Re: [PATCH 1/3] iio: dac: mcp4725: support voltage reference selection

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On 30/09/16 14:19, Tomas Novotny wrote:
> MCP47x6 chip supports selection of a voltage reference (VDD, VREF buffered
> or unbuffered). MCP4725 doesn't have this feature thus the setting is
> ignored and user is warned if there is an attempt to set a value other than
> zero.
> 
> The setting is stored only in the volatile memory of the chip. You need to
> manually store it to the EEPROM of the chip via 'store_eeprom' sysfs entry.
> 
> Signed-off-by: Tomas Novotny <tomas@xxxxxxxxxx>
> ---
>  drivers/iio/dac/mcp4725.c       | 45 +++++++++++++++++++++++++++++++++++++----
>  include/linux/iio/dac/mcp4725.h |  1 +
>  2 files changed, 42 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/iio/dac/mcp4725.c b/drivers/iio/dac/mcp4725.c
> index cca935c..f8e54f1 100644
> --- a/drivers/iio/dac/mcp4725.c
> +++ b/drivers/iio/dac/mcp4725.c
> @@ -28,7 +28,9 @@
>  
>  struct mcp4725_data {
>  	struct i2c_client *client;
> +	int id;
>  	u16 vref_mv;
> +	unsigned vref_mode;
>  	u16 dac_value;
>  	bool powerdown;
>  	unsigned powerdown_mode;
> @@ -86,6 +88,7 @@ static ssize_t mcp4725_store_eeprom(struct device *dev,
>  		return 0;
>  
>  	inoutbuf[0] = 0x60; /* write EEPROM */
> +	inoutbuf[0] |= data->vref_mode << 3;
>  	inoutbuf[1] = data->dac_value >> 4;
>  	inoutbuf[2] = (data->dac_value & 0xf) << 4;
>  
> @@ -329,8 +332,10 @@ static int mcp4725_probe(struct i2c_client *client,
>  	struct mcp4725_data *data;
>  	struct iio_dev *indio_dev;
>  	struct mcp4725_platform_data *platform_data = client->dev.platform_data;
> -	u8 inbuf[3];
> +	u8 inoutbuf[3];
>  	u8 pd;
> +	u8 vref;
> +	int ret;
>  	int err;
>  
>  	if (!platform_data || !platform_data->vref_mv) {
> @@ -344,6 +349,17 @@ static int mcp4725_probe(struct i2c_client *client,
>  	data = iio_priv(indio_dev);
>  	i2c_set_clientdata(client, indio_dev);
>  	data->client = client;
> +	data->id = id->driver_data;
> +
> +	if (data->id == MCP4725 && platform_data->vref_mode > 0) {
> +		dev_warn(&client->dev, "vref mode is unavailable on MCP4725, ignoring");
> +		platform_data->vref_mode = 0;
> +	}
> +
> +	if (data->id == MCP4726 && platform_data->vref_mode > 3) {
> +		dev_err(&client->dev, "vref mode is out of range");
> +		return -EINVAL;
> +	}
>  
>  	indio_dev->dev.parent = &client->dev;
>  	indio_dev->name = id->name;
> @@ -353,17 +369,38 @@ static int mcp4725_probe(struct i2c_client *client,
>  	indio_dev->modes = INDIO_DIRECT_MODE;
>  
>  	data->vref_mv = platform_data->vref_mv;
> +	data->vref_mode = platform_data->vref_mode;
>  
>  	/* read current DAC value */
> -	err = i2c_master_recv(client, inbuf, 3);
> +	err = i2c_master_recv(client, inoutbuf, 3);
>  	if (err < 0) {
>  		dev_err(&client->dev, "failed to read DAC value");
>  		return err;
>  	}
> -	pd = (inbuf[0] >> 1) & 0x3;
> +	pd = (inoutbuf[0] >> 1) & 0x3;
>  	data->powerdown = pd > 0 ? true : false;
>  	data->powerdown_mode = pd ? pd - 1 : 2; /* largest register to gnd */
> -	data->dac_value = (inbuf[1] << 4) | (inbuf[2] >> 4);
> +	data->dac_value = (inoutbuf[1] << 4) | (inoutbuf[2] >> 4);
> +	vref = inoutbuf[0] >> 3 & 0x3;
> +
> +	if (data->id == MCP4726 && vref != data->vref_mode) {
> +		dev_info(&client->dev,
> +			"vref_mode differs (conf: %d, eeprom: %d), setting %d",
> +			data->vref_mode, vref, data->vref_mode);
> +
> +		inoutbuf[0] = 0x40;
> +		inoutbuf[0] |= data->vref_mode << 3;
> +		if (data->powerdown)
> +			inoutbuf[0] |= data->powerdown << 1;
> +		inoutbuf[1] = data->dac_value >> 4;
> +		inoutbuf[2] = (data->dac_value & 0xf) << 4;
> +
> +		ret = i2c_master_send(data->client, inoutbuf, 3);
> +		if (ret < 0)
> +			return ret;
> +		else if (ret != 3)
> +			return -EIO;
> +	}
>  
>  	return iio_device_register(indio_dev);
>  }
> diff --git a/include/linux/iio/dac/mcp4725.h b/include/linux/iio/dac/mcp4725.h
> index 91530e6..370022b 100644
> --- a/include/linux/iio/dac/mcp4725.h
> +++ b/include/linux/iio/dac/mcp4725.h
> @@ -11,6 +11,7 @@
>  
>  struct mcp4725_platform_data {
>  	u16 vref_mv;
> +	unsigned vref_mode;
Hmm. Should probably move the platform support over to using regulators.
This is a horible bit of legacy code.

Jonathan
>  };
>  
>  #endif /* IIO_DAC_MCP4725_H_ */
> 

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