Re: [PATCH 2/2] iio: adc: Add driver for the TI ADS8344 A/DC chips

Gregory CLEMENT
2019-03-22T10:13:35Z

Hi Jonathan,

On sam., mars 16 2019, Jonathan Cameron <jic23@kernel.org> wrote:

> On Fri, 15 Mar 2019 16:11:51 +0100
> Gregory CLEMENT <gregory.clement@bootlin.com> wrote:
>
>> This adds support for the Texas Instruments ADS8344 ADC chip. This chip
>> has a 16-bit 8-Channel ADC and is access directly through SPI.
>>
>> Signed-off-by: Gregory CLEMENT <gregory.clement@bootlin.com>
>
> Hi Gregory,
>
> A few minor bits and pieces inline. Some of them due I would guess to
> cut and paste from a driver where things were slightly different!

Exactly! :)

>
> If we were late in the cycle this lot would probably have been
> small enough that I'd just have reworked it whilst applying, but
> we are really early, hence you get to tidy them up ;)

No problem, I agree to have a more polished driver!

>
> Thanks,
>
> Jonathan
>
>> ---
>> drivers/iio/adc/Kconfig | 10 ++
>> drivers/iio/adc/Makefile | 1 +
>> drivers/iio/adc/ti-ads8344.c | 216 +++++++++++++++++++++++++++++++++++
>> 3 files changed, 227 insertions(+)
>> create mode 100644 drivers/iio/adc/ti-ads8344.c
>>
>> diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
>> index 76db6e5cc296..447d3a871746 100644
>> --- a/drivers/iio/adc/Kconfig
>> +++ b/drivers/iio/adc/Kconfig
>> @@ -967,6 +967,16 @@ config TI_ADS7950
>> To compile this driver as a module, choose M here: the
>> module will be called ti-ads7950.
>>
>> +config TI_ADS8344
>> + tristate "Texas Instruments ADS8344"
>> + depends on SPI && OF
>> + help
>> + If you say yes here you get support for Texas Instruments ADS8344
>> + ADC chips
>> +
>> + This driver can also be built as a module. If so, the module will be
>> + called ti-ads8344.
>> +
>> config TI_ADS8688
>> tristate "Texas Instruments ADS8688"
>> depends on SPI && OF
>> diff --git a/drivers/iio/adc/Makefile b/drivers/iio/adc/Makefile
>> index 6fcebd167524..1f3ae934111d 100644
>> --- a/drivers/iio/adc/Makefile
>> +++ b/drivers/iio/adc/Makefile
>> @@ -87,6 +87,7 @@ obj-$(CONFIG_TI_ADC128S052) += ti-adc128s052.o
>> obj-$(CONFIG_TI_ADC161S626) += ti-adc161s626.o
>> obj-$(CONFIG_TI_ADS1015) += ti-ads1015.o
>> obj-$(CONFIG_TI_ADS7950) += ti-ads7950.o
>> +obj-$(CONFIG_TI_ADS8344) += ti-ads8344.o
>> obj-$(CONFIG_TI_ADS8688) += ti-ads8688.o
>> obj-$(CONFIG_TI_ADS124S08) += ti-ads124s08.o
>> obj-$(CONFIG_TI_AM335X_ADC) += ti_am335x_adc.o
>> diff --git a/drivers/iio/adc/ti-ads8344.c b/drivers/iio/adc/ti-ads8344.c
>> new file mode 100644
>> index 000000000000..6159d8518871
>> --- /dev/null
>> +++ b/drivers/iio/adc/ti-ads8344.c
>> @@ -0,0 +1,216 @@
>> +// SPDX-License-Identifier: GPL-2.0+
>> +/*
>> + * ADS8344 16-bit 8-Channel ADC driver
>> + *
>> + * Author: Gregory CLEMENT <gregory.clement@bootlin.com>
>> + *
>> + * Datasheet: http://www.ti.com/lit/ds/symlink/ads8344.pdf
>> + */
>> +
>> +#include <linux/delay.h>
>> +#include <linux/iio/buffer.h>
>> +#include <linux/iio/iio.h>
>> +#include <linux/module.h>
>> +#include <linux/regulator/consumer.h>
>> +#include <linux/spi/spi.h>
>> +
>> +struct ads8344 {
>> + struct spi_device *spi;
>> + struct regulator *reg;
>> + struct mutex lock;
>> +
>> + u8 tx_buf ____cacheline_aligned;
>> + u16 rx_buf;
>> +};
>> +
>> +#define ADS8344_VOLTAGE_CHANNEL(chan, si) \
>> + { \
>> + .type = IIO_VOLTAGE, \
>> + .indexed = 1, \
>> + .channel = chan, \
>> + .info_mask_separate = BIT(IIO_CHAN_INFO_RAW), \
>> + .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE), \
>> + .scan_index = si, \
>> + .scan_type = { \
>
> You aren't currently providing a buffer, so please drop scan_index and
> scan_type until you are. The code won't do anything with them at the
> moment.

