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Date: Sun, 18 Sep 2022 15:30:21 +0100
From: Jonathan Cameron <jic23@...nel.org>
To: Ciprian Regus <ciprian.regus@...log.com>
Cc: <linux-iio@...r.kernel.org>, <devicetree@...r.kernel.org>,
<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 4/5] drivers: iio: adc: LTC2499 support
On Fri, 16 Sep 2022 17:09:21 +0300
Ciprian Regus <ciprian.regus@...log.com> wrote:
> The LTC2499 is a 16-channel (eight differential), 24-bit,
> ADC with Easy Drive technology and a 2-wire, I2C interface.
>
> Implement support for the LTC2499 ADC by extending the LTC2497
> driver. A new chip_info struct is added to differentiate between
> chip types and resolutions when reading data from the device.
>
> Datasheet: https://www.analog.com/media/en/technical-documentation/data-sheets/2499fe.pdf
> Signed-off-by: Ciprian Regus <ciprian.regus@...log.com>
I'm not certain why (as I have the prerequisit on the tree) but this
didn't apply cleanly. Please give the result of my manual intervention a
quick sanity check.
Thanks,
Jonathan
> ---
> changes in v3:
> - set the correct chip info indexes for i2c_device_id entries.
> - added the asm/unaligned.h header.
> - removed TYPE_LTC2496.
> - moved the ltc2497_chip_type enum to ltc2497.c file.
> - removed the name setting.
> drivers/iio/adc/ltc2496.c | 8 ++++-
> drivers/iio/adc/ltc2497-core.c | 2 +-
> drivers/iio/adc/ltc2497.c | 61 +++++++++++++++++++++++++++++++---
> drivers/iio/adc/ltc2497.h | 5 +++
> 4 files changed, 69 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/iio/adc/ltc2496.c b/drivers/iio/adc/ltc2496.c
> index dfb3bb5997e5..bf89d5ae19af 100644
> --- a/drivers/iio/adc/ltc2496.c
> +++ b/drivers/iio/adc/ltc2496.c
> @@ -15,6 +15,7 @@
> #include <linux/iio/driver.h>
> #include <linux/module.h>
> #include <linux/mod_devicetable.h>
> +#include <linux/property.h>
>
> #include "ltc2497.h"
>
> @@ -74,6 +75,7 @@ static int ltc2496_probe(struct spi_device *spi)
> spi_set_drvdata(spi, indio_dev);
> st->spi = spi;
> st->common_ddata.result_and_measure = ltc2496_result_and_measure;
> + st->common_ddata.chip_info = device_get_match_data(dev);
>
> return ltc2497core_probe(dev, indio_dev);
> }
> @@ -85,8 +87,12 @@ static void ltc2496_remove(struct spi_device *spi)
> ltc2497core_remove(indio_dev);
> }
>
> +static const struct ltc2497_chip_info ltc2496_info = {
> + .resolution = 16,
> +};
> +
> static const struct of_device_id ltc2496_of_match[] = {
> - { .compatible = "lltc,ltc2496", },
> + { .compatible = "lltc,ltc2496", .data = <c2496_info, },
> {},
> };
> MODULE_DEVICE_TABLE(of, ltc2496_of_match);
> diff --git a/drivers/iio/adc/ltc2497-core.c b/drivers/iio/adc/ltc2497-core.c
> index 2a485c8a1940..b2752399402c 100644
> --- a/drivers/iio/adc/ltc2497-core.c
> +++ b/drivers/iio/adc/ltc2497-core.c
> @@ -95,7 +95,7 @@ static int ltc2497core_read_raw(struct iio_dev *indio_dev,
> return ret;
>
> *val = ret / 1000;
> - *val2 = 17;
> + *val2 = ddata->chip_info->resolution + 1;
>
> return IIO_VAL_FRACTIONAL_LOG2;
>
> diff --git a/drivers/iio/adc/ltc2497.c b/drivers/iio/adc/ltc2497.c
> index f7c786f37ceb..36248423a7a6 100644
> --- a/drivers/iio/adc/ltc2497.c
> +++ b/drivers/iio/adc/ltc2497.c
> @@ -12,18 +12,31 @@
> #include <linux/iio/driver.h>
> #include <linux/module.h>
> #include <linux/mod_devicetable.h>
> +#include <linux/property.h>
> +
> +#include <asm/unaligned.h>
>
> #include "ltc2497.h"
>
> +enum ltc2497_chip_type {
> + TYPE_LTC2497,
> + TYPE_LTC2499,
> +};
> +
> struct ltc2497_driverdata {
> /* this must be the first member */
> struct ltc2497core_driverdata common_ddata;
> struct i2c_client *client;
> + u32 recv_size;
> + u32 sub_lsb;
> /*
> * DMA (thus cache coherency maintenance) may require the
> * transfer buffers to live in their own cache lines.
