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Message-ID: <20231221172025.40465cf5@jic23-huawei>
Date: Thu, 21 Dec 2023 17:20:25 +0000
From: Jonathan Cameron <jic23@...nel.org>
To: Dumitru Ceclan <mitrutzceclan@...il.com>
Cc: Lars-Peter Clausen <lars@...afoo.de>, Rob Herring <robh+dt@...nel.org>,
Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>, Conor Dooley
<conor+dt@...nel.org>, linux-iio@...r.kernel.org,
devicetree@...r.kernel.org, linux-kernel@...r.kernel.org, Ceclan Dumitru
<dumitru.ceclan@...log.com>
Subject: Re: [PATCH 3/3] iio: amplifiers: hmc425a: add support for LTC6373
Instrumentation Amplifier
On Thu, 21 Dec 2023 13:38:40 +0200
Dumitru Ceclan <mitrutzceclan@...il.com> wrote:
> This adds support for LTC6373 36 V Fully-Differential Programmable-Gain
> Instrumentation Amplifier with 25 pA Input Bias Current.
> The user can program the gain to one of seven available settings through
> a 3-bit parallel interface (A2 to A0).
>
> Signed-off-by: Dumitru Ceclan <mitrutzceclan@...il.com>
One trivial comment inline.
The use of IIO_INFO_ENABLE is unusual. So far the only documented uses of
that are
What: /sys/.../iio:deviceX/in_energy_en
What: /sys/.../iio:deviceX/in_distance_en
What: /sys/.../iio:deviceX/in_velocity_sqrt(x^2+y^2+z^2)_en
What: /sys/.../iio:deviceX/in_steps_en
KernelVersion: 3.19
Contact: linux-iio@...r.kernel.org
Description:
Activates a device feature that runs in firmware/hardware.
E.g. for steps: the pedometer saves power while not used;
when activated, it will count the steps taken by the user in
firmware and export them through in_steps_input.
And this doesn't match up with these sort of 'counting' or 'cumulative' measures.
I wonder treating it like a DAC output and instead using _powerdown
instead?
---
> drivers/iio/amplifiers/hmc425a.c | 78 +++++++++++++++++++++++++++++++-
> 1 file changed, 76 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/iio/amplifiers/hmc425a.c b/drivers/iio/amplifiers/hmc425a.c
> index b5fd19403d15..27fdc32a0457 100644
> --- a/drivers/iio/amplifiers/hmc425a.c
> +++ b/drivers/iio/amplifiers/hmc425a.c
> @@ -2,9 +2,10 @@
> /*
> * HMC425A and similar Gain Amplifiers
> *
> - * Copyright 2020 Analog Devices Inc.
> + * Copyright 2020, 2023 Analog Devices Inc.
> */
>
> +#include <linux/bits.h>
> #include <linux/bitops.h>
> #include <linux/device.h>
> #include <linux/err.h>
> @@ -20,10 +21,23 @@
> #include <linux/regulator/consumer.h>
> #include <linux/sysfs.h>
>
> +/*
> + * The LTC6373 amplifier supports configuring gain using GPIO's with the following
> + * values (OUTPUT_V / INPUT_V): 0(shutdown), 0.25, 0.5, 1, 2, 4, 8, 16
> + *
> + * Except for the shutdown value, all can be converted to dB using 20 * log10(x)
> + * From here, it is observed that all values are multiples of the '2' gain setting,
> + * with the correspondent of 6.020dB.
