Date:   Sun, 9 Jan 2022 17:29:48 +0000
From:   Jonathan Cameron <jic23@jic23.retrosnub.co.uk>
To:     Caleb Connolly <caleb.connolly@linaro.org>
Cc:     Lars-Peter Clausen <lars@metafoo.de>,
        Rob Herring <robh+dt@kernel.org>,
        Andy Gross <agross@kernel.org>,
        Bjorn Andersson <bjorn.andersson@linaro.org>,
        Lee Jones <lee.jones@linaro.org>, linux-iio@vger.kernel.org,
        devicetree@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-arm-msm@vger.kernel.org, sumit.semwal@linaro.org,
        amit.pundir@linaro.org, john.stultz@linaro.org
Subject: Re: [PATCH v3 3/7] iio: adc: qcom-spmi-rradc: introduce round robin
 adc
Message-ID: <20220109172948.76dbb1fa@jic23-huawei>
In-Reply-To: <20220106173131.3279580-4-caleb.connolly@linaro.org>
References: <20220106173131.3279580-1-caleb.connolly@linaro.org>
        <20220106173131.3279580-4-caleb.connolly@linaro.org>
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On Thu,  6 Jan 2022 17:31:27 +0000
Caleb Connolly <caleb.connolly@linaro.org> wrote:

> The Round Robin ADC is responsible for reading data about the rate of
> charge from the USB or DC in jacks, it can also read the battery
> ID (resistence) and some temperatures. It is found on the PMI8998 and
> PM660 Qualcomm PMICs.
> 
> Signed-off-by: Caleb Connolly <caleb.connolly@linaro.org>
Hi Calib,

Various things inline but biggest is probably that in IIO we prefer
if possible to make application of offsets and scales a job for the caller,
either userspace or in kernel callers. This allows them to maintain precision
better if they need to further transform the data.

Jonathan

> ---
>  drivers/iio/adc/Kconfig           |   13 +
>  drivers/iio/adc/Makefile          |    1 +
>  drivers/iio/adc/qcom-spmi-rradc.c | 1070 +++++++++++++++++++++++++++++
>  3 files changed, 1084 insertions(+)
>  create mode 100644 drivers/iio/adc/qcom-spmi-rradc.c
> 
> diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
> index 3363af15a43f..37f18ee4c4c5 100644
> --- a/drivers/iio/adc/Kconfig
> +++ b/drivers/iio/adc/Kconfig
> @@ -812,6 +812,19 @@ config QCOM_PM8XXX_XOADC
>  	  To compile this driver as a module, choose M here: the module
>  	  will be called qcom-pm8xxx-xoadc.
>  
> +config QCOM_SPMI_RRADC
> +	tristate "Qualcomm SPMI RRADC"
> +	depends on MFD_SPMI_PMIC
> +	help
> +	  This is for the PMIC Round Robin ADC driver.
> +
> +	  This driver exposes the battery ID resistor, battery thermal, PMIC die
> +	  temperature, charger USB in and DC in voltage and current.
> +
> +	  To compile this driver as a module, choose M here: the module will
> +	  be called qcom-qpmi-rradc.
> +
> +
>  config QCOM_SPMI_IADC
>  	tristate "Qualcomm SPMI PMIC current ADC"
>  	depends on SPMI
> diff --git a/drivers/iio/adc/Makefile b/drivers/iio/adc/Makefile
> index d3f53549720c..ca8bad549175 100644
> --- a/drivers/iio/adc/Makefile
> +++ b/drivers/iio/adc/Makefile
> @@ -77,6 +77,7 @@ obj-$(CONFIG_NPCM_ADC) += npcm_adc.o
>  obj-$(CONFIG_PALMAS_GPADC) += palmas_gpadc.o
>  obj-$(CONFIG_QCOM_SPMI_ADC5) += qcom-spmi-adc5.o
>  obj-$(CONFIG_QCOM_SPMI_IADC) += qcom-spmi-iadc.o
> +obj-$(CONFIG_QCOM_SPMI_RRADC) += qcom-spmi-rradc.o
>  obj-$(CONFIG_QCOM_VADC_COMMON) += qcom-vadc-common.o
>  obj-$(CONFIG_QCOM_SPMI_VADC) += qcom-spmi-vadc.o
>  obj-$(CONFIG_QCOM_PM8XXX_XOADC) += qcom-pm8xxx-xoadc.o
> diff --git a/drivers/iio/adc/qcom-spmi-rradc.c b/drivers/iio/adc/qcom-spmi-rradc.c
> new file mode 100644
> index 000000000000..d07426d04161
> --- /dev/null
> +++ b/drivers/iio/adc/qcom-spmi-rradc.c
> @@ -0,0 +1,1070 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Copyright (c) 2021 Linaro Limited.
> + *  Author: Caleb Connolly <caleb.connolly@linaro.org>
> + *
> + * This driver is for the Round Robin ADC found in the pmi8998 and pm660 PMICs.
> + */
> +
> +#include <linux/bitfield.h>
> +#include <linux/delay.h>
> +#include <linux/iio/iio.h>
> +#include <linux/iio/types.h>
> +#include <linux/kernel.h>
> +#include <linux/math64.h>
> +#include <linux/minmax.h>
?

> +#include <linux/module.h>
> +#include <linux/of.h>
Why include of.h? You've correctly used the stuff in property.h
#include <linux/mod_devicetable.h> is what to include for the id table.


> +#include <linux/platform_device.h>
> +#include <linux/power_supply.h>
?

> +#include <linux/regmap.h>
> +#include <linux/spmi.h>
> +#include <linux/types.h>
> +#include <asm-generic/unaligned.h>

Convention is to put the asm stuff after linux includes.

> +#include <linux/units.h>
> +#include <soc/qcom/qcom-pmic.h>
> +
> +#define RR_ADC_EN_CTL 0x46
> +#define RR_ADC_SKIN_TEMP_LSB 0x50
> +#define RR_ADC_SKIN_TEMP_MSB 0x51
> +#define RR_ADC_RR_ADC_CTL 0x52

Name seems inconsistent with the field naming that follows.

