iio: adc: add a driver for Qualcomm PM8xxx HK/XOADC

The Qualcomm PM8xxx PMICs contain a simpler ADC than its
successors (already in the kernel as qcom-spmi-vadc.c):
the HK/XO ADC (Housekeeping/Chrystal oscillator ADC).

As far as I can understand this is equal to the PMICs
using SSBI transport and encompass PM8018, PM8038,
PM8058, and PM8921, so this is shortly named PM8xxx.

This ADC monitors a bunch of on-board voltages and the die
temperature of the PMIC itself, but it can also be routed
to convert a few external MPPs (multi-purpose pins). On
the APQ8060 DragonBoard this feature is used to let this
ADC convert an analog ALS (Ambient Light Sensor) voltage
signal from a Capella CM3605 ALS into a LUX value.

Developed and tested with APQ8060 DragonBoard based on
Ivan's driver and Rama Krishna's patches. The SPMI VADC
driver is quite different, but share enough minor
functionality that I have split out to the common file
in a previous patch.

Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-arm-msm@vger.kernel.org
Cc: Ivan T. Ivanov <iivanov.xz@gmail.com>
Cc: Andy Gross <andy.gross@linaro.org>
Cc: Bjorn Andersson <bjorn.andersson@linaro.org>
Cc: Stephen Boyd <sboyd@codeaurora.org>
Cc: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Cc: Rama Krishna Phani A <rphani@codeaurora.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

3 files changed, 1048 insertions, 0 deletions

diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
index d8ad694b4709..385fb732dade 100644
--- a/drivers/iio/adc/Kconfig
+++ b/drivers/iio/adc/Kconfig
@@ -499,6 +499,17 @@ config PALMAS_GPADC
 config QCOM_VADC_COMMON
 	tristate
 
+config QCOM_PM8XXX_XOADC
+	tristate "Qualcomm SSBI PM8xxx PMIC XOADCs"
+	depends on MFD_PM8XXX
+	select QCOM_VADC_COMMON
+	help
+	  ADC driver for the XOADC portions of the Qualcomm PM8xxx PMICs
+	  using SSBI transport: PM8018, PM8038, PM8058, PM8921.
+
+	  To compile this driver as a module, choose M here: the module
+	  will be called qcom-pm8xxx-xoadc.
+
 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 50fb66b47f7e..78a7fd84cc59 100644
--- a/drivers/iio/adc/Makefile
+++ b/drivers/iio/adc/Makefile
@@ -50,6 +50,7 @@ obj-$(CONFIG_PALMAS_GPADC) += palmas_gpadc.o
 obj-$(CONFIG_QCOM_SPMI_IADC) += qcom-spmi-iadc.o
 obj-$(CONFIG_QCOM_VADC_COMMON) += qcom-vadc-common.o
 obj-$(CONFIG_QCOM_SPMI_VADC) += qcom-spmi-vadc.o
+obj-$(CONFIG_QCOM_PM8XXX_XOADC) += qcom-pm8xxx-xoadc.o
 obj-$(CONFIG_RCAR_GYRO_ADC) += rcar-gyroadc.o
 obj-$(CONFIG_ROCKCHIP_SARADC) += rockchip_saradc.o
 obj-$(CONFIG_SPEAR_ADC) += spear_adc.o
diff --git a/drivers/iio/adc/qcom-pm8xxx-xoadc.c b/drivers/iio/adc/qcom-pm8xxx-xoadc.c
new file mode 100644
index 000000000000..cea8f1fb444a
--- /dev/null
+++ b/drivers/iio/adc/qcom-pm8xxx-xoadc.c
@@ -0,0 +1,1036 @@
+/*
+ * Qualcomm PM8xxx PMIC XOADC driver
+ *
+ * These ADCs are known as HK/XO (house keeping / chrystal oscillator)
+ * "XO" in "XOADC" means Chrystal Oscillator. It's a bunch of
+ * specific-purpose and general purpose ADC converters and channels.
+ *
+ * Copyright (C) 2017 Linaro Ltd.
+ * Author: Linus Walleij <linus.walleij@linaro.org>
+ */
+
+#include <linux/iio/iio.h>
+#include <linux/iio/sysfs.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/of_device.h>
+#include <linux/platform_device.h>
+#include <linux/regmap.h>
+#include <linux/init.h>
+#include <linux/interrupt.h>
+#include <linux/regulator/consumer.h>
+
+#include "qcom-vadc-common.h"
+
+/*
+ * Definitions for the "user processor" registers lifted from the v3.4
+ * Qualcomm tree. Their kernel has two out-of-tree drivers for the ADC:
+ * drivers/misc/pmic8058-xoadc.c
+ * drivers/hwmon/pm8xxx-adc.c
+ * None of them contain any complete register specification, so this is
+ * a best effort of combining the information.
+ */
+
+/* These appear to be "battery monitor" registers */
+#define ADC_ARB_BTM_CNTRL1			0x17e
+#define ADC_ARB_BTM_CNTRL1_EN_BTM		BIT(0)
+#define ADC_ARB_BTM_CNTRL1_SEL_OP_MODE		BIT(1)
+#define ADC_ARB_BTM_CNTRL1_MEAS_INTERVAL1	BIT(2)
+#define ADC_ARB_BTM_CNTRL1_MEAS_INTERVAL2	BIT(3)
+#define ADC_ARB_BTM_CNTRL1_MEAS_INTERVAL3	BIT(4)
+#define ADC_ARB_BTM_CNTRL1_MEAS_INTERVAL4	BIT(5)
+#define ADC_ARB_BTM_CNTRL1_EOC			BIT(6)
+#define ADC_ARB_BTM_CNTRL1_REQ			BIT(7)
+
+#define ADC_ARB_BTM_AMUX_CNTRL			0x17f
+#define ADC_ARB_BTM_ANA_PARAM			0x180
+#define ADC_ARB_BTM_DIG_PARAM			0x181
+#define ADC_ARB_BTM_RSV				0x182
+#define ADC_ARB_BTM_DATA1			0x183
+#define ADC_ARB_BTM_DATA0			0x184
+#define ADC_ARB_BTM_BAT_COOL_THR1		0x185
+#define ADC_ARB_BTM_BAT_COOL_THR0		0x186
+#define ADC_ARB_BTM_BAT_WARM_THR1		0x187
+#define ADC_ARB_BTM_BAT_WARM_THR0		0x188
+#define ADC_ARB_BTM_CNTRL2			0x18c
+
+/* Proper ADC registers */
+
+#define ADC_ARB_USRP_CNTRL			0x197
+#define ADC_ARB_USRP_CNTRL_EN_ARB		BIT(0)
+#define ADC_ARB_USRP_CNTRL_RSV1			BIT(1)
+#define ADC_ARB_USRP_CNTRL_RSV2			BIT(2)
+#define ADC_ARB_USRP_CNTRL_RSV3			BIT(3)
+#define ADC_ARB_USRP_CNTRL_RSV4			BIT(4)
+#define ADC_ARB_USRP_CNTRL_RSV5			BIT(5)
+#define ADC_ARB_USRP_CNTRL_EOC			BIT(6)
+#define ADC_ARB_USRP_CNTRL_REQ			BIT(7)
+
+#define ADC_ARB_USRP_AMUX_CNTRL			0x198
+/*
+ * The channel mask includes the bits selecting channel mux and prescaler
+ * on PM8058, or channel mux and premux on PM8921.