OK

>
>> + .sign = 'u', \
>> + .realbits = 16, \
>> + .storagebits = 16, \
>> + }, \
>> + }
>> +
>> +#define ADS8344_VOLTAGE_CHANNEL_DIFF(chan1, chan2, si) \
>> + { \
>> + .type = IIO_VOLTAGE, \
>> + .indexed = 1, \
>> + .channel = (chan1), \
>> + .channel2 = (chan2), \
>> + .differential = 1, \
>> + .info_mask_separate = BIT(IIO_CHAN_INFO_RAW), \
>> + .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE), \
>> + .scan_index = si, \
>> + .scan_type = { \
>> + .sign = 'u', \
>> + .realbits = 16, \
>> + .storagebits = 16, \
>> + }, \
>> + }
>> +
>> +static const struct iio_chan_spec ads8344_channels[] = {
>> + ADS8344_VOLTAGE_CHANNEL(0, 0),
>> + ADS8344_VOLTAGE_CHANNEL(1, 4),
>> + ADS8344_VOLTAGE_CHANNEL(2, 1),
>> + ADS8344_VOLTAGE_CHANNEL(3, 5),
>> + ADS8344_VOLTAGE_CHANNEL(4, 2),
>> + ADS8344_VOLTAGE_CHANNEL(5, 6),
>> + ADS8344_VOLTAGE_CHANNEL(6, 3),
>> + ADS8344_VOLTAGE_CHANNEL(7, 7),
>> + ADS8344_VOLTAGE_CHANNEL_DIFF(0, 1, 8),
>> + ADS8344_VOLTAGE_CHANNEL_DIFF(2, 3, 9),
>> + ADS8344_VOLTAGE_CHANNEL_DIFF(4, 5, 10),
>> + ADS8344_VOLTAGE_CHANNEL_DIFF(6, 7, 11),
>> + ADS8344_VOLTAGE_CHANNEL_DIFF(1, 0, 12),
>> + ADS8344_VOLTAGE_CHANNEL_DIFF(3, 2, 13),
>> + ADS8344_VOLTAGE_CHANNEL_DIFF(5, 4, 14),
>> + ADS8344_VOLTAGE_CHANNEL_DIFF(7, 6, 15),
>> +};
>> +
>> +static int ads8344_adc_conversion(struct ads8344 *adc, int channel,
>> + bool differential)
>> +{
>> + struct spi_device *spi = adc->spi;
>> + int ret;
>> +
>> + /* start bit */
>> + adc->tx_buf = BIT(7);
>> + /* single-ended or differential */
>> + adc->tx_buf |= differential ? 0 : BIT(2);
>> + /* select channel(s) */
> The moment you need comments to say what a bit is, you are
> almost always better off adding some defines so that this
> block becomes something like.
>
>
> adc->tx_buff = ADS8344_START;
> if (!differential)
> adc->tx_buff |= ADS8344_SINGLE_END;
> adc->tx_buff |= ADS8344_CHANNEL(channel);
> adc->tx_buff |= ADS8344_CLOCK_INTERNAL;
>
> Then you can drop the comments and the defines are nice
> and easy to check against a datasheet as they are all in
> one place.

OK, I agree it looks better.

