iio: adc: Add driver for Marvell 88PM886 PMIC ADC

Marvell's 88PM886 PMIC has a so-called General Purpose ADC used for
monitoring various system voltages and temperatures. Add the relevant
register definitions to the MFD header and a driver for the ADC.

Acked-by: Karel Balej <[e-mail]> # for the PMIC
Signed-off-by: Duje Mihanović <[e-mail]>
Signed-off-by: Jonathan Cameron <[e-mail]>

MAINTAINERS

···
 F:	drivers/rtc/rtc-88pm886.c
 F:	include/linux/mfd/88pm886.h
 
+MARVELL 88PM886 PMIC GPADC DRIVER
+M:	Duje Mihanović <[e-mail]>
+S:	Maintained
+F:	drivers/iio/adc/88pm886-gpadc.c
+
 MARVELL ARMADA 3700 PHY DRIVERS
 M:	Miquel Raynal <[e-mail]>
 S:	Maintained

drivers/iio/adc/88pm886-gpadc.c

···
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright 2025, Duje Mihanović <[e-mail]>
+ */
+
+#include <linux/bits.h>
+#include <linux/bug.h>
+#include <linux/delay.h>
+#include <linux/device.h>
+#include <linux/err.h>
+#include <linux/i2c.h>
+#include <linux/math.h>
+#include <linux/mod_devicetable.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/pm_runtime.h>
+#include <linux/regmap.h>
+#include <linux/types.h>
+#include <linux/units.h>
+
+#include <asm/byteorder.h>
+
+#include <linux/iio/iio.h>
+#include <linux/iio/types.h>
+
+#include <linux/mfd/88pm886.h>
+
+struct pm886_gpadc {
+	struct regmap *map;
+};
+
+enum pm886_gpadc_channel {
+	VSC_CHAN,
+	VCHG_PWR_CHAN,
+	VCF_OUT_CHAN,
+	VBAT_CHAN,
+	VBAT_SLP_CHAN,
+	VBUS_CHAN,
+
+	GPADC0_CHAN,
+	GPADC1_CHAN,
+	GPADC2_CHAN,
+	GPADC3_CHAN,
+
+	GND_DET1_CHAN,
+	GND_DET2_CHAN,
+	MIC_DET_CHAN,
+
+	TINT_CHAN,
+};
+
+static const int pm886_gpadc_regs[] = {
+	[VSC_CHAN] = PM886_REG_GPADC_VSC,
+	[VCHG_PWR_CHAN] = PM886_REG_GPADC_VCHG_PWR,
+	[VCF_OUT_CHAN] = PM886_REG_GPADC_VCF_OUT,
+	[VBAT_CHAN] = PM886_REG_GPADC_VBAT,
+	[VBAT_SLP_CHAN] = PM886_REG_GPADC_VBAT_SLP,
+	[VBUS_CHAN] = PM886_REG_GPADC_VBUS,
+
+	[GPADC0_CHAN] = PM886_REG_GPADC_GPADC0,
+	[GPADC1_CHAN] = PM886_REG_GPADC_GPADC1,
+	[GPADC2_CHAN] = PM886_REG_GPADC_GPADC2,
+	[GPADC3_CHAN] = PM886_REG_GPADC_GPADC3,
+
+	[GND_DET1_CHAN] = PM886_REG_GPADC_GND_DET1,
+	[GND_DET2_CHAN] = PM886_REG_GPADC_GND_DET2,
+	[MIC_DET_CHAN] = PM886_REG_GPADC_MIC_DET,
+
+	[TINT_CHAN] = PM886_REG_GPADC_TINT,
+};
+
+#define ADC_CHANNEL_VOLTAGE(index, lsb, name)		\
+{							\
+	.type = IIO_VOLTAGE,				\
+	.indexed = 1,					\
+	.channel = index,				\
+	.address = lsb,					\
+	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |	\
+			      BIT(IIO_CHAN_INFO_SCALE),	\
+	.datasheet_name = name,				\
+}
+
+#define ADC_CHANNEL_RESISTANCE(index, lsb, name)		\
+{								\
+	.type = IIO_RESISTANCE,					\
+	.indexed = 1,						\
+	.channel = index,					\
+	.address = lsb,						\
+	.info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED),	\
+	.datasheet_name = name,					\
+}
+
+#define ADC_CHANNEL_TEMPERATURE(index, lsb, name)		\