> +#define RR_ADC_ADC_CTL_CONTINUOUS_SEL BIT(3)
> +#define RR_ADC_ADC_LOG 0x53
> +#define RR_ADC_ADC_LOG_CLR_CTRL BIT(0)
> +
> +#define RR_ADC_FAKE_BATT_LOW_LSB 0x58
> +#define RR_ADC_FAKE_BATT_LOW_MSB 0x59
> +#define RR_ADC_FAKE_BATT_HIGH_LSB 0x5A
> +#define RR_ADC_FAKE_BATT_HIGH_MSB 0x5B
> +
> +#define RR_ADC_BATT_ID_CTRL 0x60
> +#define RR_ADC_BATT_ID_CTRL_CHANNEL_CONV BIT(0)
> +#define RR_ADC_BATT_ID_TRIGGER 0x61
> +#define RR_ADC_BATT_ID_STS 0x62
> +#define RR_ADC_BATT_ID_CFG 0x63
> +#define BATT_ID_SETTLE_MASK GENMASK(7, 5)
> +#define RR_ADC_BATT_ID_5_LSB 0x66
> +#define RR_ADC_BATT_ID_5_MSB 0x67
> +#define RR_ADC_BATT_ID_15_LSB 0x68
> +#define RR_ADC_BATT_ID_15_MSB 0x69
> +#define RR_ADC_BATT_ID_150_LSB 0x6A
> +#define RR_ADC_BATT_ID_150_MSB 0x6B
> +
> +#define RR_ADC_BATT_THERM_CTRL 0x70
> +#define RR_ADC_BATT_THERM_TRIGGER 0x71
> +#define RR_ADC_BATT_THERM_STS 0x72
> +#define RR_ADC_BATT_THERM_CFG 0x73
> +#define RR_ADC_BATT_THERM_LSB 0x74
> +#define RR_ADC_BATT_THERM_MSB 0x75
> +#define RR_ADC_BATT_THERM_FREQ 0x76
> +
> +#define RR_ADC_AUX_THERM_CTRL 0x80
> +#define RR_ADC_AUX_THERM_TRIGGER 0x81
> +#define RR_ADC_AUX_THERM_STS 0x82
> +#define RR_ADC_AUX_THERM_CFG 0x83
> +#define RR_ADC_AUX_THERM_LSB 0x84
> +#define RR_ADC_AUX_THERM_MSB 0x85
> +
> +#define RR_ADC_SKIN_HOT 0x86
> +#define RR_ADC_SKIN_TOO_HOT 0x87
> +
> +#define RR_ADC_AUX_THERM_C1 0x88
> +#define RR_ADC_AUX_THERM_C2 0x89
> +#define RR_ADC_AUX_THERM_C3 0x8A
> +#define RR_ADC_AUX_THERM_HALF_RANGE 0x8B
> +
> +#define RR_ADC_USB_IN_V_CTRL 0x90
> +#define RR_ADC_USB_IN_V_TRIGGER 0x91
> +#define RR_ADC_USB_IN_V_STS 0x92
> +#define RR_ADC_USB_IN_V_LSB 0x94
> +#define RR_ADC_USB_IN_V_MSB 0x95
> +#define RR_ADC_USB_IN_I_CTRL 0x98
> +#define RR_ADC_USB_IN_I_TRIGGER 0x99
> +#define RR_ADC_USB_IN_I_STS 0x9A
> +#define RR_ADC_USB_IN_I_LSB 0x9C
> +#define RR_ADC_USB_IN_I_MSB 0x9D
> +
> +#define RR_ADC_DC_IN_V_CTRL 0xA0
> +#define RR_ADC_DC_IN_V_TRIGGER 0xA1
> +#define RR_ADC_DC_IN_V_STS 0xA2
> +#define RR_ADC_DC_IN_V_LSB 0xA4
> +#define RR_ADC_DC_IN_V_MSB 0xA5
> +#define RR_ADC_DC_IN_I_CTRL 0xA8
> +#define RR_ADC_DC_IN_I_TRIGGER 0xA9
> +#define RR_ADC_DC_IN_I_STS 0xAA
> +#define RR_ADC_DC_IN_I_LSB 0xAC
> +#define RR_ADC_DC_IN_I_MSB 0xAD
> +
> +#define RR_ADC_PMI_DIE_TEMP_CTRL 0xB0
> +#define RR_ADC_PMI_DIE_TEMP_TRIGGER 0xB1
> +#define RR_ADC_PMI_DIE_TEMP_STS 0xB2
> +#define RR_ADC_PMI_DIE_TEMP_CFG 0xB3
> +#define RR_ADC_PMI_DIE_TEMP_LSB 0xB4
> +#define RR_ADC_PMI_DIE_TEMP_MSB 0xB5
> +
> +#define RR_ADC_CHARGER_TEMP_CTRL 0xB8
> +#define RR_ADC_CHARGER_TEMP_TRIGGER 0xB9
> +#define RR_ADC_CHARGER_TEMP_STS 0xBA
> +#define RR_ADC_CHARGER_TEMP_CFG 0xBB
> +#define RR_ADC_CHARGER_TEMP_LSB 0xBC
> +#define RR_ADC_CHARGER_TEMP_MSB 0xBD
> +#define RR_ADC_CHARGER_HOT 0xBE
> +#define RR_ADC_CHARGER_TOO_HOT 0xBF
> +
> +#define RR_ADC_GPIO_CTRL 0xC0
> +#define RR_ADC_GPIO_TRIGGER 0xC1
> +#define RR_ADC_GPIO_STS 0xC2
> +#define RR_ADC_GPIO_LSB 0xC4
> +#define RR_ADC_GPIO_MSB 0xC5
> +
> +#define RR_ADC_ATEST_CTRL 0xC8
> +#define RR_ADC_ATEST_TRIGGER 0xC9
> +#define RR_ADC_ATEST_STS 0xCA
> +#define RR_ADC_ATEST_LSB 0xCC
> +#define RR_ADC_ATEST_MSB 0xCD
> +#define RR_ADC_SEC_ACCESS 0xD0
> +
> +#define RR_ADC_PERPH_RESET_CTL2 0xD9
> +#define RR_ADC_PERPH_RESET_CTL3 0xDA
> +#define RR_ADC_PERPH_RESET_CTL4 0xDB
> +#define RR_ADC_INT_TEST1 0xE0