> */
> - __be32 buf __aligned(IIO_DMA_MINALIGN);
> + union {
> + __be32 d32;
> + u8 d8[3];
> + } data __aligned(IIO_DMA_MINALIGN);
> };
>
> static int ltc2497_result_and_measure(struct ltc2497core_driverdata *ddata,
> @@ -34,13 +47,29 @@ static int ltc2497_result_and_measure(struct ltc2497core_driverdata *ddata,
> int ret;
>
> if (val) {
> - ret = i2c_master_recv(st->client, (char *)&st->buf, 3);
> + if (st->recv_size == 3)
> + ret = i2c_master_recv(st->client, (char *)&st->data.d8, st->recv_size);
> + else
> + ret = i2c_master_recv(st->client, (char *)&st->data.d32, st->recv_size);
> +
> if (ret < 0) {
> dev_err(&st->client->dev, "i2c_master_recv failed\n");
> return ret;
> }
>
> - *val = (be32_to_cpu(st->buf) >> 14) - (1 << 17);
> + /*
> + * The data format is 16/24 bit 2s complement, but with an upper sign bit on the
> + * resolution + 1 position, which is set for positive values only. Given this
> + * bit's value, subtracting BIT(resolution + 1) from the ADC's result is
> + * equivalent to a sign extension.
> + */
> + if (st->recv_size == 3) {
> + *val = (get_unaligned_be24(st->data.d8) >> st->sub_lsb)
> + - BIT(ddata->chip_info->resolution + 1);
> + } else {
> + *val = (be32_to_cpu(st->data.d32) >> st->sub_lsb)
> + - BIT(ddata->chip_info->resolution + 1);
> + }
> }
>
> ret = i2c_smbus_write_byte(st->client,
> @@ -54,9 +83,11 @@ static int ltc2497_result_and_measure(struct ltc2497core_driverdata *ddata,
> static int ltc2497_probe(struct i2c_client *client,
> const struct i2c_device_id *id)
> {
> + const struct ltc2497_chip_info *chip_info;
> struct iio_dev *indio_dev;
> struct ltc2497_driverdata *st;
> struct device *dev = &client->dev;
> + u32 resolution;
>
> if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C |
> I2C_FUNC_SMBUS_WRITE_BYTE))
> @@ -71,6 +102,15 @@ static int ltc2497_probe(struct i2c_client *client,
> st->client = client;
> st->common_ddata.result_and_measure = ltc2497_result_and_measure;
>
> + chip_info = device_get_match_data(dev);
> + if (!chip_info)
> + chip_info = (const struct ltc2497_chip_info *)id->driver_data;
> + st->common_ddata.chip_info = chip_info;
> +
> + resolution = chip_info->resolution;
> + st->sub_lsb = 31 - (resolution + 1);
> + st->recv_size = BITS_TO_BYTES(resolution) + 1;
> +
> return ltc2497core_probe(dev, indio_dev);
> }
>
> @@ -83,14 +123,25 @@ static int ltc2497_remove(struct i2c_client *client)
> return 0;
> }
>
> +static const struct ltc2497_chip_info ltc2497_info[] = {
> + [TYPE_LTC2497] = {
> + .resolution = 16,
> + },
> + [TYPE_LTC2499] = {
> + .resolution = 24,
> + },
> +};
> +
> static const struct i2c_device_id ltc2497_id[] = {
> - { "ltc2497", 0 },
> + { "ltc2497", (kernel_ulong_t)<c2497_info[TYPE_LTC2497] },
> + { "ltc2499", (kernel_ulong_t)<c2497_info[TYPE_LTC2499] },
> { }
> };
> MODULE_DEVICE_TABLE(i2c, ltc2497_id);
>
> static const struct of_device_id ltc2497_of_match[] = {
> - { .compatible = "lltc,ltc2497", },
> + { .compatible = "lltc,ltc2497", .data = <c2497_info[TYPE_LTC2497] },
> + { .compatible = "lltc,ltc2499", .data = <c2497_info[TYPE_LTC2499] },
> {},
> };
> MODULE_DEVICE_TABLE(of, ltc2497_of_match);
> diff --git a/drivers/iio/adc/ltc2497.h b/drivers/iio/adc/ltc2497.h
> index d0b42dd6b8ad..71957fc7e1ba 100644
> --- a/drivers/iio/adc/ltc2497.h
> +++ b/drivers/iio/adc/ltc2497.h
> @@ -4,9 +4,14 @@
> #define LTC2497_CONFIG_DEFAULT LTC2497_ENABLE
> #define LTC2497_CONVERSION_TIME_MS 150ULL
>
> +struct ltc2497_chip_info {
> + u32 resolution;
> +};
> +
> struct ltc2497core_driverdata {
> struct regulator *ref;
> ktime_t time_prev;
> + const struct ltc2497_chip_info *chip_info;
> u8 addr_prev;
> int (*result_and_measure)(struct ltc2497core_driverdata *ddata,
> u8 address, int *val);
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