+ */
+#define ADC_ARB_USRP_AMUX_CNTRL_CHAN_MASK	0xfc
+#define ADC_ARB_USRP_AMUX_CNTRL_RSV0		BIT(0)
+#define ADC_ARB_USRP_AMUX_CNTRL_RSV1		BIT(1)
+/* On PM8058 this is prescaling, on PM8921 this is premux */
+#define ADC_ARB_USRP_AMUX_CNTRL_PRESCALEMUX0	BIT(2)
+#define ADC_ARB_USRP_AMUX_CNTRL_PRESCALEMUX1	BIT(3)
+#define ADC_ARB_USRP_AMUX_CNTRL_SEL0		BIT(4)
+#define ADC_ARB_USRP_AMUX_CNTRL_SEL1		BIT(5)
+#define ADC_ARB_USRP_AMUX_CNTRL_SEL2		BIT(6)
+#define ADC_ARB_USRP_AMUX_CNTRL_SEL3		BIT(7)
+#define ADC_AMUX_PREMUX_SHIFT			2
+#define ADC_AMUX_SEL_SHIFT			4
+
+/* We know very little about the bits in this register */
+#define ADC_ARB_USRP_ANA_PARAM			0x199
+#define ADC_ARB_USRP_ANA_PARAM_DIS		0xFE
+#define ADC_ARB_USRP_ANA_PARAM_EN		0xFF
+
+#define ADC_ARB_USRP_DIG_PARAM			0x19A
+#define ADC_ARB_USRP_DIG_PARAM_SEL_SHIFT0	BIT(0)
+#define ADC_ARB_USRP_DIG_PARAM_SEL_SHIFT1	BIT(1)
+#define ADC_ARB_USRP_DIG_PARAM_CLK_RATE0	BIT(2)
+#define ADC_ARB_USRP_DIG_PARAM_CLK_RATE1	BIT(3)
+#define ADC_ARB_USRP_DIG_PARAM_EOC		BIT(4)
+/*
+ * On a later ADC the decimation factors are defined as
+ * 00 = 512, 01 = 1024, 10 = 2048, 11 = 4096 so assume this
+ * holds also for this older XOADC.
+ */
+#define ADC_ARB_USRP_DIG_PARAM_DEC_RATE0	BIT(5)
+#define ADC_ARB_USRP_DIG_PARAM_DEC_RATE1	BIT(6)
+#define ADC_ARB_USRP_DIG_PARAM_EN		BIT(7)
+#define ADC_DIG_PARAM_DEC_SHIFT			5
+
+#define ADC_ARB_USRP_RSV			0x19B
+#define ADC_ARB_USRP_RSV_RST			BIT(0)
+#define ADC_ARB_USRP_RSV_DTEST0			BIT(1)
+#define ADC_ARB_USRP_RSV_DTEST1			BIT(2)
+#define ADC_ARB_USRP_RSV_OP			BIT(3)
+#define ADC_ARB_USRP_RSV_IP_SEL0		BIT(4)
+#define ADC_ARB_USRP_RSV_IP_SEL1		BIT(5)
+#define ADC_ARB_USRP_RSV_IP_SEL2		BIT(6)
+#define ADC_ARB_USRP_RSV_TRM			BIT(7)
+#define ADC_RSV_IP_SEL_SHIFT			4
+
+#define ADC_ARB_USRP_DATA0			0x19D
+#define ADC_ARB_USRP_DATA1			0x19C
+
+/**
+ * Physical channels which MUST exist on all PM variants in order to provide
+ * proper reference points for calibration.
+ *
+ * @PM8XXX_CHANNEL_INTERNAL: 625mV reference channel
+ * @PM8XXX_CHANNEL_125V: 1250mV reference channel
+ * @PM8XXX_CHANNEL_INTERNAL_2: 325mV reference channel
+ * @PM8XXX_CHANNEL_MUXOFF: channel to reduce input load on mux, apparently also
+ * measures XO temperature
+ */
+#define PM8XXX_CHANNEL_INTERNAL		0x0c
+#define PM8XXX_CHANNEL_125V		0x0d
+#define PM8XXX_CHANNEL_INTERNAL_2	0x0e
+#define PM8XXX_CHANNEL_MUXOFF		0x0f
+
+/*
+ * PM8058 AMUX premux scaling, two bits. This is done of the channel before
+ * reaching the AMUX.
+ */
+#define PM8058_AMUX_PRESCALE_0 0x0 /* No scaling on the signal */
+#define PM8058_AMUX_PRESCALE_1 0x1 /* Unity scaling selected by the user */
+#define PM8058_AMUX_PRESCALE_1_DIV3 0x2 /* 1/3 prescaler on the input */
+
+/* Defines reference voltage for the XOADC */
+#define AMUX_RSV0 0x0 /* XO_IN/XOADC_GND, special selection to read XO temp */
+#define AMUX_RSV1 0x1 /* PMIC_IN/XOADC_GND */
+#define AMUX_RSV2 0x2 /* PMIC_IN/BMS_CSP */
+#define AMUX_RSV3 0x3 /* not used */
+#define AMUX_RSV4 0x4 /* XOADC_GND/XOADC_GND */
+#define AMUX_RSV5 0x5 /* XOADC_VREF/XOADC_GND */
+#define XOADC_RSV_MAX 5 /* 3 bits 0..7, 3 and 6,7 are invalid */
+
+/**
+ * struct xoadc_channel - encodes channel properties and defaults
+ * @datasheet_name: the hardwarename of this channel
+ * @pre_scale_mux: prescale (PM8058) or premux (PM8921) for selecting
+ * this channel. Both this and the amux channel is needed to uniquely
+ * identify a channel. Values 0..3.
+ * @amux_channel: value of the ADC_ARB_USRP_AMUX_CNTRL register for this
+ * channel, bits 4..7, selects the amux, values 0..f
+ * @prescale: the channels have hard-coded prescale ratios defined
+ * by the hardware, this tells us what it is
+ * @type: corresponding IIO channel type, usually IIO_VOLTAGE or
+ * IIO_TEMP
+ * @scale_fn_type: the liner interpolation etc to convert the
+ * ADC code to the value that IIO expects, in uV or millicelsius
+ * etc. This scale function can be pretty elaborate if different
+ * thermistors are connected or other hardware characteristics are
+ * deployed.
+ * @amux_ip_rsv: ratiometric scale value used by the analog muxer: this
+ * selects the reference voltage for ratiometric scaling
+ */
+struct xoadc_channel {
+	const char *datasheet_name;
+	u8 pre_scale_mux:2;
+	u8 amux_channel:4;
+	const struct vadc_prescale_ratio prescale;
+	enum iio_chan_type type;
+	enum vadc_scale_fn_type scale_fn_type;
+	u8 amux_ip_rsv:3;
+};
+
+/**
+ * struct xoadc_variant - encodes the XOADC variant characteristics
+ * @name: name of this PMIC variant
+ * @channels: the hardware channels and respective settings and defaults
+ * @broken_ratiometric: if the PMIC has broken ratiometric scaling (this
+ * is a known problem on PM8058)
+ * @prescaling: this variant uses AMUX bits 2 & 3 for prescaling (PM8058)
+ * @second_level_mux: this variant uses AMUX bits 2 & 3 for a second level
+ * mux
+ */
+struct xoadc_variant {
+	const char name[16];
+	const struct xoadc_channel *channels;
+	bool broken_ratiometric;
+	bool prescaling;
+	bool second_level_mux;
+};
+
+/*
+ * XOADC_CHAN macro parameters:
+ * _dname: the name of the channel
+ * _presmux: prescaler (PM8058) or premux (PM8921) setting for this channel
+ * _amux: the value in bits 2..7 of the ADC_ARB_USRP_AMUX_CNTRL register
+ * for this channel. On some PMICs some of the bits select a prescaler, and
+ * on some PMICs some of the bits select various complex multiplex settings.