> +#define RR_ADC_INT_TEST_VAL 0xE1
> +
> +#define RR_ADC_TM_TRIGGER_CTRLS 0xE2
> +#define RR_ADC_TM_ADC_CTRLS 0xE3
> +#define RR_ADC_TM_CNL_CTRL 0xE4
> +#define RR_ADC_TM_BATT_ID_CTRL 0xE5
> +#define RR_ADC_TM_THERM_CTRL 0xE6
> +#define RR_ADC_TM_CONV_STS 0xE7
> +#define RR_ADC_TM_ADC_READ_LSB 0xE8
> +#define RR_ADC_TM_ADC_READ_MSB 0xE9
> +#define RR_ADC_TM_ATEST_MUX_1 0xEA
> +#define RR_ADC_TM_ATEST_MUX_2 0xEB
> +#define RR_ADC_TM_REFERENCES 0xED
> +#define RR_ADC_TM_MISC_CTL 0xEE
> +#define RR_ADC_TM_RR_CTRL 0xEF
> +
> +#define RR_ADC_TRIGGER_EVERY_CYCLE BIT(7)
> +#define RR_ADC_TRIGGER_CTL BIT(0)
> +
> +#define RR_ADC_BATT_ID_RANGE 820
> +
> +#define RR_ADC_BITS 10
> +#define RR_ADC_CHAN_MAX_VALUE (1 << RR_ADC_BITS)
> +#define RR_ADC_FS_VOLTAGE_MV 2500
> +
> +/* BATT_THERM 0.25K/LSB */
> +#define RR_ADC_BATT_THERM_LSB_K 4
> +
> +#define RR_ADC_TEMP_FS_VOLTAGE_NUM 5000000
> +#define RR_ADC_TEMP_FS_VOLTAGE_DEN 3
> +#define RR_ADC_DIE_TEMP_OFFSET 601400
> +#define RR_ADC_DIE_TEMP_SLOPE 2
> +#define RR_ADC_DIE_TEMP_OFFSET_MILLI_DEGC 25000
> +
> +#define RR_ADC_CHG_TEMP_GF_OFFSET_UV 1303168
> +#define RR_ADC_CHG_TEMP_GF_SLOPE_UV_PER_C 3784
> +#define RR_ADC_CHG_TEMP_SMIC_OFFSET_UV 1338433
> +#define RR_ADC_CHG_TEMP_SMIC_SLOPE_UV_PER_C 3655
> +#define RR_ADC_CHG_TEMP_660_GF_OFFSET_UV 1309001
> +#define RR_ADC_CHG_TEMP_660_GF_SLOPE_UV_PER_C 3403
> +#define RR_ADC_CHG_TEMP_660_SMIC_OFFSET_UV 1295898
> +#define RR_ADC_CHG_TEMP_660_SMIC_SLOPE_UV_PER_C 3596
> +#define RR_ADC_CHG_TEMP_660_MGNA_OFFSET_UV 1314779
> +#define RR_ADC_CHG_TEMP_660_MGNA_SLOPE_UV_PER_C 3496
> +#define RR_ADC_CHG_TEMP_OFFSET_MILLI_DEGC 25000
> +#define RR_ADC_CHG_THRESHOLD_SCALE 4
> +
> +#define RR_ADC_VOLT_INPUT_FACTOR 8
> +#define RR_ADC_CURR_INPUT_FACTOR 2000
> +#define RR_ADC_CURR_USBIN_INPUT_FACTOR_MIL 1886
> +#define RR_ADC_CURR_USBIN_660_FACTOR_MIL 9
> +#define RR_ADC_CURR_USBIN_660_UV_VAL 579500
> +
> +#define RR_ADC_GPIO_FS_RANGE 5000
> +#define RR_ADC_COHERENT_CHECK_RETRY 5
> +#define RR_ADC_CHAN_MAX_CONTINUOUS_BUFFER_LEN 16
> +
> +#define RR_ADC_STS_CHANNEL_READING_MASK 0x3
> +#define RR_ADC_STS_CHANNEL_STS 0x2
> +
> +#define RR_ADC_TP_REV_VERSION1 21
> +#define RR_ADC_TP_REV_VERSION2 29
> +#define RR_ADC_TP_REV_VERSION3 32
> +
> +#define RRADC_BATT_ID_DELAY_MAX 8
> +
> +enum rradc_channel_id {
> +	RR_ADC_BATT_ID = 0,
> +	RR_ADC_BATT_THERM,
> +	RR_ADC_SKIN_TEMP,
> +	RR_ADC_USBIN_I,
> +	RR_ADC_USBIN_V,
> +	RR_ADC_DCIN_I,
> +	RR_ADC_DCIN_V,
> +	RR_ADC_DIE_TEMP,
> +	RR_ADC_CHG_TEMP,
> +	RR_ADC_GPIO,
> +	RR_ADC_CHG_HOT_TEMP,
> +	RR_ADC_CHG_TOO_HOT_TEMP,
> +	RR_ADC_SKIN_HOT_TEMP,
> +	RR_ADC_SKIN_TOO_HOT_TEMP,
> +	RR_ADC_CHAN_MAX
> +};
> +
> +struct rradc_chip;
> +
> +/**
> + * struct rradc_channel - rradc channel data
> + * @lsb:		Channel least significant byte
> + * @status:		Channel status address
> + * @size:		number of bytes to read
> + * @trigger_addr:	Trigger address, trigger is only used on some channels
> + * @trigger_mask:	Trigger mask
> + * @scale:		Channel scale callback
> + */
> +struct rradc_channel {
> +	u8 lsb;
> +	u8 status;
> +	int size;
> +	int trigger_addr;
> +	int trigger_mask;
> +	int (*scale)(struct rradc_chip *chip, u16 adc_code, int *result);
> +};
> +
> +struct rradc_chip {
> +	struct device *dev;
> +	struct qcom_spmi_pmic *pmic;
> +	struct mutex lock;