+{								\
+	.type = IIO_TEMP,					\
+	.indexed = 1,						\
+	.channel = index,					\
+	.address = lsb,						\
+	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |		\
+			      BIT(IIO_CHAN_INFO_SCALE) |	\
+			      BIT(IIO_CHAN_INFO_OFFSET),	\
+	.datasheet_name = name,					\
+}
+
+static const struct iio_chan_spec pm886_gpadc_channels[] = {
+	ADC_CHANNEL_VOLTAGE(VSC_CHAN, 1367, "vsc"),
+	ADC_CHANNEL_VOLTAGE(VCHG_PWR_CHAN, 1709, "vchg_pwr"),
+	ADC_CHANNEL_VOLTAGE(VCF_OUT_CHAN, 1367, "vcf_out"),
+	ADC_CHANNEL_VOLTAGE(VBAT_CHAN, 1367, "vbat"),
+	ADC_CHANNEL_VOLTAGE(VBAT_SLP_CHAN, 1367, "vbat_slp"),
+	ADC_CHANNEL_VOLTAGE(VBUS_CHAN, 1709, "vbus"),
+
+	ADC_CHANNEL_RESISTANCE(GPADC0_CHAN, 342, "gpadc0"),
+	ADC_CHANNEL_RESISTANCE(GPADC1_CHAN, 342, "gpadc1"),
+	ADC_CHANNEL_RESISTANCE(GPADC2_CHAN, 342, "gpadc2"),
+	ADC_CHANNEL_RESISTANCE(GPADC3_CHAN, 342, "gpadc3"),
+
+	ADC_CHANNEL_VOLTAGE(GND_DET1_CHAN, 342, "gnddet1"),
+	ADC_CHANNEL_VOLTAGE(GND_DET2_CHAN, 342, "gnddet2"),
+	ADC_CHANNEL_VOLTAGE(MIC_DET_CHAN, 1367, "mic_det"),
+
+	ADC_CHANNEL_TEMPERATURE(TINT_CHAN, 104, "tint"),
+};
+
+static const struct regmap_config pm886_gpadc_regmap_config = {
+	.reg_bits = 8,
+	.val_bits = 8,
+	.max_register = PM886_GPADC_MAX_REGISTER,
+};
+
+static int gpadc_get_raw(struct iio_dev *iio, enum pm886_gpadc_channel chan)
+{
+	struct pm886_gpadc *gpadc = iio_priv(iio);
+	__be16 buf;
+	int ret;
+
+	ret = regmap_bulk_read(gpadc->map, pm886_gpadc_regs[chan], &buf, sizeof(buf));
+	if (ret)
+		return ret;
+
+	return be16_to_cpu(buf) >> 4;
+}
+
+static int
+gpadc_set_bias(struct pm886_gpadc *gpadc, enum pm886_gpadc_channel chan, bool on)
+{
+	unsigned int gpadc_num = chan - GPADC0_CHAN;
+	unsigned int bits = BIT(gpadc_num + 4) | BIT(gpadc_num);
+
+	return regmap_assign_bits(gpadc->map, PM886_REG_GPADC_CONFIG(0x14), bits, on);
+}
+
+static int
+gpadc_find_bias_current(struct iio_dev *iio, struct iio_chan_spec const *chan,
+			unsigned int *raw_uV, unsigned int *raw_uA)
+{
+	struct pm886_gpadc *gpadc = iio_priv(iio);
+	unsigned int gpadc_num = chan->channel - GPADC0_CHAN;
+	unsigned int reg = PM886_REG_GPADC_CONFIG(0xb + gpadc_num);
+	unsigned long lsb = chan->address;
+	int ret;
+
+	for (unsigned int i = 0; i < PM886_GPADC_BIAS_LEVELS; i++) {
+		ret = regmap_update_bits(gpadc->map, reg, GENMASK(3, 0), i);
+		if (ret)
+			return ret;
+
+		/* Wait for the new bias level to apply. */
+		fsleep(5 * USEC_PER_MSEC);
+
+		*raw_uA = PM886_GPADC_INDEX_TO_BIAS_uA(i);
+		*raw_uV = gpadc_get_raw(iio, chan->channel) * lsb;
+
+		/*
+		 * Vendor kernel errors out above 1.25 V, but testing shows
+		 * that the resistance of the battery detection channel (GPADC2
+		 * on coreprimevelte) reaches about 1.4 MΩ when the battery is
+		 * removed, which can't be measured with such a low upper
