Re: [PATCH v4 2/2] iio: add MCP4728 I2C DAC driver

[Andrea Collamati]

Hi Jonathan,

I tested the driver and I didn't find any issue.

These are the tests I performed:

Test Configuration:
SW:
git://git.kernel.org/pub/scm/linux/kernel/git/jic23/iio.git
commit: ee812337ee74cc403b4fbd85840dbe1b21d9a60f

HW:
- Aster board from Toradex hosting imx7d processor
- Adafruit MCP4728 https://www.adafruit.com/product/4470

TEST:

Probe Test                                OK
#> insmod mcp4728.ko

Read Scales                                OK
~# cat /sys/devices/platform/soc/30800000.bus/30a50000.i2c/i2c-3/3-0064/iio:device1/out_voltage_scale_available
0.805664 0.500000 1.000000

Write DAC CH0                            OK
#>iio_attr -c mcp4728 voltage0 scale    1.000000
#>iio_attr -c mcp4728 voltage0 raw         750
Voltage Monitor Reading:                749 mV

Write DAC CH1                            OK
#>iio_attr -c mcp4728 voltage1 scale    0.5
#>iio_attr -c mcp4728 voltage1 raw        750
Voltage Monitor Reading:                378 mV

Write DAC CH2                            OK
#>iio_attr -c mcp4728 voltage2 scale    0.805664
#>iio_attr -c mcp4728 voltage2 raw        750
Voltage Monitor Reading:                603 mV ~ 750*0.805664 ~ 604 mV

Write DAC CH3                            OK
#>iio_attr -c mcp4728 voltage3 scale    1.000000
#>iio_attr -c mcp4728 voltage3 raw        350
Voltage Monitor Reading:                354 mV

Store EEPROM                            OK
#>echo y > /sys/devices/platform/soc/30800000.bus/30a50000.i2c/i2c-3/3-0064/iio:device1/store_eeprom
#>power cycle board
Voltage Monitor Reading CH0                749 mV
Voltage Monitor Reading CH1                378 mV
Voltage Monitor Reading CH2                605 mV
Voltage Monitor Reading CH3                355 mV

Power Down CH0
#>iio_attr -c mcp4728 voltage0 powerdown_mode 1kohm_to_gnd
#>iio_attr -c mcp4728 voltage0 powerdown 1
Voltage Monitor Reading CH0                 0 mV

Power Down CH1
#>iio_attr -c mcp4728 voltage1 powerdown_mode 1kohm_to_gnd
#>iio_attr -c mcp4728 voltage1 powerdown 1
Voltage Monitor Reading CH1                 0 mV

Power Down CH2
#>iio_attr -c mcp4728 voltage2 powerdown_mode 1kohm_to_gnd
#>iio_attr -c mcp4728 voltage2 powerdown 1
Voltage Monitor Reading CH2                 0 mV

Power Down CH3
#>iio_attr -c mcp4728 voltage3 powerdown_mode 1kohm_to_gnd
#>iio_attr -c mcp4728 voltage3 powerdown 1
Voltage Monitor Reading CH3                 0 mV