Locks always need a comment to say what their scope is.

> +	struct regmap *regmap;
> +	u32 base;
> +	int batt_id_delay;
> +	u16 batt_id_data;
> +};
> +
> +static const int batt_id_delays[] = { 0, 1, 4, 12, 20, 40, 60, 80 };
> +static const struct rradc_channel rradc_chans[RR_ADC_CHAN_MAX];
> +static const struct iio_chan_spec rradc_iio_chans[RR_ADC_CHAN_MAX];
> +
> +static int rradc_read(struct rradc_chip *chip, u16 addr, u8 *data, int len)
> +{
> +	int ret, retry_cnt = 0;
> +	u8 data_check[RR_ADC_CHAN_MAX_CONTINUOUS_BUFFER_LEN];
> +
> +	if (len > RR_ADC_CHAN_MAX_CONTINUOUS_BUFFER_LEN) {
> +		dev_err(chip->dev,
> +			"Can't read more than %d bytes, but asked to read %d bytes.\n",
> +			RR_ADC_CHAN_MAX_CONTINUOUS_BUFFER_LEN, len);
> +		return -EINVAL;
> +	}
> +
> +	while (retry_cnt < RR_ADC_COHERENT_CHECK_RETRY) {
> +		ret = regmap_bulk_read(chip->regmap, chip->base + addr, data,
> +				       len);
> +		if (ret < 0) {
> +			dev_err(chip->dev, "rr_adc reg 0x%x failed :%d\n", addr,
> +				ret);
> +			return ret;
> +		}
> +
> +		ret = regmap_bulk_read(chip->regmap, chip->base + addr,
> +				       data_check, len);
> +		if (ret < 0) {
> +			dev_err(chip->dev, "rr_adc reg 0x%x failed :%d\n", addr,
> +				ret);
> +			return ret;
> +		}
> +
> +		if (memcmp(data, data_check, len) != 0) {
> +			retry_cnt++;
> +			dev_dbg(chip->dev,
> +				"coherent read error, retry_cnt:%d\n",
> +				retry_cnt);
> +			continue;
> +		}
> +
> +		break;
> +	}
> +
> +	if (retry_cnt == RR_ADC_COHERENT_CHECK_RETRY)
> +		dev_err(chip->dev, "Retry exceeded for coherrency check\n");
> +
> +	return ret;
> +}
> +
> +static int rradc_get_fab_coeff(struct rradc_chip *chip, int64_t *offset,
> +			       int64_t *slope)
> +{
> +	if (chip->pmic->subtype == PM660_SUBTYPE) {
> +		switch (chip->pmic->fab_id) {
> +		case PM660_FAB_ID_GF:
> +			*offset = RR_ADC_CHG_TEMP_660_GF_OFFSET_UV;
> +			*slope = RR_ADC_CHG_TEMP_660_GF_SLOPE_UV_PER_C;
> +			break;
> +		case PM660_FAB_ID_TSMC:
> +			*offset = RR_ADC_CHG_TEMP_660_SMIC_OFFSET_UV;
> +			*slope = RR_ADC_CHG_TEMP_660_SMIC_SLOPE_UV_PER_C;
> +			break;
> +		default:
> +			*offset = RR_ADC_CHG_TEMP_660_MGNA_OFFSET_UV;
> +			*slope = RR_ADC_CHG_TEMP_660_MGNA_SLOPE_UV_PER_C;
> +		}
> +	} else if (chip->pmic->subtype == PMI8998_SUBTYPE) {
> +		switch (chip->pmic->fab_id) {
> +		case PMI8998_FAB_ID_GF:
> +			*offset = RR_ADC_CHG_TEMP_GF_OFFSET_UV;
> +			*slope = RR_ADC_CHG_TEMP_GF_SLOPE_UV_PER_C;
> +			break;
> +		case PMI8998_FAB_ID_SMIC:
> +			*offset = RR_ADC_CHG_TEMP_SMIC_OFFSET_UV;
> +			*slope = RR_ADC_CHG_TEMP_SMIC_SLOPE_UV_PER_C;
> +			break;
> +		default:
> +			return -EINVAL;
> +		}
> +	} else {
> +		return -EINVAL;
> +	}
> +
> +	return 0;
> +}
> +
> +/*
> + * These functions explicitly cast int64_t to int.
> + * They will never overflow, as the values are small enough.
> + */
> +static int rradc_post_process_batt_id(struct rradc_chip *chip, u16 adc_code,
> +				      int *result_ohms)
> +{
> +	uint32_t current_value;
> +	int64_t r_id;
> +
> +	current_value = chip->batt_id_data;
> +	r_id = ((int64_t)adc_code * RR_ADC_FS_VOLTAGE_MV);
> +	r_id = div64_s64(r_id, (RR_ADC_CHAN_MAX_VALUE * current_value));
> +	*result_ohms = (int)(r_id * MILLI);
> +
> +	return 0;
> +}
> +
> +static int rradc_post_process_therm(struct rradc_chip *chip, u16 adc_code,
> +				    int *result_millidegc)
> +{
> +	int64_t temp;
> +
> +	/* K = code/4 */
> +	temp = ((int64_t)adc_code * MILLI);
> +	temp = div64_s64(temp, RR_ADC_BATT_THERM_LSB_K);
> +	*result_millidegc = (int)milli_kelvin_to_millicelsius(temp);
> +
> +	return 0;
> +}
> +
> +static int rradc_post_process_volt(struct rradc_chip *chip, u16 adc_code,
> +				   int *result_uv)
> +{
> +	int64_t uv;
> +
> +	/* 8x input attenuation; 2.5V ADC full scale */
> +	uv = ((int64_t)adc_code * RR_ADC_VOLT_INPUT_FACTOR);
> +	uv *= (RR_ADC_FS_VOLTAGE_MV * MILLI);
> +	uv = div64_s64(uv, RR_ADC_CHAN_MAX_VALUE);
> +	*result_uv = (int)uv;
> +
> +	return 0;
> +}
> +
> +static int rradc_post_process_usbin_curr(struct rradc_chip *chip, u16 adc_code,
> +					 int *result_ua)
> +{
> +	int64_t ua;
> +
> +	/* scale * V/A; 2.5V ADC full scale */
> +	ua = ((int64_t)adc_code * RR_ADC_CURR_USBIN_INPUT_FACTOR_MIL);
> +	ua *= (RR_ADC_FS_VOLTAGE_MV * MILLI);
> +	ua = div64_s64(ua, (RR_ADC_CHAN_MAX_VALUE * 10));
> +	*result_ua = (int)ua;
> +
> +	return 0;
> +}
> +
> +static int rradc_post_process_dcin_curr(struct rradc_chip *chip, u16 adc_code,
> +					int *result_ua)
> +{
> +	int64_t ua;
> +
> +	/* 0.5 V/A; 2.5V ADC full scale */
> +	ua = ((int64_t)adc_code * RR_ADC_CURR_INPUT_FACTOR);
> +	ua *= (RR_ADC_FS_VOLTAGE_MV * MILLI);
> +	ua = div64_s64(ua, (RR_ADC_CHAN_MAX_VALUE * 1000));
> +	*result_ua = (int)ua;
> +
> +	return 0;
> +}
> +
> +static int rradc_post_process_die_temp(struct rradc_chip *chip, u16 adc_code,
> +				       int *result_millidegc)
> +{
> +	int64_t temp;
> +
> +	temp = ((int64_t)adc_code * RR_ADC_TEMP_FS_VOLTAGE_NUM);
> +	temp = div64_s64(temp,
> +			 (RR_ADC_TEMP_FS_VOLTAGE_DEN * RR_ADC_CHAN_MAX_VALUE));
> +	temp -= RR_ADC_DIE_TEMP_OFFSET;
> +	temp = div64_s64(temp, RR_ADC_DIE_TEMP_SLOPE);
> +	temp += RR_ADC_DIE_TEMP_OFFSET_MILLI_DEGC;
> +	*result_millidegc = (int)temp;
> +
> +	return 0;
> +}
> +
> +static int rradc_post_process_chg_temp_hot(struct rradc_chip *chip,
> +					   u16 adc_code, int *result_millidegc)
> +{
> +	int64_t uv, offset, slope;
> +	int ret;
> +
> +	ret = rradc_get_fab_coeff(chip, &offset, &slope);
> +	if (ret < 0) {
> +		dev_err(chip->dev, "Unable to get fab id coefficients\n");
> +		return -EINVAL;
> +	}
> +
> +	uv = (int64_t)adc_code * RR_ADC_CHG_THRESHOLD_SCALE;
> +	uv = uv * RR_ADC_TEMP_FS_VOLTAGE_NUM;
> +	uv = div64_s64(uv,
> +		       (RR_ADC_TEMP_FS_VOLTAGE_DEN * RR_ADC_CHAN_MAX_VALUE));
> +	uv = offset - uv;
> +	uv = div64_s64((uv * MILLI), slope);
> +	uv = uv + RR_ADC_CHG_TEMP_OFFSET_MILLI_DEGC;
> +	*result_millidegc = (int)uv;
> +
> +	return 0;
> +}
> +
> +static int rradc_post_process_skin_temp_hot(struct rradc_chip *chip,
> +					    u16 adc_code, int *result_millidegc)
> +{
> +	int64_t temp;
> +
> +	temp = (int64_t)adc_code;
> +	temp = (div64_s64(temp, 2) - 30) * MILLI;
> +	*result_millidegc = (int)temp;
> +
> +	return 0;
> +}
> +
> +static int rradc_post_process_chg_temp(struct rradc_chip *chip, u16 adc_code,
> +				       int *result_millidegc)
> +{
> +	int64_t uv, offset, slope;
> +	int ret;
> +
> +	ret = rradc_get_fab_coeff(chip, &offset, &slope);
> +	if (ret < 0) {
> +		dev_err(chip->dev, "Unable to get fab id coefficients\n");
> +		return -EINVAL;
> +	}
> +
> +	uv = ((int64_t)adc_code * RR_ADC_TEMP_FS_VOLTAGE_NUM);
> +	uv = div64_s64(uv,
> +		       (RR_ADC_TEMP_FS_VOLTAGE_DEN * RR_ADC_CHAN_MAX_VALUE));
> +	uv = offset - uv;
> +	uv = div64_s64((uv * MILLI), slope);
> +	uv += RR_ADC_CHG_TEMP_OFFSET_MILLI_DEGC;
> +	*result_millidegc = (int)uv;