+ * _type: IIO channel type
+ * _prenum: prescaler numerator (dividend)
+ * _preden: prescaler denominator (divisor)
+ * _scale: scaling function type, this selects how the raw valued is mangled
+ * to output the actual processed measurement
+ * _amip: analog mux input parent when using ratiometric measurements
+ */
+#define XOADC_CHAN(_dname, _presmux, _amux, _type, _prenum, _preden, _scale, _amip) \
+	{								\
+		.datasheet_name = __stringify(_dname),			\
+		.pre_scale_mux = _presmux,				\
+		.amux_channel = _amux,					\
+		.prescale = { .num = _prenum, .den = _preden },		\
+		.type = _type,						\
+		.scale_fn_type = _scale,				\
+		.amux_ip_rsv = _amip,					\
+	}
+
+/*
+ * Taken from arch/arm/mach-msm/board-9615.c in the vendor tree:
+ * TODO: incomplete, needs testing.
+ */
+static const struct xoadc_channel pm8018_xoadc_channels[] = {
+	XOADC_CHAN(VCOIN, 0x00, 0x00, IIO_VOLTAGE, 1, 3, SCALE_DEFAULT, AMUX_RSV1),
+	XOADC_CHAN(VBAT, 0x00, 0x01, IIO_VOLTAGE, 1, 3, SCALE_DEFAULT, AMUX_RSV1),
+	XOADC_CHAN(VPH_PWR, 0x00, 0x02, IIO_VOLTAGE, 1, 3, SCALE_DEFAULT, AMUX_RSV1),
+	XOADC_CHAN(DIE_TEMP, 0x00, 0x0b, IIO_TEMP, 1, 1, SCALE_PMIC_THERM, AMUX_RSV1),
+	/* Used for battery ID or battery temperature */
+	XOADC_CHAN(AMUX8, 0x00, 0x08, IIO_VOLTAGE, 1, 1, SCALE_DEFAULT, AMUX_RSV2),
+	XOADC_CHAN(INTERNAL, 0x00, 0x0c, IIO_VOLTAGE, 1, 1, SCALE_DEFAULT, AMUX_RSV1),
+	XOADC_CHAN(125V, 0x00, 0x0d, IIO_VOLTAGE, 1, 1, SCALE_DEFAULT, AMUX_RSV1),
+	XOADC_CHAN(MUXOFF, 0x00, 0x0f, IIO_TEMP, 1, 1, SCALE_XOTHERM, AMUX_RSV0),
+	{ }, /* Sentinel */
+};
+
+/*
+ * Taken from arch/arm/mach-msm/board-8930-pmic.c in the vendor tree:
+ * TODO: needs testing.
+ */
+static const struct xoadc_channel pm8038_xoadc_channels[] = {
+	XOADC_CHAN(VCOIN, 0x00, 0x00, IIO_VOLTAGE, 1, 3, SCALE_DEFAULT, AMUX_RSV1),
+	XOADC_CHAN(VBAT, 0x00, 0x01, IIO_VOLTAGE, 1, 3, SCALE_DEFAULT, AMUX_RSV1),
+	XOADC_CHAN(DCIN, 0x00, 0x02, IIO_VOLTAGE, 1, 6, SCALE_DEFAULT, AMUX_RSV1),
+	XOADC_CHAN(ICHG, 0x00, 0x03, IIO_VOLTAGE, 1, 1, SCALE_DEFAULT, AMUX_RSV1),
+	XOADC_CHAN(VPH_PWR, 0x00, 0x04, IIO_VOLTAGE, 1, 3, SCALE_DEFAULT, AMUX_RSV1),
+	XOADC_CHAN(AMUX5, 0x00, 0x05, IIO_VOLTAGE, 1, 1, SCALE_DEFAULT, AMUX_RSV1),
+	XOADC_CHAN(AMUX6, 0x00, 0x06, IIO_VOLTAGE, 1, 1, SCALE_DEFAULT, AMUX_RSV1),
+	XOADC_CHAN(AMUX7, 0x00, 0x07, IIO_VOLTAGE, 1, 1, SCALE_DEFAULT, AMUX_RSV1),
+	/* AMUX8 used for battery temperature in most cases */
+	XOADC_CHAN(AMUX8, 0x00, 0x08, IIO_TEMP, 1, 1, SCALE_THERM_100K_PULLUP, AMUX_RSV2),
+	XOADC_CHAN(AMUX9, 0x00, 0x09, IIO_VOLTAGE, 1, 1, SCALE_DEFAULT, AMUX_RSV1),
+	XOADC_CHAN(USB_VBUS, 0x00, 0x0a, IIO_VOLTAGE, 1, 4, SCALE_DEFAULT, AMUX_RSV1),
+	XOADC_CHAN(DIE_TEMP, 0x00, 0x0b, IIO_TEMP, 1, 1, SCALE_PMIC_THERM, AMUX_RSV1),
+	XOADC_CHAN(INTERNAL, 0x00, 0x0c, IIO_VOLTAGE, 1, 1, SCALE_DEFAULT, AMUX_RSV1),
+	XOADC_CHAN(125V, 0x00, 0x0d, IIO_VOLTAGE, 1, 1, SCALE_DEFAULT, AMUX_RSV1),
+	XOADC_CHAN(INTERNAL_2, 0x00, 0x0e, IIO_VOLTAGE, 1, 1, SCALE_DEFAULT, AMUX_RSV1),
+	XOADC_CHAN(MUXOFF, 0x00, 0x0f, IIO_TEMP, 1, 1, SCALE_XOTHERM, AMUX_RSV0),
+	{ }, /* Sentinel */
+};
+
+/*
+ * This was created by cross-referencing the vendor tree
+ * arch/arm/mach-msm/board-msm8x60.c msm_adc_channels_data[]
+ * with the "channel types" (first field) to find the right
+ * configuration for these channels on an MSM8x60 i.e. PM8058
+ * setup.
+ */
+static const struct xoadc_channel pm8058_xoadc_channels[] = {
+	XOADC_CHAN(VCOIN, 0x00, 0x00, IIO_VOLTAGE, 1, 2, SCALE_DEFAULT, AMUX_RSV1),
+	XOADC_CHAN(VBAT, 0x00, 0x01, IIO_VOLTAGE, 1, 3, SCALE_DEFAULT, AMUX_RSV1),
+	XOADC_CHAN(DCIN, 0x00, 0x02, IIO_VOLTAGE, 1, 10, SCALE_DEFAULT, AMUX_RSV1),
+	XOADC_CHAN(ICHG, 0x00, 0x03, IIO_VOLTAGE, 1, 1, SCALE_DEFAULT, AMUX_RSV1),
+	XOADC_CHAN(VPH_PWR, 0x00, 0x04, IIO_VOLTAGE, 1, 3, SCALE_DEFAULT, AMUX_RSV1),
+	/*
+	 * AMUX channels 5 thru 9 are referred to as MPP5 thru MPP9 in
+	 * some code and documentation. But they are really just 5
+	 * channels just like any other. They are connected to a switching
+	 * matrix where they can be routed to any of the MPPs, not just
+	 * 1-to-1 onto MPP5 thru 9, so naming them MPP5 thru MPP9 is
+	 * very confusing.
