Re: [PATCH 3/3] iio: adc: new driver to support Linear technology's ltc2496

["Ardelean, Alexandru" <alexandru.Ardelean@analog.com>]

On Mon, 2019-11-11 at 22:40 +0100, Uwe Kleine-König wrote:
> This chip is similar to the LTC2497 ADC, it just uses SPI instead of I2C
> and so has a slightly different protocol. The channel definitions are
> shared between the two drivers.

Much of this code is duplicated from the i2c/base ltc2497.o driver.

I would leave most of this code in the base/common driver and export the
i2c/spi read hooks.

You can check [as an example] the ad7606 driver.

That one passes some  bus_ops  struct from the SPI & Parallel drivers to
the common probe.

I agree that regmap isn't usable here, but a bus_ops struct [that is
defined in ltc2497.h] should be doable.

Thanks
Alex

> 
> Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
> ---
>  drivers/iio/adc/Kconfig   |  10 ++
>  drivers/iio/adc/Makefile  |   1 +
>  drivers/iio/adc/ltc2496.c | 208 ++++++++++++++++++++++++++++++++++++++
>  3 files changed, 219 insertions(+)
>  create mode 100644 drivers/iio/adc/ltc2496.c
> 
> diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
> index f0af3a42f53c..deb86f6039b3 100644
> --- a/drivers/iio/adc/Kconfig
> +++ b/drivers/iio/adc/Kconfig
> @@ -492,6 +492,16 @@ config LTC2485
>  	  To compile this driver as a module, choose M here: the module
> will be
>  	  called ltc2485.
>  
> +config LTC2496
> +	tristate "Linear Technology LTC2496 ADC driver"
> +	depends on SPI

Regarding [patch2-note1], this Kconfig symbols would be LTC2497_SPI

> +	help
> +	  Say yes here to build support for Linear Technology LTC2496
> +	  16-Bit 8-/16-Channel Delta Sigma ADC.
> +
> +	  To compile this driver as a module, choose M here: the module
> will be
> +	  called ltc2496.
> +
>  config LTC2497

Regarding [patch2-note1], this Kconfig symbols would become LTC2497_I2C.
And a new config LTC2497 could be added, but without any title, so that it
cannot be selected in menuconfig.