Marginally harder than the one below, but this is still looking like it can
be well expressed as an offset + scale.  Thus making the tedious maths
userspaces or callers problem.  I'm working backwards hence won't comment on
similar before this point. Key is to transform whatever maths you have into

(adc_code + offset) * scale then expose offset and scale as well as the
raw value.  The right maths will get done for in kernel users and
userspace can do it nicely with floating point.

> +
> +	return 0;
> +}
> +
> +static int rradc_post_process_gpio(struct rradc_chip *chip, u16 adc_code,
> +				   int *result_mv)
> +{
> +	int64_t mv;
> +
> +	/* 5V ADC full scale, 10 bit */
> +	mv = ((int64_t)adc_code * RR_ADC_GPIO_FS_RANGE);

10 bit * 5000 doesn't need 64 bit maths.

> +	mv = div64_s64(mv, RR_ADC_CHAN_MAX_VALUE);
> +	*result_mv = (int)mv;

This is a linear transform.  So much better to present it as _RAW and _SCALE
so that the any in kernel users can decide whether they need to do the calculation
+ can maintain precision if they are scaling it further.

> +
> +	return 0;
> +}
> +
> +static int rradc_enable_continuous_mode(struct rradc_chip *chip)
> +{
> +	int ret;
> +
> +	/* Clear channel log */
> +	ret = regmap_update_bits(chip->regmap, chip->base + RR_ADC_ADC_LOG,
> +				 RR_ADC_ADC_LOG_CLR_CTRL,
> +				 RR_ADC_ADC_LOG_CLR_CTRL);
> +	if (ret < 0) {
> +		dev_err(chip->dev, "log ctrl update to clear failed:%d\n", ret);
> +		return ret;
> +	}
> +
> +	ret = regmap_update_bits(chip->regmap, chip->base + RR_ADC_ADC_LOG,
> +				 RR_ADC_ADC_LOG_CLR_CTRL, 0);
> +	if (ret < 0) {
> +		dev_err(chip->dev, "log ctrl update to not clear failed:%d\n",
> +			ret);
> +		return ret;
> +	}
> +
> +	/* Switch to continuous mode */
> +	ret = regmap_update_bits(chip->regmap, chip->base + RR_ADC_RR_ADC_CTL,
> +				 RR_ADC_ADC_CTL_CONTINUOUS_SEL,
> +				 RR_ADC_ADC_CTL_CONTINUOUS_SEL);
> +	if (ret < 0)
> +		dev_err(chip->dev, "Update to continuous mode failed:%d\n",
> +			ret);
> +
> +	return ret;
> +}
> +
> +static int rradc_disable_continuous_mode(struct rradc_chip *chip)
> +{
> +	int ret;
> +
> +	/* Switch to non continuous mode */
> +	ret = regmap_update_bits(chip->regmap, chip->base + RR_ADC_RR_ADC_CTL,
> +				 RR_ADC_ADC_CTL_CONTINUOUS_SEL, 0);
> +	if (ret < 0)
> +		dev_err(chip->dev, "Update to non-continuous mode failed:%d\n",
> +			ret);
> +
> +	return ret;
> +}
> +
> +static bool rradc_is_ready(struct rradc_chip *chip,
> +			   enum rradc_channel_id chan_id)
> +{
> +	const struct rradc_channel *chan = &rradc_chans[chan_id];
> +	int ret;
> +	unsigned int status, mask;
> +
> +	/* BATT_ID STS bit does not get set initially */
> +	switch (chan_id) {
> +	case RR_ADC_BATT_ID:
> +		mask = RR_ADC_STS_CHANNEL_STS;
> +		break;
> +	default:
> +		mask = RR_ADC_STS_CHANNEL_READING_MASK;
> +		break;
> +	}
> +
> +	ret = regmap_read(chip->regmap, chip->base + chan->status, &status);
> +	if (ret < 0 || !(status & mask))
> +		return false;

I'm assuming that ret < 0 is a rather more serious failure than just
not ready?  If so handle that one separately. At very least print a message
rather than treating it as if the status bit wasn't set.  Ideally handle
it like any other error and return it all the way to userspace.

