>   *
>   * Copyright 2017 Maxime Roussin-B_langer
> + * expanded by Silvan Murer <silvan.murer@gmail.com>
>   *
>   * Licensed under the GPL-2.
>   */
> @@ -10,6 +11,7 @@
>  #include <linux/spi/spi.h>
>  #include <linux/module.h>
>  #include <linux/iio/iio.h>
> +#include <linux/regulator/consumer.h>
>  
>  #define LTC2632_DAC_CHANNELS                    2
>  
> @@ -28,7 +30,7 @@
>  /**
>   * struct ltc2632_chip_info - chip specific information
>   * @channels:		channel spec for the DAC
> - * @vref_mv:		reference voltage
> + * @vref_mv:		internal reference voltage
>   */
>  struct ltc2632_chip_info {
>  	const struct iio_chan_spec *channels;
> @@ -39,10 +41,14 @@ struct ltc2632_chip_info {
>   * struct ltc2632_state - driver instance specific data
>   * @spi_dev:			pointer to the spi_device struct
>   * @powerdown_cache_mask	used to show current channel powerdown state
> + * @vref_mv			used reference voltage (internal or external)
> + * @vref_reg		regulator for the reference voltage
>   */
>  struct ltc2632_state {
>  	struct spi_device *spi_dev;
>  	unsigned int powerdown_cache_mask;
> +	int vref_mv;
> +	struct regulator *vref_reg;
>  };
>  
>  enum ltc2632_supported_device_ids {
> @@ -90,7 +96,7 @@ static int ltc2632_read_raw(struct iio_dev *indio_dev,
>  
>  	switch (m) {
>  	case IIO_CHAN_INFO_SCALE:
> -		*val = chip_info->vref_mv;
> +		*val = st->vref_mv;
>  		*val2 = chan->scan_type.realbits;
>  		return IIO_VAL_FRACTIONAL_LOG2;
>  	}
> @@ -247,6 +253,45 @@ static int ltc2632_probe(struct spi_device *spi)
>  	chip_info = (struct ltc2632_chip_info *)
>  			spi_get_device_id(spi)->driver_data;
>  
> +	st->vref_reg = devm_regulator_get_optional(&spi->dev, "vref");
> +	if (PTR_ERR(st->vref_reg) == -ENODEV) {
> +		/* use internal reference voltage */
> +		st->vref_reg = NULL;
> +		st->vref_mv = chip_info->vref_mv;
> +
> +		ret = ltc2632_spi_write(spi, LTC2632_CMD_INTERNAL_REFER,
> +				0, 0, 0);
> +		if (ret) {
> +			dev_err(&spi->dev,
> +				"Set internal reference command failed, %d\n",
> +				ret);
> +			return ret;
> +		}
> +	} else if (IS_ERR(st->vref_reg)) {
> +		dev_err(&spi->dev,
> +				"Error getting voltage reference regulator\n");
> +		return PTR_ERR(st->vref_reg);
> +	} else {
> +		/* use external reference voltage */
> +		ret = regulator_enable(st->vref_reg);
> +		if (ret) {
> +			dev_err(&spi->dev,
> +				"enable reference regulator failed, %d\n",
> +				ret);
> +			return ret;
> +		}
> +		st->vref_mv = regulator_get_voltage(st->vref_reg) / 1000;
> +
> +		ret = ltc2632_spi_write(spi, LTC2632_CMD_EXTERNAL_REFER,
> +				0, 0, 0);
> +		if (ret) {
> +			dev_err(&spi->dev,
> +				"Set external reference command failed, %d\n",
> +				ret);
> +			return ret;
> +		}
> +	}
> +
>  	indio_dev->dev.parent = &spi->dev;
>  	indio_dev->name = dev_of_node(&spi->dev) ? dev_of_node(&spi->dev)->name
>  						 : spi_get_device_id(spi)->name;
> @@ -255,14 +300,20 @@ static int ltc2632_probe(struct spi_device *spi)
>  	indio_dev->channels = chip_info->channels;
>  	indio_dev->num_channels = LTC2632_DAC_CHANNELS;
>  
> -	ret = ltc2632_spi_write(spi, LTC2632_CMD_INTERNAL_REFER, 0, 0, 0);
> -	if (ret) {
> -		dev_err(&spi->dev,
> -			"Set internal reference command failed, %d\n", ret);
> -		return ret;
> -	}
> +	return iio_device_register(indio_dev);
> +}
> +
> +static int ltc2632_remove(struct spi_device *spi)
> +{
> +	struct iio_dev *indio_dev = spi_get_drvdata(spi);
> +	struct ltc2632_state *st = iio_priv(indio_dev);
> +
> +	iio_device_unregister(indio_dev);
> +
> +	if (st->vref_reg)
> +		regulator_disable(st->vref_reg);
>  
> -	return devm_iio_device_register(&spi->dev, indio_dev);
> +	return 0;
>  }
>  
>  static const struct spi_device_id ltc2632_id[] = {
> @@ -306,6 +357,7 @@ static struct spi_driver ltc2632_driver = {
>  		.of_match_table = of_match_ptr(ltc2632_of_match),
>  	},
>  	.probe		= ltc2632_probe,
> +	.remove		= ltc2632_remove,
>  	.id_table	= ltc2632_id,
>  };
>  module_spi_driver(ltc2632_driver);