+		 * limit. Therefore, to be able to detect the battery without
+		 * ugly externs as used in the vendor fuel gauge driver,
+		 * increase this limit a bit.
+		 */
+		if (WARN_ON(*raw_uV > 1500 * (MICRO / MILLI)))
+			return -EIO;
+
+		/*
+		 * Vendor kernel errors out under 300 mV, but for the same
+		 * reason as above (except the channel hovers around 3.5 kΩ
+		 * with battery present) reduce this limit.
+		 */
+		if (*raw_uV < 200 * (MICRO / MILLI)) {
+			dev_dbg(&iio->dev, "bad bias for chan %d: %d uA @ %d uV\n",
+				chan->channel, *raw_uA, *raw_uV);
+			continue;
+		}
+
+		dev_dbg(&iio->dev, "good bias for chan %d: %d uA @ %d uV\n",
+			chan->channel, *raw_uA, *raw_uV);
+		return 0;
+	}
+
+	dev_err(&iio->dev, "failed to find good bias for chan %d\n", chan->channel);
+	return -EINVAL;
+}
+
+static int
+gpadc_get_resistance_ohm(struct iio_dev *iio, struct iio_chan_spec const *chan)
+{
+	struct pm886_gpadc *gpadc = iio_priv(iio);
+	unsigned int raw_uV, raw_uA;
+	int ret;
+
+	ret = gpadc_set_bias(gpadc, chan->channel, true);
+	if (ret)
+		goto out;
+
+	ret = gpadc_find_bias_current(iio, chan, &raw_uV, &raw_uA);
+	if (ret)
+		goto out;
+
+	ret = DIV_ROUND_CLOSEST(raw_uV, raw_uA);
+out:
+	gpadc_set_bias(gpadc, chan->channel, false);
+	return ret;
+}
+
+static int
+__pm886_gpadc_read_raw(struct iio_dev *iio, struct iio_chan_spec const *chan,
+		       int *val, int *val2, long mask)
+{
+	unsigned long lsb = chan->address;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW:
+		*val = gpadc_get_raw(iio, chan->channel);
+		if (*val < 0)
+			return *val;
+
+		return IIO_VAL_INT;
+	case IIO_CHAN_INFO_SCALE:
+		*val = lsb;
+
+		if (chan->type == IIO_VOLTAGE) {
+			*val2 = MILLI;
+			return IIO_VAL_FRACTIONAL;
+		} else {
+			return IIO_VAL_INT;
+		}
+	case IIO_CHAN_INFO_OFFSET:
+		/* Raw value is 104 millikelvin/LSB, convert it to 104 millicelsius/LSB */
+		*val = ABSOLUTE_ZERO_MILLICELSIUS;
+		*val2 = lsb;
+		return IIO_VAL_FRACTIONAL;
+	case IIO_CHAN_INFO_PROCESSED:
+		*val = gpadc_get_resistance_ohm(iio, chan);
+		if (*val < 0)
+			return *val;
+
+		return IIO_VAL_INT;
+	default:
+		return -EINVAL;
+	}
+}
+
+static int pm886_gpadc_read_raw(struct iio_dev *iio, struct iio_chan_spec const *chan,
+				int *val, int *val2, long mask)
+{
+	struct device *dev = iio->dev.parent;
+	int ret;
+
+	ret = pm_runtime_resume_and_get(dev);
+	if (ret)
+		return ret;
+
+	ret = __pm886_gpadc_read_raw(iio, chan, val, val2, mask);
+
+	pm_runtime_put_autosuspend(dev);
+	return ret;
+}
+
+static int pm886_gpadc_hw_enable(struct regmap *map)
+{
+	const u8 config[] = {
+		PM886_GPADC_CONFIG1_EN_ALL,
+		PM886_GPADC_CONFIG2_EN_ALL,
+		PM886_GPADC_GND_DET2_EN,
+	};
+	int ret;
+
+	/* Enable the ADC block. */
+	ret = regmap_set_bits(map, PM886_REG_GPADC_CONFIG(0x6), BIT(0));
+	if (ret)
+		return ret;