+	 */
+	XOADC_CHAN(AMUX5, 0x00, 0x05, IIO_VOLTAGE, 1, 1, SCALE_DEFAULT, AMUX_RSV1),
+	XOADC_CHAN(AMUX6, 0x00, 0x06, IIO_VOLTAGE, 1, 1, SCALE_DEFAULT, AMUX_RSV1),
+	XOADC_CHAN(AMUX7, 0x00, 0x07, IIO_VOLTAGE, 1, 2, SCALE_DEFAULT, AMUX_RSV1),
+	XOADC_CHAN(AMUX8, 0x00, 0x08, IIO_VOLTAGE, 1, 2, SCALE_DEFAULT, AMUX_RSV1),
+	XOADC_CHAN(AMUX9, 0x00, 0x09, IIO_VOLTAGE, 1, 3, SCALE_DEFAULT, AMUX_RSV1),
+	XOADC_CHAN(USB_VBUS, 0x00, 0x0a, IIO_VOLTAGE, 1, 3, SCALE_DEFAULT, AMUX_RSV1),
+	XOADC_CHAN(DIE_TEMP, 0x00, 0x0b, IIO_TEMP, 1, 1, SCALE_PMIC_THERM, AMUX_RSV1),
+	XOADC_CHAN(INTERNAL, 0x00, 0x0c, IIO_VOLTAGE, 1, 1, SCALE_DEFAULT, AMUX_RSV1),
+	XOADC_CHAN(125V, 0x00, 0x0d, IIO_VOLTAGE, 1, 1, SCALE_DEFAULT, AMUX_RSV1),
+	XOADC_CHAN(INTERNAL_2, 0x00, 0x0e, IIO_VOLTAGE, 1, 1, SCALE_DEFAULT, AMUX_RSV1),
+	XOADC_CHAN(MUXOFF, 0x00, 0x0f, IIO_TEMP, 1, 1, SCALE_XOTHERM, AMUX_RSV0),
+	/* There are also "unity" and divided by 3 channels (prescaler) but noone is using them */
+	{ }, /* Sentinel */
+};
+
+/*
+ * The PM8921 has some pre-muxing on its channels, this comes from the vendor tree
+ * include/linux/mfd/pm8xxx/pm8xxx-adc.h
+ * board-flo-pmic.c (Nexus 7) and board-8064-pmic.c
+ */
+static const struct xoadc_channel pm8921_xoadc_channels[] = {
+	XOADC_CHAN(VCOIN, 0x00, 0x00, IIO_VOLTAGE, 1, 3, SCALE_DEFAULT, AMUX_RSV1),
+	XOADC_CHAN(VBAT, 0x00, 0x01, IIO_VOLTAGE, 1, 3, SCALE_DEFAULT, AMUX_RSV1),
+	XOADC_CHAN(DCIN, 0x00, 0x02, IIO_VOLTAGE, 1, 6, SCALE_DEFAULT, AMUX_RSV1),
+	/* channel "ICHG" is reserved and not used on PM8921 */
+	XOADC_CHAN(VPH_PWR, 0x00, 0x04, IIO_VOLTAGE, 1, 3, SCALE_DEFAULT, AMUX_RSV1),
+	XOADC_CHAN(IBAT, 0x00, 0x05, IIO_VOLTAGE, 1, 1, SCALE_DEFAULT, AMUX_RSV1),
+	/* CHAN 6 & 7 (MPP1 & MPP2) are reserved for MPP channels on PM8921 */
+	XOADC_CHAN(BATT_THERM, 0x00, 0x08, IIO_TEMP, 1, 1, SCALE_THERM_100K_PULLUP, AMUX_RSV1),
+	XOADC_CHAN(BATT_ID, 0x00, 0x09, IIO_VOLTAGE, 1, 1, SCALE_DEFAULT, AMUX_RSV1),
+	XOADC_CHAN(USB_VBUS, 0x00, 0x0a, IIO_VOLTAGE, 1, 4, SCALE_DEFAULT, AMUX_RSV1),
+	XOADC_CHAN(DIE_TEMP, 0x00, 0x0b, IIO_TEMP, 1, 1, SCALE_PMIC_THERM, AMUX_RSV1),
+	XOADC_CHAN(INTERNAL, 0x00, 0x0c, IIO_VOLTAGE, 1, 1, SCALE_DEFAULT, AMUX_RSV1),
+	XOADC_CHAN(125V, 0x00, 0x0d, IIO_VOLTAGE, 1, 1, SCALE_DEFAULT, AMUX_RSV1),
+	/* FIXME: look into the scaling of this temperature */
+	XOADC_CHAN(CHG_TEMP, 0x00, 0x0e, IIO_TEMP, 1, 1, SCALE_DEFAULT, AMUX_RSV1),
+	XOADC_CHAN(MUXOFF, 0x00, 0x0f, IIO_TEMP, 1, 1, SCALE_XOTHERM, AMUX_RSV0),
+	/* The following channels have premux bit 0 set to 1 (all end in 4) */
+	XOADC_CHAN(ATEST_8, 0x01, 0x00, IIO_VOLTAGE, 1, 1, SCALE_DEFAULT, AMUX_RSV1),
+	/* Set scaling to 1/2 based on the name for these two */
+	XOADC_CHAN(USB_SNS_DIV20, 0x01, 0x01, IIO_VOLTAGE, 1, 2, SCALE_DEFAULT, AMUX_RSV1),
+	XOADC_CHAN(DCIN_SNS_DIV20, 0x01, 0x02, IIO_VOLTAGE, 1, 2, SCALE_DEFAULT, AMUX_RSV1),
+	XOADC_CHAN(AMUX3, 0x01, 0x03, IIO_VOLTAGE, 1, 1, SCALE_DEFAULT, AMUX_RSV1),
+	XOADC_CHAN(AMUX4, 0x01, 0x04, IIO_VOLTAGE, 1, 1, SCALE_DEFAULT, AMUX_RSV1),
+	XOADC_CHAN(AMUX5, 0x01, 0x05, IIO_VOLTAGE, 1, 1, SCALE_DEFAULT, AMUX_RSV1),
+	XOADC_CHAN(AMUX6, 0x01, 0x06, IIO_VOLTAGE, 1, 1, SCALE_DEFAULT, AMUX_RSV1),
+	XOADC_CHAN(AMUX7, 0x01, 0x07, IIO_VOLTAGE, 1, 1, SCALE_DEFAULT, AMUX_RSV1),
+	XOADC_CHAN(AMUX8, 0x01, 0x08, IIO_VOLTAGE, 1, 1, SCALE_DEFAULT, AMUX_RSV1),
+	/* Internal test signals, I think */
+	XOADC_CHAN(ATEST_1, 0x01, 0x09, IIO_VOLTAGE, 1, 1, SCALE_DEFAULT, AMUX_RSV1),
+	XOADC_CHAN(ATEST_2, 0x01, 0x0a, IIO_VOLTAGE, 1, 1, SCALE_DEFAULT, AMUX_RSV1),
+	XOADC_CHAN(ATEST_3, 0x01, 0x0b, IIO_VOLTAGE, 1, 1, SCALE_DEFAULT, AMUX_RSV1),
+	XOADC_CHAN(ATEST_4, 0x01, 0x0c, IIO_VOLTAGE, 1, 1, SCALE_DEFAULT, AMUX_RSV1),
+	XOADC_CHAN(ATEST_5, 0x01, 0x0d, IIO_VOLTAGE, 1, 1, SCALE_DEFAULT, AMUX_RSV1),
+	XOADC_CHAN(ATEST_6, 0x01, 0x0e, IIO_VOLTAGE, 1, 1, SCALE_DEFAULT, AMUX_RSV1),
+	XOADC_CHAN(ATEST_7, 0x01, 0x0f, IIO_VOLTAGE, 1, 1, SCALE_DEFAULT, AMUX_RSV1),
+	/* The following channels have premux bit 1 set to 1 (all end in 8) */
+	/* I guess even ATEST8 will be divided by 3 here */
+	XOADC_CHAN(ATEST_8, 0x02, 0x00, IIO_VOLTAGE, 1, 3, SCALE_DEFAULT, AMUX_RSV1),
+	/* I guess div 2 div 3 becomes div 6 */
+	XOADC_CHAN(USB_SNS_DIV20_DIV3, 0x02, 0x01, IIO_VOLTAGE, 1, 6, SCALE_DEFAULT, AMUX_RSV1),
+	XOADC_CHAN(DCIN_SNS_DIV20_DIV3, 0x02, 0x02, IIO_VOLTAGE, 1, 6, SCALE_DEFAULT, AMUX_RSV1),
