On Thu, 1 Sep 2022 15:16:59 +0300 Ciprian Regus <ciprian.regus@xxxxxxxxxx> 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@xxxxxxxxxx> A few small comments inline, but looks pretty good to me. Jonathan > --- > changes in v2: > - removed the bitfield.h and bitops.h includes, since they were not needed. > - removed a blank line. > - replaced the data buffer for the ltc2497_driverdata with a union. > - depending on frame size, i2c transfers use either 3 or 4 byte buffers, instead > of always using a __be32. > - added a comment which explains the output data format and how does sign extension. > happen. > - added the const modifier for the chip_info structs. > - renamed the chip_info struct to ltc2497_chip_info. > - renamed the chip_type enum to ltc2497_chip_type > - added probe fallback to using i2c_device_id in case OF fails. > - used BITS_TO_BYTES() instead of dividing by 8. > - used a tab instead of a space in a struct field declaration, which in v1 appeared as > if the line was deleted and added back. > - added back a trailing comma. > - rearranged variable declaration lines so that longer ones would be first. > - used pointers to a chip info struct in the i2c_device_id table, instead of enums. > drivers/iio/adc/ltc2496.c | 8 ++++- > drivers/iio/adc/ltc2497-core.c | 2 +- > drivers/iio/adc/ltc2497.c | 56 +++++++++++++++++++++++++++++++--- > drivers/iio/adc/ltc2497.h | 11 +++++++ > 4 files changed, 70 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); Hmm. This driver doesn't provide the other i2c registration path (i2c_device_id table) so this is fine. Adding that table can be a problem for whoever needs it sometime in the future (I'm fine with patches to add it though if anyone wants to write one!) > > 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..2f660015f34b 100644 > --- a/drivers/iio/adc/ltc2497.c > +++ b/drivers/iio/adc/ltc2497.c > @@ -12,6 +12,7 @@ > #include <linux/iio/driver.h> > #include <linux/module.h> > #include <linux/mod_devicetable.h> > +#include <linux/property.h> > > #include "ltc2497.h" > > @@ -19,11 +20,16 @@ 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 +40,29 @@ 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. Description looks good to me. Thanks for adding. > + */ > + 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); > + } > } > > > +static const struct ltc2497_chip_info ltc2497_info[] = { > + [TYPE_LTC2497] = { > + .resolution = 16, > + .name = NULL, > + }, > + [TYPE_LTC2499] = { > + .resolution = 24, > + .name = "ltc2499", > + }, > +}; > + > 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_LTC2497] }, TYPE_LTC2499 Guess you haven't tested this particular path but should be easy to force it by not setting the of_device_id table pointer (or you could use a board file but that's more trouble than ti's worth). > { } > }; > 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..95f6a5f4d4a6 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 ltc2497_chip_type { > + TYPE_LTC2496, Hmm. this is a little interesting given there is no such entry in the info table so that table will get pushed out to have an empty first entry. Maybe push this chip_type definition down into the relevant c file and drop the LTC2496 entry (which will then seem fine as that .c file doesn't cover that part. > + TYPE_LTC2497, > + TYPE_LTC2499, > +}; > +