+
+	/* Enable all channels. */
+	return regmap_bulk_write(map, PM886_REG_GPADC_CONFIG(0x1), config, ARRAY_SIZE(config));
+}
+
+static int pm886_gpadc_hw_disable(struct regmap *map)
+{
+	return regmap_clear_bits(map, PM886_REG_GPADC_CONFIG(0x6), BIT(0));
+}
+
+static const struct iio_info pm886_gpadc_iio_info = {
+	.read_raw = pm886_gpadc_read_raw,
+};
+
+static int pm886_gpadc_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct pm886_chip *chip = dev_get_drvdata(dev->parent);
+	struct i2c_client *client = chip->client;
+	struct pm886_gpadc *gpadc;
+	struct i2c_client *page;
+	struct iio_dev *iio;
+	int ret;
+
+	iio = devm_iio_device_alloc(dev, sizeof(*gpadc));
+	if (!iio)
+		return -ENOMEM;
+
+	gpadc = iio_priv(iio);
+	dev_set_drvdata(dev, iio);
+
+	page = devm_i2c_new_dummy_device(dev, client->adapter,
+					 client->addr + PM886_PAGE_OFFSET_GPADC);
+	if (IS_ERR(page))
+		return dev_err_probe(dev, PTR_ERR(page), "Failed to initialize GPADC page\n");
+
+	gpadc->map = devm_regmap_init_i2c(page, &pm886_gpadc_regmap_config);
+	if (IS_ERR(gpadc->map))
+		return dev_err_probe(dev, PTR_ERR(gpadc->map),
+				     "Failed to initialize GPADC regmap\n");
+
+	iio->name = "88pm886-gpadc";
+	iio->modes = INDIO_DIRECT_MODE;
+	iio->info = &pm886_gpadc_iio_info;
+	iio->channels = pm886_gpadc_channels;
+	iio->num_channels = ARRAY_SIZE(pm886_gpadc_channels);
+	device_set_node(&iio->dev, dev_fwnode(dev->parent));
+
+	ret = devm_pm_runtime_enable(dev);
+	if (ret)
+		return dev_err_probe(dev, ret, "Failed to enable runtime PM\n");
+
+	pm_runtime_set_autosuspend_delay(dev, 50);
+	pm_runtime_use_autosuspend(dev);
+	ret = devm_iio_device_register(dev, iio);
+	if (ret)
+		return dev_err_probe(dev, ret, "Failed to register ADC\n");
+
+	return 0;
+}
+
+static int pm886_gpadc_runtime_resume(struct device *dev)
+{
+	struct iio_dev *iio = dev_get_drvdata(dev);
+	struct pm886_gpadc *gpadc = iio_priv(iio);
+
+	return pm886_gpadc_hw_enable(gpadc->map);
+}
+
+static int pm886_gpadc_runtime_suspend(struct device *dev)
+{
+	struct iio_dev *iio = dev_get_drvdata(dev);
+	struct pm886_gpadc *gpadc = iio_priv(iio);
+
+	return pm886_gpadc_hw_disable(gpadc->map);
+}
+
+static DEFINE_RUNTIME_DEV_PM_OPS(pm886_gpadc_pm_ops,
+				 pm886_gpadc_runtime_suspend,
+				 pm886_gpadc_runtime_resume, NULL);
+
+static const struct platform_device_id pm886_gpadc_id[] = {
+	{ "88pm886-gpadc" },
+	{ }
+};
+MODULE_DEVICE_TABLE(platform, pm886_gpadc_id);
+
+static struct platform_driver pm886_gpadc_driver = {
+	.driver = {
+		.name = "88pm886-gpadc",
+		.pm = pm_ptr(&pm886_gpadc_pm_ops),
+	},
+	.probe = pm886_gpadc_probe,
+	.id_table = pm886_gpadc_id,
+};
+module_platform_driver(pm886_gpadc_driver);
+
+MODULE_AUTHOR("Duje Mihanović <[e-mail]>");
+MODULE_DESCRIPTION("Marvell 88PM886 GPADC driver");
+MODULE_LICENSE("GPL");