Regards

        Andrea

On 8/5/23 20:28, Jonathan Cameron wrote:
> On Thu,  3 Aug 2023 14:56:35 +0200
> Andrea Collamati <andrea.collamati@xxxxxxxxx> wrote:
>
>> MCP4728 is a 12-bit quad channel DAC with I2C interface.
>>
>> support for:
>>  * per-channel gain
>>  * per-channel power state
>>  * per-channel power down mode control
>>  * per-channel vref selection internal/vdd
>>  * store current state to on-chip EEPROM
>>
>> Signed-off-by: Andrea Collamati <andrea.collamati@xxxxxxxxx>
> Hi Andrea,
>
> On this final read through I noticed a few minor things. Rather than
> get you to do a v5 I've made the changes whilst applying. Please
> take a sanity check at
> https://git.kernel.org/pub/scm/linux/kernel/git/jic23/iio.git/log/?h=testing
> to make sure I didn't break anything and let me know if I did!
>
> Applied with the below mentioned changes to the togreg branch of iio.git
> which is initially pushed out as testing to let 0-day poke at it and see
> if it can find any problems.
>
> Thanks,
>
> Jonathan
>
>> diff --git a/drivers/iio/dac/mcp4728.c b/drivers/iio/dac/mcp4728.c
>> new file mode 100644
>> index 000000000000..ba3eab349b0a
>> --- /dev/null
>> +++ b/drivers/iio/dac/mcp4728.c
>> @@ -0,0 +1,626 @@
> ...
>
>
>
>> +
>> +static int mcp4728_set_scale(int channel, struct mcp4728_data *data, int val,
>> +			     int val2)
>> +{
>> +	int scale = mcp4728_find_matching_scale(data, val, val2);
>> +
>> +	if (scale < 0)
>> +		return scale;
>> +
>> +	switch (scale) {
>> +	case MCP4728_SCALE_VDD:
>> +		data->chdata[channel].ref_mode = MCP4728_VREF_EXTERNAL_VDD;
>> +		break;
>> +	case MCP4728_SCALE_VINT_NO_GAIN:
>> +		data->chdata[channel].ref_mode = MCP4728_VREF_INTERNAL_2048mV;
>> +		data->chdata[channel].g_mode   = MCP4728_GAIN_X1;
>> +		break;
>> +	case MCP4728_SCALE_VINT_GAIN_X2:
>> +		data->chdata[channel].ref_mode = MCP4728_VREF_INTERNAL_2048mV;
>> +		data->chdata[channel].g_mode   = MCP4728_GAIN_X2;
>> +		break;
>> +	default:
>> +		return -EINVAL;
>> +	}
>> +	return 0;
> return instead of breaking above as nothing to be done after the switch.
> Side effect of that is this return 0 not needed.
>
>> +}
> ...
>
>> +static int mcp4728_write_raw(struct iio_dev *indio_dev,
>> +			     struct iio_chan_spec const *chan, int val,
>> +			     int val2, long mask)
>> +{
>> +	struct mcp4728_data *data = iio_priv(indio_dev);
>> +	int ret;
>> +
>> +	switch (mask) {
>> +	case IIO_CHAN_INFO_RAW:
>> +		if (val < 0 || val > GENMASK(MCP4728_RESOLUTION - 1, 0))
>> +			return -EINVAL;
>> +		data->chdata[chan->channel].dac_value = val;
>> +		ret = mcp4728_program_channel_cfg(chan->channel, indio_dev);
>> +		break;
> Direct returns preferred if no cleanup to do.
>
>> +	case IIO_CHAN_INFO_SCALE:
>> +		ret = mcp4728_set_scale(chan->channel, data, val, val2);
>> +		if (ret)
>> +			break;
>> +
>> +		ret = mcp4728_program_channel_cfg(chan->channel, indio_dev);
>> +		break;
>> +	default:
>> +		ret = -EINVAL;
>> +		break;
>> +	}
>> +
>> +	return ret;
>> +}
>
>
>> +static int mcp4728_init_channels_data(struct mcp4728_data *data)
>> +{
>> +	u8 inbuf[MCP4728_READ_RESPONSE_LEN];
>> +	int ret;
>> +	unsigned int i;
>> +
>> +	ret = i2c_master_recv(data->client, inbuf, MCP4728_READ_RESPONSE_LEN);
>> +	if (ret < 0) {
>> +		dev_err(&data->client->dev,
>> +			"failed to read mcp4728 conf. Err=%d\n", ret);
>> +		return ret;
> As this is only called from probe, we should still use dev_err_probe() in here
> as mentioned below.
>
>
>> +	} else if (ret != MCP4728_READ_RESPONSE_LEN) {
>> +		dev_err(&data->client->dev,
>> +			"failed to read mcp4728 conf. Wrong Response Len ret=%d\n",
>> +			ret);
>> +		return -EIO;
>> +	}
>> +
>> +	for (i = 0; i < MCP4728_N_CHANNELS; i++) {
>> +		struct mcp4728_channel_data *ch = &data->chdata[i];
>> +		u8 r2				= inbuf[i * 6 + 1];
>> +		u8 r3				= inbuf[i * 6 + 2];
>> +
>> +		ch->dac_value = FIELD_GET(MCP4728_DAC_H_MASK, r2) << 8 |
>> +				FIELD_GET(MCP4728_DAC_L_MASK, r3);
>> +		ch->ref_mode = FIELD_GET(MCP4728_VREF_MASK, r2);
>> +		ch->pd_mode  = FIELD_GET(MCP4728_PDMODE_MASK, r2);
>> +		ch->g_mode   = FIELD_GET(MCP4728_GAIN_MASK, r2);
>> +	}
>> +
>> +	return 0;
>> +}
> ...
>
>> +static int mcp4728_probe(struct i2c_client *client)
>> +{
>> +	const struct i2c_device_id *id = i2c_client_get_device_id(client);
>> +	struct mcp4728_data *data;
>> +	struct iio_dev *indio_dev;
>> +	int err;
>> +
>> +	indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*data));
>> +	if (!indio_dev)
>> +		return -ENOMEM;
>> +
>> +	data = iio_priv(indio_dev);
>> +	i2c_set_clientdata(client, indio_dev);
>> +	data->client = client;
>> +
>> +	data->vdd_reg = devm_regulator_get(&client->dev, "vdd");
>> +	if (IS_ERR(data->vdd_reg))
>> +		return PTR_ERR(data->vdd_reg);
>> +
>> +	err = regulator_enable(data->vdd_reg);
>> +	if (err)
>> +		return err;
>> +
>> +	err = devm_add_action_or_reset(&client->dev, mcp4728_reg_disable,
>> +				       data->vdd_reg);
>> +	if (err)
>> +		return err;
>> +
>> +	/* MCP4728 has internal EEPROM that save each channel boot configuration.
> Trivial but comment syntax in IIO (there are some differences in a few other subsystems)
> is
> 	/*
> 	 * MCP...
>
>> +	 * It means that device configuration is unknown to the driver at kernel boot.
>> +	 * mcp4728_init_channels_data reads back DAC settings and stores them in data
>> +	 * structure.
>> +	 */
>> +	err = mcp4728_init_channels_data(data);
>> +	if (err) {
> I'd missed this previously but dev_err_probe() has several advantages in that
> it handles deferring neatly and also ends up with less code.
>
>> +		dev_err(&client->dev,
>> +			"failed to read mcp4728 current configuration\n");
>> +		return err;
>> +	}
>> +
>> +	err = mcp4728_init_scales_avail(data);
>> +	if (err) {
>> +		dev_err(&client->dev, "failed to init scales\n");
>> +		return err;
>> +	}
>> +
>> +	indio_dev->name		= id->name;
>> +	indio_dev->info		= &mcp4728_info;
>> +	indio_dev->channels	= mcp4728_channels;
>> +	indio_dev->num_channels = MCP4728_N_CHANNELS;
>> +	indio_dev->modes	= INDIO_DIRECT_MODE;
>> +
>> +	return devm_iio_device_register(&client->dev, indio_dev);
>> +}