> +
> +	return true;
> +}
> +
> +static int rradc_read_status_in_cont_mode(struct rradc_chip *chip,
> +					  enum rradc_channel_id chan_id)
> +{
> +	const struct rradc_channel *chan = &rradc_chans[chan_id];
> +	const struct iio_chan_spec *iio_chan = &rradc_iio_chans[chan_id];
> +	int ret, i;
> +
> +	if (chan->trigger_mask == 0) {
> +		dev_err(chip->dev, "Channel doesn't have a trigger mask\n");
> +		return -EINVAL;
> +	}
> +
> +	ret = regmap_update_bits(chip->regmap, chip->base + chan->trigger_addr,
> +				 chan->trigger_mask, chan->trigger_mask);
> +	if (ret < 0) {
> +		dev_err(chip->dev,
> +			"Failed to apply trigger for channel '%s' ret=%d\n",
> +			iio_chan->extend_name, ret);
> +		return ret;
> +	}
> +
> +	ret = rradc_enable_continuous_mode(chip);
> +	if (ret < 0) {
> +		dev_err(chip->dev, "Failed to switch to continuous mode\n");
> +		goto disable_trigger;
> +	}
> +
> +	/*
> +	 * The wait/sleep values were found through trial and error,
> +	 * this is mostly for the battery ID channel which takes some
> +	 * time to settle.
> +	 */
> +	for (i = 0; i < 5; i++) {
> +		if (rradc_is_ready(chip, chan_id))
> +			break;
> +		usleep_range(50000, 50000 + 500);
> +	}
> +
> +	if (i == 5) {
> +		dev_err(chip->dev, "Channel '%s' is not ready\n",
> +			iio_chan->extend_name);
> +		ret = -EINVAL;
> +	}
> +
> +	rradc_disable_continuous_mode(chip);
> +
> +disable_trigger:
> +	regmap_update_bits(chip->regmap, chip->base + chan->trigger_addr,
> +				 chan->trigger_mask, 0);
> +
> +	return ret;
> +}
> +
> +static int rradc_prepare_batt_id_conversion(struct rradc_chip *chip,
> +					    enum rradc_channel_id chan_id,
> +					    u16 *data)
> +{
> +	int ret, batt_id_delay;
> +
> +	ret = regmap_update_bits(chip->regmap, chip->base + RR_ADC_BATT_ID_CTRL,
> +				 RR_ADC_BATT_ID_CTRL_CHANNEL_CONV,
> +				 RR_ADC_BATT_ID_CTRL_CHANNEL_CONV);
> +	if (ret < 0) {
> +		dev_err(chip->dev, "Enabling BATT ID channel failed:%d\n", ret);
> +		return ret;
> +	}
> +
> +	if (chip->batt_id_delay != -EINVAL) {
> +		batt_id_delay =
> +			FIELD_PREP(BATT_ID_SETTLE_MASK, chip->batt_id_delay);
> +		ret = regmap_update_bits(chip->regmap,
> +					 chip->base + RR_ADC_BATT_ID_CFG,
> +					 batt_id_delay, batt_id_delay);
> +		if (ret < 0) {
> +			dev_err(chip->dev,
> +				"BATT_ID settling time config failed:%d\n",
> +				ret);
> +			goto out_disable_batt_id;
> +		}
> +	}
> +
> +	ret = regmap_update_bits(chip->regmap,
> +				 chip->base + RR_ADC_BATT_ID_TRIGGER,
> +				 RR_ADC_TRIGGER_CTL, RR_ADC_TRIGGER_CTL);
> +	if (ret < 0) {
> +		dev_err(chip->dev, "BATT_ID trigger set failed:%d\n", ret);
> +		goto out_disable_batt_id;
> +	}
> +
> +	ret = rradc_read_status_in_cont_mode(chip, chan_id);
> +
> +	/*
> +	 * Reset registers back to default values

/* Reset registers back to default values */

And similar for all other comments that fit on one shortish line.

> +	 */
> +	regmap_update_bits(chip->regmap,
> +				 chip->base + RR_ADC_BATT_ID_TRIGGER,
> +				 RR_ADC_TRIGGER_CTL, 0);
> +
> +out_disable_batt_id:
> +	regmap_update_bits(chip->regmap, chip->base + RR_ADC_BATT_ID_CTRL,
> +				 RR_ADC_BATT_ID_CTRL_CHANNEL_CONV, 0);
> +
> +	return ret;
> +}
> +
> +static int rradc_do_conversion(struct rradc_chip *chip,
> +			       enum rradc_channel_id chan_id, u16 *data)
> +{
> +	const struct rradc_channel *chan = &rradc_chans[chan_id];
> +	const struct iio_chan_spec *iio_chan = &rradc_iio_chans[chan_id];
> +	int ret;
> +	u8 buf[6];
> +
> +	mutex_lock(&chip->lock);
> +
> +	switch (chan_id) {
> +	case RR_ADC_BATT_ID:
> +		ret = rradc_prepare_batt_id_conversion(chip, chan_id, data);
> +		if (ret < 0) {
> +			dev_err(chip->dev, "Battery ID conversion failed:%d\n",
> +				ret);
> +			goto unlock_out;
> +		}
> +		break;
> +
> +	case RR_ADC_USBIN_V:
> +	case RR_ADC_DIE_TEMP:
> +		ret = rradc_read_status_in_cont_mode(chip, chan_id);
> +		if (ret < 0) {
> +			dev_err(chip->dev,
> +				"Error reading in continuous mode:%d\n", ret);
> +			goto unlock_out;
> +		}
> +		break;
> +	case RR_ADC_CHG_HOT_TEMP:
> +	case RR_ADC_CHG_TOO_HOT_TEMP:
> +	case RR_ADC_SKIN_HOT_TEMP:
> +	case RR_ADC_SKIN_TOO_HOT_TEMP:
> +		break;
> +	default:
> +		if (!rradc_is_ready(chip, chan_id)) {
> +			/*
> +			 * Usually this means the channel isn't attached, for example
> +			 * the in_voltage_usbin_v_input channel will not be ready if
> +			 * no USB cable is attached
> +			 */
> +			dev_dbg(chip->dev, "channel '%s' is not ready\n",
> +				iio_chan->extend_name);
> +			ret = -ENODATA;
> +			goto unlock_out;
> +		}
> +		break;
> +	}
> +
> +	ret = rradc_read(chip, chan->lsb, buf, chan->size);
> +	if (ret) {
> +		dev_err(chip->dev, "read data failed\n");
> +		goto unlock_out;
> +	}
> +
> +	/*
> +	 * For the battery ID we read the register for every ID ADC and then
> +	 * see which one is actually connected.
> +	 */
> +	if (chan_id == RR_ADC_BATT_ID) {
> +		u16 batt_id_150 = get_unaligned_le16(buf + 4);
> +		u16 batt_id_15 = get_unaligned_le16(buf + 2);
> +		u16 batt_id_5 = get_unaligned_le16(buf);
> +
> +		if (!batt_id_150 && !batt_id_15 && !batt_id_5) {
> +			dev_err(chip->dev,
> +				"Invalid batt_id values with all zeros\n");
> +			ret = -EINVAL;
> +			goto unlock_out;
> +		}
> +
> +		if (batt_id_150 <= RR_ADC_BATT_ID_RANGE) {
> +			*data = batt_id_150;
> +			chip->batt_id_data = 150;
> +		} else if (batt_id_15 <= RR_ADC_BATT_ID_RANGE) {
> +			*data = batt_id_15;
> +			chip->batt_id_data = 15;
> +		} else {
> +			*data = batt_id_5;
> +			chip->batt_id_data = 5;

This feels like it shouldn't really be in the ADC driver - but rather the
channel data should be used by the battery driver to work out the ID.