>
>> + adc->tx_buf |= channel << 4;
>> + /* internal clock mode */
>> + adc->tx_buf |= 0x2;
>> +
>> + ret = spi_write(spi, &adc->tx_buf, 1);
>> + if (ret)
>> + return ret;
>> +
>> + udelay(9);
>> +
>> + ret = spi_read(spi, &adc->rx_buf, 2);
>> + if (ret)
>> + return ret;
>> +
>> + return adc->rx_buf;
>> +}
>> +
>> +static int ads8344_read_raw(struct iio_dev *iio,
>> + struct iio_chan_spec const *channel, int *value,
>> + int *shift, long mask)
>> +{
>> + struct ads8344 *adc = iio_priv(iio);
>> +
>> + switch (mask) {
>> + case IIO_CHAN_INFO_RAW:
>> + mutex_lock(&adc->lock);
>> + *value = ads8344_adc_conversion(adc, channel->scan_index,
>> + channel->differential);
>> + mutex_unlock(&adc->lock);
>> + if (*value < 0)
>> + return *value;
>> +
>> + return IIO_VAL_INT;
>> + case IIO_CHAN_INFO_SCALE:
>> + *value = regulator_get_voltage(adc->reg);
>> + if (*value < 0)
>> + return *value;
>> +
>> + /* convert regulator output voltage to mV */
>> + *value /= 1000;
>> + *shift = 16;
>> +
>> + return IIO_VAL_FRACTIONAL_LOG2;
>> + default:
>> + return -EINVAL;
>> + }
>> +}
>> +
>> +static const struct iio_info ads8344_info = {
>> + .read_raw = ads8344_read_raw,
>> +};
>> +
>> +static int ads8344_probe(struct spi_device *spi)
>> +{
>> + struct iio_dev *indio_dev;
>> + struct ads8344 *adc;
>> + int ret;
>> +
>> + indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*adc));
>> + if (!indio_dev)
>> + return -ENOMEM;
>> +
>> + adc = iio_priv(indio_dev);
>> + adc->spi = spi;
>> + mutex_init(&adc->lock);
>> +
>> + indio_dev->name = dev_name(&spi->dev);
>> + indio_dev->dev.parent = &spi->dev;
>> + indio_dev->dev.of_node = spi->dev.of_node;
>> + indio_dev->info = &ads8344_info;
>> + indio_dev->modes = INDIO_DIRECT_MODE;
>> + indio_dev->channels = ads8344_channels;
>> + indio_dev->num_channels = ARRAY_SIZE(ads8344_channels);
>> +
>> + adc->reg = devm_regulator_get(&spi->dev, "vref");
>> + if (IS_ERR(adc->reg))
>> + return PTR_ERR(adc->reg);
>> +
>> + ret = regulator_enable(adc->reg);
>> + if (ret)
>> + return ret;
>> +
>> + spi_set_drvdata(spi, indio_dev);
>> +
>> + ret = iio_device_register(indio_dev);
>> + if (ret)
>> + goto err_buffer_cleanup;
>> +
>> + return 0;
>> +err_buffer_cleanup:
>
> That is not a useful or correct label.. Give it a better name!

Actually I am going to remove the goto.

>
>> + regulator_disable(adc->reg);
>> +
>> + return ret;
>> +}
>> +
>> +static int ads8344_remove(struct spi_device *spi)
>> +{
>> + struct iio_dev *indio_dev = spi_get_drvdata(spi);
>> + struct ads8344 *adc = iio_priv(indio_dev);
>> +
>> + iio_device_unregister(indio_dev);
>> + regulator_disable(adc->reg);
>> +
>> + return 0;
>> +}
>> +
>> +#ifdef CONFIG_OF
>
> Given there isn't currently any other way of (normally
> at least) instantiating this I wouldn't bother with the config guards.

Right and we already have a depend on OF in the Kconfig

> Also see below for additional comment on this.
>
>> +
>> +static const struct of_device_id ads8344_dt_ids[] = {
>> + { .compatible = "ti,ads8344", },
>> + {}
>> +};
>> +MODULE_DEVICE_TABLE(of, ads8344_dt_ids);
>> +
>> +#endif
>> +
>> +static struct spi_driver ads8344_driver = {
>> + .driver = {
>> + .name = "ads8344",
>> + .of_match_table = of_match_ptr(ads8344_dt_ids),
>
> Don't use of_match_ptr as it breaks the magic ACPI binding which
> uses the DT tables.
OK

Thanks,

Gregory

>
>> + },
>> + .probe = ads8344_probe,
>> + .remove = ads8344_remove,
>> +};
>> +module_spi_driver(ads8344_driver);
>> +
>> +MODULE_AUTHOR("Gregory CLEMENT <gregory.clement@bootlin.com>");
>> +MODULE_DESCRIPTION("ADS8344 driver");
>> +MODULE_LICENSE("GPL v2");
>
>
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--
Gregory Clement, Bootlin
Embedded Linux and Kernel engineering