>  	tristate "Linear Technology LTC2497 ADC driver"
>  	depends on I2C
> diff --git a/drivers/iio/adc/Makefile b/drivers/iio/adc/Makefile
> index 660242c2cca7..afe2b6db4a5e 100644
> --- a/drivers/iio/adc/Makefile
> +++ b/drivers/iio/adc/Makefile
> @@ -47,6 +47,7 @@ obj-$(CONFIG_LPC18XX_ADC) += lpc18xx_adc.o
>  obj-$(CONFIG_LPC32XX_ADC) += lpc32xx_adc.o
>  obj-$(CONFIG_LTC2471) += ltc2471.o
>  obj-$(CONFIG_LTC2485) += ltc2485.o
> +obj-$(CONFIG_LTC2496) += ltc2496.o ltc249x.o
>  obj-$(CONFIG_LTC2497) += ltc2497.o ltc249x.o
>  obj-$(CONFIG_MAX1027) += max1027.o
>  obj-$(CONFIG_MAX11100) += max11100.o
> diff --git a/drivers/iio/adc/ltc2496.c b/drivers/iio/adc/ltc2496.c
> new file mode 100644
> index 000000000000..0b0a7aa8987f
> --- /dev/null
> +++ b/drivers/iio/adc/ltc2496.c
> @@ -0,0 +1,208 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * ltc2496.c - Driver for Analog Devices/Linear Technology LTC2496 ADC
> + *
> + * Based on ltc2497.c which has
> + * Copyright (C) 2017 Analog Devices Inc.
> + *
> + * Licensed under the GPL-2.
> + *
> + * Datasheet: 
> https://www.analog.com/media/en/technical-documentation/data-sheets/2496fc.pdf
> + */
> +
> +#include <linux/delay.h>
> +#include <linux/spi/spi.h>
> +#include <linux/iio/iio.h>
> +#include <linux/iio/driver.h>
> +#include <linux/iio/sysfs.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/regulator/consumer.h>
> +
> +#include "ltc249x.h"
> +
> +struct ltc2496_st {
> +	struct spi_device *spi;
> +	struct regulator *ref;
> +	ktime_t	time_prev;
> +	u8 addr_prev;
> +};
> +
> +static int ltc2496_wait_conv(struct ltc2496_st *st)
> +{
> +	s64 time_elapsed;
> +
> +	time_elapsed = ktime_ms_delta(ktime_get(), st->time_prev);
> +
> +	if (time_elapsed < LTC249X_CONVERSION_TIME_MS) {
> +		/* delay if conversion time not passed
> +		 * since last read or write
> +		 */
> +		if (msleep_interruptible(
> +		    LTC249X_CONVERSION_TIME_MS - time_elapsed))
> +			return -ERESTARTSYS;
> +
> +		return 0;
> +	}
> +
> +	if (time_elapsed - LTC249X_CONVERSION_TIME_MS <= 0) {
> +		/* We're in automatic mode -
> +		 * so the last reading is still not outdated
> +		 */
> +		return 0;
> +	}
> +
> +	return 1;
> +}
> +
> +static int ltc2496_read(struct ltc2496_st *st, u8 address, int *val)
> +{
> +	struct spi_device *spi = st->spi;
> +	int ret;
> +	unsigned char txbuf[3] = { LTC249X_ENABLE | address, };
> +	unsigned char rxbuf[3];
> +	struct spi_transfer t = {
> +		.tx_buf = txbuf,
> +		.rx_buf = rxbuf,
> +		.len = sizeof(txbuf),
> +	};
> +
> +	ret = ltc2496_wait_conv(st);
> +	if (ret < 0)
> +		return ret;
> +
> +	if (ret || st->addr_prev != address) {
> +		ret = spi_sync_transfer(spi, &t, 1);
> +		if (ret < 0)
> +			return ret;
> +		st->addr_prev = address;
> +		if (msleep_interruptible(LTC249X_CONVERSION_TIME_MS))
> +			return -ERESTARTSYS;
> +	}
> +
> +	ret = spi_sync_transfer(spi, &t, 1);
> +	if (ret < 0)  {
> +		dev_err(&spi->dev, "spi_sync_transfer failed\n");
> +		return ret;
> +	}
> +	st->time_prev = ktime_get();
> +
> +	/* convert and shift the result,
> +	 * and finally convert from offset binary to signed integer
> +	 */
> +	*val = ((rxbuf[0] & 0x3f) << 12 | rxbuf[1] << 4 | rxbuf[2] >> 4)
> +		- (1 << 17);
> +
> +	return ret;
> +}
> +			    int *val, int *val2, long mask)
> +{
> +	struct ltc2496_st *st = iio_priv(indio_dev);
> +	int ret;
> +
> +	switch (mask) {
> +	case IIO_CHAN_INFO_RAW:
> +		mutex_lock(&indio_dev->mlock);
> +		ret = ltc2496_read(st, chan->address, val);
> +		mutex_unlock(&indio_dev->mlock);
> +		if (ret < 0)
> +			return ret;
> +
> +		return IIO_VAL_INT;
> +
> +	case IIO_CHAN_INFO_SCALE:
> +		ret = regulator_get_voltage(st->ref);
> +		if (ret < 0)
> +			return ret;
> +
> +		*val = ret / 1000;
> +		*val2 = 17;
> +
> +		return IIO_VAL_FRACTIONAL_LOG2;
> +
> +	default:
> +		return -EINVAL;
> +	}
> +}
> +
> +static const struct iio_info ltc2496_info = {
> +	.read_raw = ltc2496_read_raw,
> +};
> +
> +static int ltc2496_probe(struct spi_device *spi)
> +{
> +	struct iio_dev *indio_dev;
> +	struct ltc2496_st *st;
> +	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 = "ltc2496";
> +	indio_dev->info = &ltc2496_info;
> +	indio_dev->modes = INDIO_DIRECT_MODE;
> +	indio_dev->channels = ltc249x_channel;
> +	indio_dev->num_channels = ltc249x_num_channels;
> +
> +	st->ref = devm_regulator_get(&spi->dev, "vref");
> +	if (IS_ERR(st->ref))
> +		return PTR_ERR(st->ref);
> +
> +	ret = regulator_enable(st->ref);
> +	if (ret < 0)
> +		return ret;
> +
> +	st->addr_prev = 0;
> +	st->time_prev = ktime_get();
> +
> +	ret = iio_device_register(indio_dev);
> +	if (ret < 0)
> +		goto err_regulator_disable;
> +
> +	return 0;
> +
> +err_regulator_disable:
> +	regulator_disable(st->ref);
> +
> +	return ret;
> +}
> +
> +static int ltc2496_remove(struct spi_device *spi)
> +{
> +	struct iio_dev *indio_dev = spi_get_drvdata(spi);
> +	struct ltc2496_st *st = iio_priv(indio_dev);
> +
> +	iio_device_unregister(indio_dev);
> +	regulator_disable(st->ref);
> +
> +	return 0;
> +}
> +
> +static const struct of_device_id ltc2496_of_match[] = {
> +	{ .compatible = "lltc,ltc2496", },
> +	{},
> +};
> +MODULE_DEVICE_TABLE(of, ltc2496_of_match);
> +
> +static struct spi_driver ltc2496_driver = {
> +	.driver = {
> +		.name = "ltc2496",
> +		.of_match_table = of_match_ptr(ltc2496_of_match),
> +	},
> +	.probe = ltc2496_probe,
> +	.remove = ltc2496_remove,
> +};
> +module_spi_driver(ltc2496_driver);
> +
> +MODULE_AUTHOR("Uwe Kleine-König <u.kleine-könig@pengutronix.de>");
> +MODULE_DESCRIPTION("Linear Technology LTC2496 ADC driver");
> +MODULE_LICENSE("GPL v2");