+	XOADC_CHAN(AMUX3_DIV3, 0x02, 0x03, IIO_VOLTAGE, 1, 3, SCALE_DEFAULT, AMUX_RSV1),
+	XOADC_CHAN(AMUX4_DIV3, 0x02, 0x04, IIO_VOLTAGE, 1, 3, SCALE_DEFAULT, AMUX_RSV1),
+	XOADC_CHAN(AMUX5_DIV3, 0x02, 0x05, IIO_VOLTAGE, 1, 3, SCALE_DEFAULT, AMUX_RSV1),
+	XOADC_CHAN(AMUX6_DIV3, 0x02, 0x06, IIO_VOLTAGE, 1, 3, SCALE_DEFAULT, AMUX_RSV1),
+	XOADC_CHAN(AMUX7_DIV3, 0x02, 0x07, IIO_VOLTAGE, 1, 3, SCALE_DEFAULT, AMUX_RSV1),
+	XOADC_CHAN(AMUX8_DIV3, 0x02, 0x08, IIO_VOLTAGE, 1, 3, SCALE_DEFAULT, AMUX_RSV1),
+	XOADC_CHAN(ATEST_1_DIV3, 0x02, 0x09, IIO_VOLTAGE, 1, 3, SCALE_DEFAULT, AMUX_RSV1),
+	XOADC_CHAN(ATEST_2_DIV3, 0x02, 0x0a, IIO_VOLTAGE, 1, 3, SCALE_DEFAULT, AMUX_RSV1),
+	XOADC_CHAN(ATEST_3_DIV3, 0x02, 0x0b, IIO_VOLTAGE, 1, 3, SCALE_DEFAULT, AMUX_RSV1),
+	XOADC_CHAN(ATEST_4_DIV3, 0x02, 0x0c, IIO_VOLTAGE, 1, 3, SCALE_DEFAULT, AMUX_RSV1),
+	XOADC_CHAN(ATEST_5_DIV3, 0x02, 0x0d, IIO_VOLTAGE, 1, 3, SCALE_DEFAULT, AMUX_RSV1),
+	XOADC_CHAN(ATEST_6_DIV3, 0x02, 0x0e, IIO_VOLTAGE, 1, 3, SCALE_DEFAULT, AMUX_RSV1),
+	XOADC_CHAN(ATEST_7_DIV3, 0x02, 0x0f, IIO_VOLTAGE, 1, 3, SCALE_DEFAULT, AMUX_RSV1),
+	{ }, /* Sentinel */
+};
+
+/**
+ * struct pm8xxx_chan_info - ADC channel information
+ * @name: name of this channel
+ * @hwchan: pointer to hardware channel information (muxing & scaling settings)
+ * @calibration: whether to use absolute or ratiometric calibration
+ * @scale_fn_type: scaling function type
+ * @decimation: 0,1,2,3
+ * @amux_ip_rsv: ratiometric scale value if using ratiometric
+ * calibration: 0, 1, 2, 4, 5.
+ */
+struct pm8xxx_chan_info {
+	const char *name;
+	const struct xoadc_channel *hwchan;
+	enum vadc_calibration calibration;
+	u8 decimation:2;
+	u8 amux_ip_rsv:3;
+};
+
+/**
+ * struct pm8xxx_xoadc - state container for the XOADC
+ * @dev: pointer to device
+ * @map: regmap to access registers
+ * @vref: reference voltage regulator
+ * characteristics of the channels, and sensible default settings
+ * @nchans: number of channels, configured by the device tree
+ * @chans: the channel information per-channel, configured by the device tree
+ * @iio_chans: IIO channel specifiers
+ * @graph: linear calibration parameters for absolute and
+ * ratiometric measurements
+ * @complete: completion to indicate end of conversion
+ * @lock: lock to restrict access to the hardware to one client at the time
+ */
+struct pm8xxx_xoadc {
+	struct device *dev;
+	struct regmap *map;
+	const struct xoadc_variant *variant;
+	struct regulator *vref;
+	unsigned int nchans;
+	struct pm8xxx_chan_info *chans;
+	struct iio_chan_spec *iio_chans;
+	struct vadc_linear_graph graph[2];
+	struct completion complete;
+	struct mutex lock;
+};
+
+static irqreturn_t pm8xxx_eoc_irq(int irq, void *d)
+{
+	struct iio_dev *indio_dev = d;
+	struct pm8xxx_xoadc *adc = iio_priv(indio_dev);
+
+	complete(&adc->complete);
+
+	return IRQ_HANDLED;
+}
+
+static struct pm8xxx_chan_info *
+pm8xxx_get_channel(struct pm8xxx_xoadc *adc, u8 chan)
+{
+	struct pm8xxx_chan_info *ch;
+	int i;
+
+	for (i = 0; i < adc->nchans; i++) {
+		ch = &adc->chans[i];
+		if (ch->hwchan->amux_channel == chan)
+			break;
+	}
+	if (i == adc->nchans)
+		return NULL;
+
+	return ch;
+}
+
+static int pm8xxx_read_channel_rsv(struct pm8xxx_xoadc *adc,
+				   const struct pm8xxx_chan_info *ch,
+				   u8 rsv, u16 *adc_code,
+				   bool force_ratiometric)
+{
+	int ret;
+	unsigned int val;
+	u8 rsvmask, rsvval;
+	u8 lsb, msb;
+
+	dev_dbg(adc->dev, "read channel \"%s\", amux %d, prescale/mux: %d, rsv %d\n",
+		ch->name, ch->hwchan->amux_channel, ch->hwchan->pre_scale_mux, rsv);
+
+	mutex_lock(&adc->lock);
+
+	/* Mux in this channel */
+	val = ch->hwchan->amux_channel << ADC_AMUX_SEL_SHIFT;
+	val |= ch->hwchan->pre_scale_mux << ADC_AMUX_PREMUX_SHIFT;
+	ret = regmap_write(adc->map, ADC_ARB_USRP_AMUX_CNTRL, val);
+	if (ret)
+		goto unlock;
+
+	/* Set up ratiometric scale value, mask off all bits except these */
+	rsvmask = (ADC_ARB_USRP_RSV_RST | ADC_ARB_USRP_RSV_DTEST0 |
+		   ADC_ARB_USRP_RSV_DTEST1 | ADC_ARB_USRP_RSV_OP);
+	if (adc->variant->broken_ratiometric && !force_ratiometric) {
+		/*
+		 * Apparently the PM8058 has some kind of bug which is
+		 * reflected in the vendor tree drivers/misc/pmix8058-xoadc.c
+		 * which just hardcodes the RSV selector to SEL1 (0x20) for
+		 * most cases and SEL0 (0x10) for the MUXOFF channel only.
