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Date: Mon, 22 Aug 2022 20:37:31 +0100
From: Jonathan Cameron <jic23@...nel.org>
To: Ciprian Regus <ciprian.regus@...log.com>
Cc: <krzysztof.kozlowski+dt@...aro.org>, <robh+dt@...nel.org>,
<linux-iio@...r.kernel.org>, <devicetree@...r.kernel.org>,
<linux-kernel@...r.kernel.org>, <u.kleine-koenig@...gutronix.de>
Subject: Re: [PATCH 2/3] drivers: iio: adc: LTC2499 support
On Mon, 22 Aug 2022 15:51:05 +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>
Hi Ciprian,
Various comments inline.
Thanks,
Jonathan
> ---
> drivers/iio/adc/ltc2496.c | 8 +++++++-
> drivers/iio/adc/ltc2497-core.c | 2 +-
> drivers/iio/adc/ltc2497.c | 34 +++++++++++++++++++++++++++++-----
> drivers/iio/adc/ltc2497.h | 13 ++++++++++++-
> 4 files changed, 49 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/iio/adc/ltc2496.c b/drivers/iio/adc/ltc2496.c
> index dfb3bb5997e5..98338104c24a 100644
> --- a/drivers/iio/adc/ltc2496.c
> +++ b/drivers/iio/adc/ltc2496.c
> @@ -14,6 +14,7 @@
> #include <linux/iio/iio.h>
> #include <linux/iio/driver.h>
> #include <linux/module.h>
> +#include <linux/property.h>
why?
> #include <linux/mod_devicetable.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 struct chip_info ltc2496_info = {
> + .resolution = 16,
> +};
> +
> static const struct of_device_id ltc2496_of_match[] = {
> - { .compatible = "lltc,ltc2496", },
> + { .compatible = "lltc,ltc2496", .data = (void *)<c2496_info },
as below. Take the chip_info structure const and drop the cast.
> {},
> };
> 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..bb5e0d4301e2 100644
> --- a/drivers/iio/adc/ltc2497.c
> +++ b/drivers/iio/adc/ltc2497.c
> @@ -7,10 +7,14 @@
> * Datasheet: http://cds.linear.com/docs/en/datasheet/2497fd.pdf
> */
>
> +#include <linux/bitfield.h>
> +#include <linux/bitops.h>
Not immediately obvious why these need adding as part of this patch.
If just general include improvement, separate patch please.
> +
Why blank line?
> #include <linux/i2c.h>
> #include <linux/iio/iio.h>
> #include <linux/iio/driver.h>
> #include <linux/module.h>
> +#include <linux/property.h>
May make sense, but not obvious why it's in this patch.
If it's missing and should be present, please do it in a separate patch.
> #include <linux/mod_devicetable.h>
>
> #include "ltc2497.h"
> @@ -19,6 +23,8 @@ 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.
> @@ -34,13 +40,14 @@ static int ltc2497_result_and_measure(struct ltc2497core_driverdata *ddata,
> int ret;
>
> if (val) {
> - ret = i2c_master_recv(st->client, (char *)&st->buf, 3);
> + ret = i2c_master_recv(st->client, (char *)&st->buf, st->recv_size);
Not helpful yet, but there was a patch series under review form Jason Gerecke that
changed the i2c transfer commands to use a u8.
Which raises a question. buf is a __be32 which is rather odd given size of 3 in original
code. If we have a case where it needs to have separate types for different transfers, use
a union.
> if (ret < 0) {
> dev_err(&st->client->dev, "i2c_master_recv failed\n");
> return ret;
> }
>
> - *val = (be32_to_cpu(st->buf) >> 14) - (1 << 17);
Old code here is less than ideal, should be reading into 3 bytes then using
the be24 accesors. Please fix whilst here. You will need multiple paths here
depending on size.
> + *val = (be32_to_cpu(st->buf) >> st->sub_lsb) -
> + BIT(ddata->chip_info->resolution + 1);
> }
>
> ret = i2c_smbus_write_byte(st->client,
> @@ -54,6 +61,7 @@ static int ltc2497_result_and_measure(struct ltc2497core_driverdata *ddata,
> static int ltc2497_probe(struct i2c_client *client,
> const struct i2c_device_id *id)
> {
> + u32 resolution;
> struct iio_dev *indio_dev;
> struct ltc2497_driverdata *st;
> struct device *dev = &client->dev;
> @@ -70,6 +78,11 @@ static int ltc2497_probe(struct i2c_client *client,
> i2c_set_clientdata(client, indio_dev);
> st->client = client;
> st->common_ddata.result_and_measure = ltc2497_result_and_measure;
> + st->common_ddata.chip_info = device_get_match_data(dev);
> +
> + resolution = st->common_ddata.chip_info->resolution;
> + st->sub_lsb = 31 - (resolution + 1);
> + st->recv_size = resolution / BITS_PER_BYTE + 1;
>
> return ltc2497core_probe(dev, indio_dev);
> }
> @@ -83,15 +96,26 @@ static int ltc2497_remove(struct i2c_client *client)
> return 0;
> }
>
> +static struct chip_info ltc2497_info[] = {
Should be const - which is why you need the cast below.
> + [TYPE_LTC2497] = {
> + .resolution = 16,
> + },
> + [TYPE_LTC2499] = {
> + .resolution = 24,
> + }
> +};
> +
> static const struct i2c_device_id ltc2497_id[] = {
> - { "ltc2497", 0 },
> + { "ltc2497", TYPE_LTC2497 },
> + { "ltc2499", TYPE_LTC2499 },
> { }
> };
> MODULE_DEVICE_TABLE(i2c, ltc2497_id);
>
> static const struct of_device_id ltc2497_of_match[] = {
> - { .compatible = "lltc,ltc2497", },
> - {},
> + { .compatible = "lltc,ltc2497", .data = (void *)<c2497_info[TYPE_LTC2497] },
> + { .compatible = "lltc,ltc2499", .data = (void *)<c2497_info[TYPE_LTC2499] },
Cast is a bad sign. Reason above.
> + {}
> };
> MODULE_DEVICE_TABLE(of, ltc2497_of_match);
>
> diff --git a/drivers/iio/adc/ltc2497.h b/drivers/iio/adc/ltc2497.h
> index d0b42dd6b8ad..f4d939cfd48b 100644
> --- a/drivers/iio/adc/ltc2497.h
> +++ b/drivers/iio/adc/ltc2497.h
> @@ -4,9 +4,20 @@
> #define LTC2497_CONFIG_DEFAULT LTC2497_ENABLE
> #define LTC2497_CONVERSION_TIME_MS 150ULL
>
> +enum chip_type {
> + TYPE_LTC2496,
> + TYPE_LTC2497,
> + TYPE_LTC2499
> +};
> +
> +struct chip_info {
> + u32 resolution;
> +};
> +
> struct ltc2497core_driverdata {
> struct regulator *ref;
> - ktime_t time_prev;
> + ktime_t time_prev;
I'm staring at this and can't see the difference between the two lines.
Closer inspection (i.e. messing with the stuff around it) tells me line
you are removing has a tab when should be a space. Whilst trivial please
call that out in patch description (or do it as a separate patch).
> + const struct chip_info *chip_info;
> u8 addr_prev;
> int (*result_and_measure)(struct ltc2497core_driverdata *ddata,
> u8 address, int *val);
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