> +		}
> +	} else {
> +		/*
> +		 * All of the other channels are either 1 or 2 bytes.
> +		 * We can rely on the second byte being 0 for 1-byte channels.
> +		 */
> +		*data = get_unaligned_le16(buf);
> +	}
> +
> +unlock_out:
> +	mutex_unlock(&chip->lock);
> +
> +	return ret;
> +}
> +
> +static int rradc_read_raw(struct iio_dev *indio_dev,
> +			  struct iio_chan_spec const *chan_spec, int *val,
> +			  int *val2, long mask)
> +{
> +	struct rradc_chip *chip = iio_priv(indio_dev);
> +	const struct rradc_channel *chan;
> +	int ret;
> +	u16 adc_code;
> +
> +	if (chan_spec->address >= RR_ADC_CHAN_MAX) {
> +		dev_err(chip->dev, "Invalid channel index:%ld\n",
> +			chan_spec->address);
> +		return -EINVAL;
> +	}
> +
> +	chan = &rradc_chans[chan_spec->address];
> +	ret = rradc_do_conversion(chip, chan_spec->address, &adc_code);
> +	if (ret < 0)
> +		return ret;
> +
> +	switch (mask) {
> +	case IIO_CHAN_INFO_RAW:
> +		*val = adc_code;
> +		return IIO_VAL_INT;
> +	case IIO_CHAN_INFO_PROCESSED:
> +		chan->scale(chip, adc_code, val);
> +		return IIO_VAL_INT;
> +	default:
> +		return -EINVAL;
> +	}
> +}
> +
> +static const struct iio_info rradc_info = {
> +	.read_raw = &rradc_read_raw,
> +};
> +
> +static const struct rradc_channel rradc_chans[RR_ADC_CHAN_MAX] = {
> +	{
> +		.scale = rradc_post_process_batt_id,
> +		.lsb = RR_ADC_BATT_ID_5_LSB,
> +		.status = RR_ADC_BATT_ID_STS,
> +		.size = 6,
> +		.trigger_addr = RR_ADC_BATT_ID_TRIGGER,
> +		.trigger_mask = BIT(0),
> +	},
> +	{
> +		.scale = rradc_post_process_therm,
> +		.lsb = RR_ADC_BATT_THERM_LSB,
> +		.status = RR_ADC_BATT_THERM_STS,
> +		.size = 2,
> +		.trigger_addr = RR_ADC_BATT_THERM_TRIGGER,
> +	},
> +	{
> +		.scale = rradc_post_process_therm,
> +		.lsb = RR_ADC_SKIN_TEMP_LSB,
> +		.status = RR_ADC_AUX_THERM_STS,
> +		.size = 2,
> +		.trigger_addr = RR_ADC_AUX_THERM_TRIGGER,
> +	},
> +	{
> +		.scale = rradc_post_process_usbin_curr,
> +		.lsb = RR_ADC_USB_IN_I_LSB,
> +		.status = RR_ADC_USB_IN_I_STS,
> +		.size = 2,
> +		.trigger_addr = RR_ADC_USB_IN_I_TRIGGER,
> +	},
> +	{
> +		.scale = rradc_post_process_volt,
> +		.lsb = RR_ADC_USB_IN_V_LSB,
> +		.status = RR_ADC_USB_IN_V_STS,
> +		.size = 2,
> +		.trigger_addr = RR_ADC_USB_IN_V_TRIGGER,
> +		.trigger_mask = BIT(7),
> +	},
> +	{
> +		.scale = rradc_post_process_dcin_curr,
> +		.lsb = RR_ADC_DC_IN_I_LSB,
> +		.status = RR_ADC_DC_IN_I_STS,
> +		.size = 2,
> +		.trigger_addr = RR_ADC_DC_IN_I_TRIGGER,
> +	},
> +	{
> +		.scale = rradc_post_process_volt,
> +		.lsb = RR_ADC_DC_IN_V_LSB,
> +		.status = RR_ADC_DC_IN_V_STS,
> +		.size = 2,
> +		.trigger_addr = RR_ADC_DC_IN_V_TRIGGER,
> +	},
> +	{
> +		.scale = rradc_post_process_die_temp,
> +		.lsb = RR_ADC_PMI_DIE_TEMP_LSB,
> +		.status = RR_ADC_PMI_DIE_TEMP_STS,
> +		.size = 2,
> +		.trigger_addr = RR_ADC_PMI_DIE_TEMP_TRIGGER,
> +		.trigger_mask = RR_ADC_TRIGGER_EVERY_CYCLE,
> +	},
> +	{
> +		.scale = rradc_post_process_chg_temp,
> +		.lsb = RR_ADC_CHARGER_TEMP_LSB,
> +		.status = RR_ADC_CHARGER_TEMP_STS,
> +		.size = 2,
> +		.trigger_addr = RR_ADC_CHARGER_TEMP_TRIGGER,
> +	},
> +	{
> +		.scale = rradc_post_process_gpio,
> +		.lsb = RR_ADC_GPIO_LSB,
> +		.status = RR_ADC_GPIO_STS,
> +		.size = 2,
> +		.trigger_addr = RR_ADC_GPIO_TRIGGER,
> +	},
> +	{
> +		.scale = rradc_post_process_chg_temp_hot,
> +		.lsb = RR_ADC_CHARGER_HOT,
> +		.status = RR_ADC_CHARGER_TEMP_STS,
> +		.size = 1,
> +		.trigger_addr = RR_ADC_CHARGER_TEMP_TRIGGER,
> +	},
> +	{
> +		.scale = rradc_post_process_chg_temp_hot,
> +		.lsb = RR_ADC_CHARGER_TOO_HOT,
> +		.status = RR_ADC_CHARGER_TEMP_STS,
> +		.size = 1,
> +		.trigger_addr = RR_ADC_CHARGER_TEMP_TRIGGER,
> +	},
> +	{
> +		.scale = rradc_post_process_skin_temp_hot,
> +		.lsb = RR_ADC_SKIN_HOT,
> +		.status = RR_ADC_AUX_THERM_STS,
> +		.size = 1,
> +		.trigger_addr = RR_ADC_AUX_THERM_TRIGGER,
> +	},
> +	{
> +		.scale = rradc_post_process_skin_temp_hot,
> +		.lsb = RR_ADC_SKIN_TOO_HOT,
> +		.status = RR_ADC_AUX_THERM_STS,
> +		.size = 1,
> +		.trigger_addr = RR_ADC_AUX_THERM_TRIGGER,
> +	},
> +};
> +
> +static const struct iio_chan_spec rradc_iio_chans[RR_ADC_CHAN_MAX] = {
> +	{
> +		.extend_name = "batt_id",

We recently introduced channel labels to try and avoid the need for
extend_name.  The problem with extend_name is that generic software then
has trouble parsing the resulting sysfs files as they can have very
freeform naming.  Moving it to label makes that much easier.  Note that
there is code to give a default label of extend_name to work around
this problem for older drivers.