> + */
> +#define LTC6373_CONVERSION_CONSTANT 6020
> +#define LTC6373_CONVERSION_MASK GENMASK(2, 0)
> +#define LTC6373_SHUTDOWN GENMASK(2, 0)
> +
> enum hmc425a_type {
> ID_HMC425A,
> ID_HMC540S,
> - ID_ADRF5740
> + ID_ADRF5740,
> + ID_LTC6373,
> };
>
> struct hmc425a_chip_info {
> @@ -42,6 +56,8 @@ struct hmc425a_state {
> struct gpio_descs *gpios;
> enum hmc425a_type type;
> u32 gain;
> + bool enabled;
> +
> };
>
> static int hmc425a_write(struct iio_dev *indio_dev, u32 value)
> @@ -80,6 +96,17 @@ static int hmc425a_gain_dB_to_code(struct hmc425a_state *st, int val, int val2,
> temp = (abs(gain) / 2000) & 0xF;
> *code = temp & BIT(3) ? temp | BIT(2) : temp;
> break;
> + case ID_LTC6373:
> + if (!st->enabled)
> + return -EPERM;
> +
> + /* add half of the value for rounding */
> + temp = LTC6373_CONVERSION_CONSTANT / 2;
> + if (val < 0)
> + temp *= -1;
> + *code = ~((gain + temp) / LTC6373_CONVERSION_CONSTANT + 3)
> + & LTC6373_CONVERSION_MASK;
> + break;
> }
> return 0;
> }
> @@ -100,6 +127,12 @@ static int hmc425a_code_to_gain_dB(struct hmc425a_state *st, int *val, int *val2
> code = code & BIT(3) ? code & ~BIT(2) : code;
> gain = code * -2000;
> break;
> + case ID_LTC6373:
> + if (!st->enabled)
> + return -EPERM;
> + gain = ((~code & LTC6373_CONVERSION_MASK) - 3) *
> + LTC6373_CONVERSION_CONSTANT;
> + break;
> }
>
> *val = gain / 1000;
> @@ -122,6 +155,10 @@ static int hmc425a_read_raw(struct iio_dev *indio_dev,
> break;
> ret = IIO_VAL_INT_PLUS_MICRO_DB;
> break;
> + case IIO_CHAN_INFO_ENABLE:
> + *val = st->enabled;
> + ret = IIO_VAL_INT;
> + break;
> default:
> ret = -EINVAL;
> }
> @@ -146,6 +183,17 @@ static int hmc425a_write_raw(struct iio_dev *indio_dev,
> st->gain = code;
> ret = hmc425a_write(indio_dev, st->gain);
> break;
> + case IIO_CHAN_INFO_ENABLE:
> + switch (st->type) {
> + case ID_LTC6373:
> + code = (val) ? st->gain : LTC6373_SHUTDOWN;
> + st->enabled = val;
> + ret = hmc425a_write(indio_dev, code);
> + break;
> + default:
> + ret = -EINVAL;
> + }
> + break;
> default:
> ret = -EINVAL;
> }
> @@ -161,6 +209,8 @@ static int hmc425a_write_raw_get_fmt(struct iio_dev *indio_dev,
> switch (mask) {
> case IIO_CHAN_INFO_HARDWAREGAIN:
> return IIO_VAL_INT_PLUS_MICRO_DB;
> + case IIO_CHAN_INFO_ENABLE:
> + return IIO_VAL_INT;
> default:
> return -EINVAL;
> }
> @@ -181,15 +231,30 @@ static const struct iio_info hmc425a_info = {
> .info_mask_separate = BIT(IIO_CHAN_INFO_HARDWAREGAIN), \
> }
>
> +#define LTC6373_CHAN(_channel) \
> +{ \
> + .type = IIO_VOLTAGE, \
> + .output = 1, \
> + .indexed = 1, \
> + .channel = _channel, \
> + .info_mask_separate = BIT(IIO_CHAN_INFO_HARDWAREGAIN) | \
> + BIT(IIO_CHAN_INFO_ENABLE), \
> +}
> +
> static const struct iio_chan_spec hmc425a_channels[] = {
> HMC425A_CHAN(0),
> };
>
> +static const struct iio_chan_spec ltc6373_channels[] = {
> + LTC6373_CHAN(0),
> +};
> +
> /* Match table for of_platform binding */
> static const struct of_device_id hmc425a_of_match[] = {
> { .compatible = "adi,hmc425a", .data = (void *)ID_HMC425A },
> { .compatible = "adi,hmc540s", .data = (void *)ID_HMC540S },
> { .compatible = "adi,adrf5740", .data = (void *)ID_ADRF5740 },
> + { .compatible = "adi,ltc6373", .data = (void *)ID_LTC6373 },
> {},
> };
> MODULE_DEVICE_TABLE(of, hmc425a_of_match);
> @@ -222,6 +287,15 @@ static struct hmc425a_chip_info hmc425a_chip_info_tbl[] = {
> .gain_max = 0,
> .default_gain = 0xF, /* set default gain -22.0db*/
> },
> + [ID_LTC6373] = {
Looks to be one tab too far indented.
> + .name = "ltc6373",
> + .channels = ltc6373_channels,
> + .num_channels = ARRAY_SIZE(ltc6373_channels),
> + .num_gpios = 3,
> + .gain_min = -12041, /* gain setting x0.25*/
> + .gain_max = 24082, /* gain setting x16 */
> + .default_gain = LTC6373_SHUTDOWN,
> + },
> };
>
> static int hmc425a_probe(struct platform_device *pdev)
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