+		 * If we force ratiometric (currently only done when attempting
+		 * to do ratiometric calibration) this doesn't seem to work
+		 * very well and I suspect ratiometric conversion is simply
+		 * broken or not supported on the PM8058.
+		 *
+		 * Maybe IO_SEL2 doesn't exist on PM8058 and bits 4 & 5 select
+		 * the mode alone.
+		 *
+		 * Some PM8058 register documentation would be nice to get
+		 * this right.
+		 */
+		if (ch->hwchan->amux_channel == PM8XXX_CHANNEL_MUXOFF)
+			rsvval = ADC_ARB_USRP_RSV_IP_SEL0;
+		else
+			rsvval = ADC_ARB_USRP_RSV_IP_SEL1;
+	} else {
+		if (rsv == 0xff)
+			rsvval = (ch->amux_ip_rsv << ADC_RSV_IP_SEL_SHIFT) |
+				ADC_ARB_USRP_RSV_TRM;
+		else
+			rsvval = (rsv << ADC_RSV_IP_SEL_SHIFT) |
+				ADC_ARB_USRP_RSV_TRM;
+	}
+
+	ret = regmap_update_bits(adc->map,
+				 ADC_ARB_USRP_RSV,
+				 ~rsvmask,
+				 rsvval);
+	if (ret)
+		goto unlock;
+
+	ret = regmap_write(adc->map, ADC_ARB_USRP_ANA_PARAM,
+			   ADC_ARB_USRP_ANA_PARAM_DIS);
+	if (ret)
+		goto unlock;
+
+	/* Decimation factor */
+	ret = regmap_write(adc->map, ADC_ARB_USRP_DIG_PARAM,
+			   ADC_ARB_USRP_DIG_PARAM_SEL_SHIFT0 |
+			   ADC_ARB_USRP_DIG_PARAM_SEL_SHIFT1 |
+			   ch->decimation << ADC_DIG_PARAM_DEC_SHIFT);
+	if (ret)
+		goto unlock;
+
+	ret = regmap_write(adc->map, ADC_ARB_USRP_ANA_PARAM,
+			   ADC_ARB_USRP_ANA_PARAM_EN);
+	if (ret)
+		goto unlock;
+
+	/* Enable the arbiter, the Qualcomm code does it twice like this */
+	ret = regmap_write(adc->map, ADC_ARB_USRP_CNTRL,
+			   ADC_ARB_USRP_CNTRL_EN_ARB);
+	if (ret)
+		goto unlock;
+	ret = regmap_write(adc->map, ADC_ARB_USRP_CNTRL,
+			   ADC_ARB_USRP_CNTRL_EN_ARB);
+	if (ret)
+		goto unlock;
+
+
+	/* Fire a request! */
+	reinit_completion(&adc->complete);
+	ret = regmap_write(adc->map, ADC_ARB_USRP_CNTRL,
+			   ADC_ARB_USRP_CNTRL_EN_ARB |
+			   ADC_ARB_USRP_CNTRL_REQ);
+	if (ret)
+		goto unlock;
+
+	/* Next the interrupt occurs */
+	ret = wait_for_completion_timeout(&adc->complete,
+					  VADC_CONV_TIME_MAX_US);
+	if (!ret) {
+		dev_err(adc->dev, "conversion timed out\n");
+		ret = -ETIMEDOUT;
+		goto unlock;
+	}
+
+	ret = regmap_read(adc->map, ADC_ARB_USRP_DATA0, &val);
+	if (ret)
+		goto unlock;
+	lsb = val;
+	ret = regmap_read(adc->map, ADC_ARB_USRP_DATA1, &val);
+	if (ret)
+		goto unlock;
+	msb = val;
+	*adc_code = (msb << 8) | lsb;
+
+	/* Turn off the ADC by setting the arbiter to 0 twice */
+	ret = regmap_write(adc->map, ADC_ARB_USRP_CNTRL, 0);
+	if (ret)
+		goto unlock;
+	ret = regmap_write(adc->map, ADC_ARB_USRP_CNTRL, 0);
+	if (ret)
+		goto unlock;
+
+unlock:
+	mutex_unlock(&adc->lock);
+	return ret;
+}
+
+static int pm8xxx_read_channel(struct pm8xxx_xoadc *adc,
+			       const struct pm8xxx_chan_info *ch,
+			       u16 *adc_code)
+{
+	/*
+	 * Normally we just use the ratiometric scale value (RSV) predefined
+	 * for the channel, but during calibration we need to modify this
+	 * so this wrapper is a helper hiding the more complex version.