drivers/iio/adc/Kconfig

···
 config IIO_ADC_HELPER
 	tristate
 
+config 88PM886_GPADC
+	tristate "Marvell 88PM886 GPADC driver"
+	depends on MFD_88PM886_PMIC
+	default MFD_88PM886_PMIC
+	help
+	  Say Y here to enable support for the GPADC (General Purpose ADC)
+	  found on the Marvell 88PM886 PMIC. The GPADC measures various
+	  internal voltages and temperatures, including (but not limited to)
+	  system, battery and USB Vbus.
+
+	  To compile this driver as a module, choose M here: the module will be
+	  called 88pm886-gpadc.
+
 config AB8500_GPADC
 	bool "ST-Ericsson AB8500 GPADC driver"
 	depends on AB8500_CORE && REGULATOR_AB8500

drivers/iio/adc/Makefile

···
 obj-$(CONFIG_IIO_ADC_HELPER) += industrialio-adc.o
 
 # When adding new entries keep the list in alphabetical order
+obj-$(CONFIG_88PM886_GPADC) += 88pm886-gpadc.o
 obj-$(CONFIG_AB8500_GPADC) += ab8500-gpadc.o
 obj-$(CONFIG_AD_SIGMA_DELTA) += ad_sigma_delta.o
 obj-$(CONFIG_AD4000) += ad4000.o

include/linux/mfd/88pm886.h

···
 #define PM886_IRQ_ONKEY			0
 
 #define PM886_PAGE_OFFSET_REGULATORS	1
+#define PM886_PAGE_OFFSET_GPADC		2
 
 #define PM886_REG_ID			0x00
 
···
 
 #define PM886_LDO_VSEL_MASK		0x0f
 #define PM886_BUCK_VSEL_MASK		0x7f
+
+/* GPADC enable/disable registers */
+#define PM886_REG_GPADC_CONFIG(n)	(n)
+
+#define PM886_GPADC_VSC_EN		BIT(0)
+#define PM886_GPADC_VBAT_EN		BIT(1)
+#define PM886_GPADC_GNDDET1_EN		BIT(3)
+#define PM886_GPADC_VBUS_EN		BIT(4)
+#define PM886_GPADC_VCHG_PWR_EN		BIT(5)
+#define PM886_GPADC_VCF_OUT_EN		BIT(6)
+#define PM886_GPADC_CONFIG1_EN_ALL	\
+	(PM886_GPADC_VSC_EN |		\
+	 PM886_GPADC_VBAT_EN |		\
+	 PM886_GPADC_GNDDET1_EN |	\
+	 PM886_GPADC_VBUS_EN |		\
+	 PM886_GPADC_VCHG_PWR_EN |	\
+	 PM886_GPADC_VCF_OUT_EN)
+
+#define PM886_GPADC_TINT_EN		BIT(0)
+#define PM886_GPADC_PMODE_EN		BIT(1)
+#define PM886_GPADC_GPADC0_EN		BIT(2)
+#define PM886_GPADC_GPADC1_EN		BIT(3)
+#define PM886_GPADC_GPADC2_EN		BIT(4)
+#define PM886_GPADC_GPADC3_EN		BIT(5)
+#define PM886_GPADC_MIC_DET_EN		BIT(6)
+#define PM886_GPADC_CONFIG2_EN_ALL	\
+	(PM886_GPADC_TINT_EN |		\
+	 PM886_GPADC_GPADC0_EN |	\
+	 PM886_GPADC_GPADC1_EN |	\
+	 PM886_GPADC_GPADC2_EN |	\
+	 PM886_GPADC_GPADC3_EN |	\
+	 PM886_GPADC_MIC_DET_EN)
+
+/* No CONFIG3_EN_ALL because this is the only bit there. */
+#define PM886_GPADC_GND_DET2_EN		BIT(0)
+
+/* GPADC channel registers */
+#define PM886_REG_GPADC_VSC		0x40
+#define PM886_REG_GPADC_VCHG_PWR	0x4c
+#define PM886_REG_GPADC_VCF_OUT		0x4e
+#define PM886_REG_GPADC_TINT		0x50
+#define PM886_REG_GPADC_GPADC0		0x54
+#define PM886_REG_GPADC_GPADC1		0x56
+#define PM886_REG_GPADC_GPADC2		0x58
+#define PM886_REG_GPADC_VBAT		0xa0
+#define PM886_REG_GPADC_GND_DET1	0xa4
+#define PM886_REG_GPADC_GND_DET2	0xa6
+#define PM886_REG_GPADC_VBUS		0xa8
+#define PM886_REG_GPADC_GPADC3		0xaa
+#define PM886_REG_GPADC_MIC_DET		0xac
+#define PM886_REG_GPADC_VBAT_SLP	0xb0
+
+/* VBAT_SLP is the last register and is 2 bytes wide like other channels. */
+#define PM886_GPADC_MAX_REGISTER	(PM886_REG_GPADC_VBAT_SLP + 1)
+
+#define PM886_GPADC_BIAS_LEVELS		16
+#define PM886_GPADC_INDEX_TO_BIAS_uA(i)	(1 + (i) * 5)
 
 struct pm886_chip {
 	struct i2c_client *client;