> +		.type = IIO_RESISTANCE,
> +		.info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED),
> +		.address = RR_ADC_BATT_ID,
> +	},
> +	{
> +		.extend_name = "batt_therm",
> +		.type = IIO_TEMP,
> +		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
> +		.address = RR_ADC_BATT_THERM,

Channel should be set for these and they should be indexed.
That will be needed when you move away from extend_name and is needed
for anything like events if the device supports such threshold detection
features.  Preference for adc channels to always have an index these days.

> +	},
> +	{
> +		.extend_name = "skin_temp",
> +		.type = IIO_TEMP,
> +		.info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED)|
> +			     BIT(IIO_CHAN_INFO_RAW),

You need a very strong reason to provide both PROCESSED and RAW for
a channel.
1) Historical reason - so typically _RAW was provided first but the
   transform to _PROCESSED is non linear and so when it was added
   we had to keep _RAW to avoid ABI breakage.
2) Very odd corner cases where there are threshold settings and
   an annoyingly one way transformation maths to get to the
   _PROCESSED value.
3) Something else for which you need to make an argument in a comment
   here...

> +		.address = RR_ADC_SKIN_TEMP,
> +	},
> +	{
> +		.extend_name = "usbin_i",
> +		.type = IIO_CURRENT,
> +		.info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED),

> +		.address = RR_ADC_USBIN_I,
> +	},
> +	{
> +		.extend_name = "usbin_v",
> +		.type = IIO_VOLTAGE,
> +		.info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED),
> +		.address = RR_ADC_USBIN_V,
> +	},
> +	{
> +		.extend_name = "dcin_i",
> +		.type = IIO_CURRENT,
> +		.info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED),
> +		.address = RR_ADC_DCIN_I,
> +	},
> +	{
> +		.extend_name = "dcin_v",
> +		.type = IIO_VOLTAGE,
> +		.info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED),
> +		.address = RR_ADC_DCIN_V,
> +	},
> +	{
> +		.extend_name = "die_temp",
> +		.type = IIO_TEMP,
> +		.info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED)|
> +			     BIT(IIO_CHAN_INFO_RAW),
> +		.address = RR_ADC_DIE_TEMP,
> +	},
> +	{
> +		.extend_name = "chg_temp",
> +		.type = IIO_TEMP,
> +		.info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED)|
> +			     BIT(IIO_CHAN_INFO_RAW),
> +		.address = RR_ADC_CHG_TEMP,
> +	},
> +	{
> +		.extend_name = "gpio",
> +		.type = IIO_VOLTAGE,
> +		.info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED)|
> +			     BIT(IIO_CHAN_INFO_RAW),
> +		.address = RR_ADC_GPIO,
> +	},
> +	{
> +		.extend_name = "chg_temp_hot",
> +		.type = IIO_TEMP,
> +		.info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED)|
> +			     BIT(IIO_CHAN_INFO_RAW),
> +		.address = RR_ADC_CHG_HOT_TEMP,
> +	},
> +	{
> +		.extend_name = "chg_temp_too_hot",
> +		.type = IIO_TEMP,
> +		.info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED)|
> +			     BIT(IIO_CHAN_INFO_RAW),
> +		.address = RR_ADC_CHG_TOO_HOT_TEMP,
> +	},
> +	{
> +		.extend_name = "skin_temp_hot",
> +		.type = IIO_TEMP,
> +		.info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED)|
> +			     BIT(IIO_CHAN_INFO_RAW),
> +		.address = RR_ADC_SKIN_TEMP,
> +	},
> +	{
> +		.extend_name = "skin_temp_too_hot",
> +		.type = IIO_TEMP,
> +		.info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED)|
> +			     BIT(IIO_CHAN_INFO_RAW),
> +		.address = RR_ADC_SKIN_TEMP,
> +	},
> +};
> +
> +static int rradc_probe(struct platform_device *pdev)
> +{
> +	struct device *dev = &pdev->dev;
> +	struct iio_dev *indio_dev;
> +	struct rradc_chip *chip;
> +	int ret, i;
> +
> +	indio_dev = devm_iio_device_alloc(dev, sizeof(*chip));
> +	if (!indio_dev)
> +		return -ENOMEM;
> +
> +	chip = iio_priv(indio_dev);
> +	chip->regmap = dev_get_regmap(pdev->dev.parent, NULL);
> +	if (!chip->regmap) {
> +		dev_err(dev, "Couldn't get parent's regmap\n");
> +		return -EINVAL;
> +	}
> +
> +	chip->dev = dev;
> +	mutex_init(&chip->lock);
> +
> +	ret = device_property_read_u32(dev, "reg", &chip->base);
> +	if (ret < 0) {
> +		dev_err(chip->dev, "Couldn't find reg address, ret = %d\n",
> +			ret);
> +		return ret;
> +	}
> +
> +	chip->batt_id_delay = -EINVAL;

Is there an effective default for chip->batt_id_delay?
It seems like you just leave it set to whatever it was at boot if this
isn't specified.  Is this likely to be firmware controlled?  If not
I'd suggest putting a default in the dt-binding and using that here
rather than just bypassing the logic to set it.  That way we get
less special case code, making testing etc easier.

If the aim is to allow firmware to have set it, perhaps read back
what is set then let the rest of the code set it to the existing value.
Again, the advantage is simplicity in most code paths.

> +	ret = device_property_read_u32(dev, "qcom,batt-id-delay-ms",
> +				       &chip->batt_id_delay);
> +	if (!ret) {
> +		for (i = 0; i < RRADC_BATT_ID_DELAY_MAX; i++) {
> +			if (chip->batt_id_delay == batt_id_delays[i])
> +				break;
> +		}
> +		if (i == RRADC_BATT_ID_DELAY_MAX)
> +			chip->batt_id_delay = -EINVAL;
> +	}
> +
> +	/* Get the PMIC revision ID, we need to handle some varying coefficients */
> +	chip->pmic = (struct qcom_spmi_pmic *)spmi_device_get_drvdata(
> +		to_spmi_device(pdev->dev.parent));
> +	qcom_pmic_print_info(chip->dev, chip->pmic);
> +
> +	indio_dev->name = pdev->name;

This should be the part number - is that the case with pdev->name in this case?

> +	indio_dev->modes = INDIO_DIRECT_MODE;
> +	indio_dev->info = &rradc_info;
> +	indio_dev->channels = rradc_iio_chans;
> +	indio_dev->num_channels = RR_ADC_CHAN_MAX;
Preference for ARRAY_SIZE(rradc_iio_chans) because it saves a reviewer checking
these two sizes match.

> +
> +	return devm_iio_device_register(dev, indio_dev);
> +}
> +

Thanks,

Jonathan