+	 */
+	return pm8xxx_read_channel_rsv(adc, ch, 0xff, adc_code, false);
+}
+
+static int pm8xxx_calibrate_device(struct pm8xxx_xoadc *adc)
+{
+	const struct pm8xxx_chan_info *ch;
+	u16 read_1250v;
+	u16 read_0625v;
+	u16 read_nomux_rsv5;
+	u16 read_nomux_rsv4;
+	int ret;
+
+	adc->graph[VADC_CALIB_ABSOLUTE].dx = VADC_ABSOLUTE_RANGE_UV;
+	adc->graph[VADC_CALIB_RATIOMETRIC].dx = VADC_RATIOMETRIC_RANGE;
+
+	/* Common reference channel calibration */
+	ch = pm8xxx_get_channel(adc, PM8XXX_CHANNEL_125V);
+	if (!ch)
+		return -ENODEV;
+	ret = pm8xxx_read_channel(adc, ch, &read_1250v);
+	if (ret) {
+		dev_err(adc->dev, "could not read 1.25V reference channel\n");
+		return -ENODEV;
+	}
+	ch = pm8xxx_get_channel(adc, PM8XXX_CHANNEL_INTERNAL);
+	if (!ch)
+		return -ENODEV;
+	ret = pm8xxx_read_channel(adc, ch, &read_0625v);
+	if (ret) {
+		dev_err(adc->dev, "could not read 0.625V reference channel\n");
+		return -ENODEV;
+	}
+	if (read_1250v == read_0625v) {
+		dev_err(adc->dev, "read same ADC code for 1.25V and 0.625V\n");
+		return -ENODEV;
+	}
+
+	adc->graph[VADC_CALIB_ABSOLUTE].dy = read_1250v - read_0625v;
+	adc->graph[VADC_CALIB_ABSOLUTE].gnd = read_0625v;
+
+	dev_info(adc->dev, "absolute calibration dx = %d uV, dy = %d units\n",
+		 VADC_ABSOLUTE_RANGE_UV, adc->graph[VADC_CALIB_ABSOLUTE].dy);
+
+	/* Ratiometric calibration */
+	ch = pm8xxx_get_channel(adc, PM8XXX_CHANNEL_MUXOFF);
+	if (!ch)
+		return -ENODEV;
+	ret = pm8xxx_read_channel_rsv(adc, ch, AMUX_RSV5,
+				      &read_nomux_rsv5, true);
+	if (ret) {
+		dev_err(adc->dev, "could not read MUXOFF reference channel\n");
+		return -ENODEV;
+	}
+	ret = pm8xxx_read_channel_rsv(adc, ch, AMUX_RSV4,
+				      &read_nomux_rsv4, true);
+	if (ret) {
+		dev_err(adc->dev, "could not read MUXOFF reference channel\n");
+		return -ENODEV;
+	}
+	adc->graph[VADC_CALIB_RATIOMETRIC].dy =
+		read_nomux_rsv5 - read_nomux_rsv4;
+	adc->graph[VADC_CALIB_RATIOMETRIC].gnd = read_nomux_rsv4;
+
+	dev_info(adc->dev, "ratiometric calibration dx = %d, dy = %d units\n",
+		 VADC_RATIOMETRIC_RANGE,
+		 adc->graph[VADC_CALIB_RATIOMETRIC].dy);
+
+	return 0;
+}
+
+static int pm8xxx_read_raw(struct iio_dev *indio_dev,
+			   struct iio_chan_spec const *chan,
+			   int *val, int *val2, long mask)
+{
+	struct pm8xxx_xoadc *adc = iio_priv(indio_dev);
+	const struct pm8xxx_chan_info *ch;
+	u16 adc_code;
+	int ret;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_PROCESSED:
+		ch = pm8xxx_get_channel(adc, chan->address);
+		if (!ch) {
+			dev_err(adc->dev, "no such channel %lu\n",
+				chan->address);
+			return -EINVAL;
+		}
+		ret = pm8xxx_read_channel(adc, ch, &adc_code);
+		if (ret)
+			return ret;
+
+		ret = qcom_vadc_scale(ch->hwchan->scale_fn_type,
+				      &adc->graph[ch->calibration],
+				      &ch->hwchan->prescale,
+				      (ch->calibration == VADC_CALIB_ABSOLUTE),
+				      adc_code, val);
+		if (ret)
+			return ret;
+
+		return IIO_VAL_INT;
+	case IIO_CHAN_INFO_RAW:
+		ch = pm8xxx_get_channel(adc, chan->address);
+		if (!ch) {
+			dev_err(adc->dev, "no such channel %lu\n",
+				chan->address);
+			return -EINVAL;
+		}
+		ret = pm8xxx_read_channel(adc, ch, &adc_code);
+		if (ret)
+			return ret;
+
+		*val = (int)adc_code;
+		return IIO_VAL_INT;
+	default:
+		return -EINVAL;
+	}
+}
+
+static int pm8xxx_of_xlate(struct iio_dev *indio_dev,
+			   const struct of_phandle_args *iiospec)
+{
+	struct pm8xxx_xoadc *adc = iio_priv(indio_dev);
+	u8 pre_scale_mux;
+	u8 amux_channel;
+	unsigned int i;
+
+	/*
+	 * First cell is prescaler or premux, second cell is analog
+	 * mux.
+	 */
+	if (iiospec->args_count != 2) {
+		dev_err(&indio_dev->dev, "wrong number of arguments for %s need 2 got %d\n",
+			iiospec->np->name,
+			iiospec->args_count);
+		return -EINVAL;
+	}
+	pre_scale_mux = (u8)iiospec->args[0];
+	amux_channel = (u8)iiospec->args[1];
+	dev_dbg(&indio_dev->dev, "pre scale/mux: %02x, amux: %02x\n",
+		pre_scale_mux, amux_channel);
+
+	/* We need to match exactly on the prescale/premux and channel */
+	for (i = 0; i < adc->nchans; i++)
+		if (adc->chans[i].hwchan->pre_scale_mux == pre_scale_mux &&
+		    adc->chans[i].hwchan->amux_channel == amux_channel)
+			return i;
+
+	return -EINVAL;
+}
+
+static const struct iio_info pm8xxx_xoadc_info = {
+	.driver_module = THIS_MODULE,
+	.of_xlate = pm8xxx_of_xlate,
+	.read_raw = pm8xxx_read_raw,
+};
+
+static int pm8xxx_xoadc_parse_channel(struct device *dev,
+				      struct device_node *np,
+				      const struct xoadc_channel *hw_channels,
+				      struct iio_chan_spec *iio_chan,
+				      struct pm8xxx_chan_info *ch)
+{
+	const char *name = np->name;
+	const struct xoadc_channel *hwchan;
+	u32 pre_scale_mux, amux_channel;
+	u32 rsv, dec;
+	int ret;
+	int chid;
+
+	ret = of_property_read_u32_index(np, "reg", 0, &pre_scale_mux);
+	if (ret) {
+		dev_err(dev, "invalid pre scale/mux number %s\n", name);
+		return ret;
+	}
+	ret = of_property_read_u32_index(np, "reg", 1, &amux_channel);
+	if (ret) {
+		dev_err(dev, "invalid amux channel number %s\n", name);
+		return ret;
+	}
+
+	/* Find the right channel setting */
+	chid = 0;
+	hwchan = &hw_channels[0];
+	while (hwchan && hwchan->datasheet_name) {
+		if (hwchan->pre_scale_mux == pre_scale_mux &&
+		    hwchan->amux_channel == amux_channel)
+			break;
+		hwchan++;
+		chid++;
+	}
+	/* The sentinel does not have a name assigned */
+	if (!hwchan->datasheet_name) {
+		dev_err(dev, "could not locate channel %02x/%02x\n",
+			pre_scale_mux, amux_channel);
+		return -EINVAL;
+	}
+	ch->name = name;
+	ch->hwchan = hwchan;
+	/* Everyone seems to use absolute calibration except in special cases */
+	ch->calibration = VADC_CALIB_ABSOLUTE;
+	/* Everyone seems to use default ("type 2") decimation */
+	ch->decimation = VADC_DEF_DECIMATION;
+
+	if (!of_property_read_u32(np, "qcom,ratiometric", &rsv)) {
+		ch->calibration = VADC_CALIB_RATIOMETRIC;
+		if (rsv > XOADC_RSV_MAX) {
+			dev_err(dev, "%s too large RSV value %d\n", name, rsv);
+			return -EINVAL;
+		}
+		if (rsv == AMUX_RSV3) {
+			dev_err(dev, "%s invalid RSV value %d\n", name, rsv);
+			return -EINVAL;
+		}
+	}
+
+	/* Optional decimation, if omitted we use the default */
+	ret = of_property_read_u32(np, "qcom,decimation", &dec);
+	if (!ret) {
+		ret = qcom_vadc_decimation_from_dt(dec);
+		if (ret < 0) {
+			dev_err(dev, "%s invalid decimation %d\n",
+				name, dec);
+			return ret;
+		}
+		ch->decimation = ret;
+	}
+
+	iio_chan->channel = chid;
+	iio_chan->address = hwchan->amux_channel;
+	iio_chan->datasheet_name = hwchan->datasheet_name;
+	iio_chan->type = hwchan->type;
+	/* All channels are raw or processed */
+	iio_chan->info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
+		BIT(IIO_CHAN_INFO_PROCESSED);
+	iio_chan->indexed = 1;
+
+	dev_dbg(dev, "channel [PRESCALE/MUX: %02x AMUX: %02x] \"%s\" "
+		"ref voltage: %d, decimation %d "
+		"prescale %d/%d, scale function %d\n",
+		hwchan->pre_scale_mux, hwchan->amux_channel, ch->name,
+		ch->amux_ip_rsv, ch->decimation, hwchan->prescale.num,
+		hwchan->prescale.den, hwchan->scale_fn_type);
+
+	return 0;
+}
+
+static int pm8xxx_xoadc_parse_channels(struct pm8xxx_xoadc *adc,
+				       struct device_node *np)
+{
+	struct device_node *child;
+	struct pm8xxx_chan_info *ch;
+	int ret;
+	int i;
+
+	adc->nchans = of_get_available_child_count(np);
+	if (!adc->nchans) {
+		dev_err(adc->dev, "no channel children\n");
+		return -ENODEV;
+	}
+	dev_dbg(adc->dev, "found %d ADC channels\n", adc->nchans);
+
+	adc->iio_chans = devm_kcalloc(adc->dev, adc->nchans,
+				      sizeof(*adc->iio_chans), GFP_KERNEL);
+	if (!adc->iio_chans)
+		return -ENOMEM;
+
+	adc->chans = devm_kcalloc(adc->dev, adc->nchans,
+				  sizeof(*adc->chans), GFP_KERNEL);
+	if (!adc->chans)
+		return -ENOMEM;
+
+	i = 0;
+	for_each_available_child_of_node(np, child) {
+		ch = &adc->chans[i];
+		ret = pm8xxx_xoadc_parse_channel(adc->dev, child,
+						 adc->variant->channels,
+						 &adc->iio_chans[i],
+						 ch);
+		if (ret) {
+			of_node_put(child);
+			return ret;
+		}
+		i++;
+	}
+
+	/* Check for required channels */
+	ch = pm8xxx_get_channel(adc, PM8XXX_CHANNEL_125V);
+	if (!ch) {
+		dev_err(adc->dev, "missing 1.25V reference channel\n");
+		return -ENODEV;
+	}
+	ch = pm8xxx_get_channel(adc, PM8XXX_CHANNEL_INTERNAL);
+	if (!ch) {
+		dev_err(adc->dev, "missing 0.625V reference channel\n");
+		return -ENODEV;
+	}
+	ch = pm8xxx_get_channel(adc, PM8XXX_CHANNEL_MUXOFF);
+	if (!ch) {
+		dev_err(adc->dev, "missing MUXOFF reference channel\n");
+		return -ENODEV;
+	}
+
+	return 0;
+}
+
+static int pm8xxx_xoadc_probe(struct platform_device *pdev)
+{
+	const struct xoadc_variant *variant;
+	struct pm8xxx_xoadc *adc;
+	struct iio_dev *indio_dev;
+	struct device_node *np = pdev->dev.of_node;
+	struct regmap *map;
+	struct device *dev = &pdev->dev;
+	int ret;
+
+	variant = of_device_get_match_data(dev);
+	if (!variant)
+		return -ENODEV;
+
+	indio_dev = devm_iio_device_alloc(dev, sizeof(*adc));
+	if (!indio_dev)
+		return -ENOMEM;
+	platform_set_drvdata(pdev, indio_dev);
+
+	adc = iio_priv(indio_dev);
+	adc->dev = dev;
+	adc->variant = variant;
+	init_completion(&adc->complete);
+	mutex_init(&adc->lock);
+
+	ret = pm8xxx_xoadc_parse_channels(adc, np);
+	if (ret)
+		return ret;
+
+	map = dev_get_regmap(dev->parent, NULL);
+	if (!map) {
+		dev_err(dev, "parent regmap unavailable.\n");
+		return -ENXIO;
+	}
+	adc->map = map;
+
+	/* Bring up regulator */
+	adc->vref = devm_regulator_get(dev, "xoadc-ref");
+	if (IS_ERR(adc->vref)) {
+		dev_err(dev, "failed to get XOADC VREF regulator\n");
+		return PTR_ERR(adc->vref);
+	}
+	ret = regulator_enable(adc->vref);
+	if (ret) {
+		dev_err(dev, "failed to enable XOADC VREF regulator\n");
+		return ret;
+	}
+
+	ret = devm_request_threaded_irq(dev, platform_get_irq(pdev, 0),
+			pm8xxx_eoc_irq, NULL, 0, variant->name, indio_dev);
+	if (ret) {
+		dev_err(dev, "unable to request IRQ\n");
+		goto out_disable_vref;
+	}
+
+	indio_dev->dev.parent = dev;
+	indio_dev->dev.of_node = np;
+	indio_dev->name = variant->name;
+	indio_dev->modes = INDIO_DIRECT_MODE;
+	indio_dev->info = &pm8xxx_xoadc_info;
+	indio_dev->channels = adc->iio_chans;
+	indio_dev->num_channels = adc->nchans;
+
+	ret = iio_device_register(indio_dev);
+	if (ret)
+		goto out_disable_vref;
+
+	ret = pm8xxx_calibrate_device(adc);
+	if (ret)
+		goto out_unreg_device;
+
+	dev_info(dev, "%s XOADC driver enabled\n", variant->name);
+
+	return 0;
+
+out_unreg_device:
+	iio_device_unregister(indio_dev);
+out_disable_vref:
+	regulator_disable(adc->vref);
+
+	return ret;
+}
+
+static int pm8xxx_xoadc_remove(struct platform_device *pdev)
+{
+	struct iio_dev *indio_dev = platform_get_drvdata(pdev);
+	struct pm8xxx_xoadc *adc = iio_priv(indio_dev);
+
+	iio_device_unregister(indio_dev);
+
+	regulator_disable(adc->vref);
+
+	return 0;
+}
+
+static const struct xoadc_variant pm8018_variant = {
+	.name = "PM8018-XOADC",
+	.channels = pm8018_xoadc_channels,
+};
+
+static const struct xoadc_variant pm8038_variant = {
+	.name = "PM8038-XOADC",
+	.channels = pm8038_xoadc_channels,
+};
+
+static const struct xoadc_variant pm8058_variant = {
+	.name = "PM8058-XOADC",
+	.channels = pm8058_xoadc_channels,
+	.broken_ratiometric = true,
+	.prescaling = true,
+};
+
+static const struct xoadc_variant pm8921_variant = {
+	.name = "PM8921-XOADC",
+	.channels = pm8921_xoadc_channels,
+	.second_level_mux = true,
+};
+
+static const struct of_device_id pm8xxx_xoadc_id_table[] = {
+	{
+		.compatible = "qcom,pm8018-adc",
+		.data = &pm8018_variant,
+	},
+	{
+		.compatible = "qcom,pm8038-adc",
+		.data = &pm8038_variant,
+	},
+	{
+		.compatible = "qcom,pm8058-adc",
+		.data = &pm8058_variant,
+	},
+	{
+		.compatible = "qcom,pm8921-adc",
+		.data = &pm8921_variant,
+	},
+	{ },
+};
+MODULE_DEVICE_TABLE(of, pm8xxx_xoadc_id_table);
+
+static struct platform_driver pm8xxx_xoadc_driver = {
+	.driver		= {
+		.name	= "pm8xxx-adc",
+		.of_match_table = pm8xxx_xoadc_id_table,
+	},
+	.probe		= pm8xxx_xoadc_probe,
+	.remove		= pm8xxx_xoadc_remove,
+};
+module_platform_driver(pm8xxx_xoadc_driver);
+
+MODULE_DESCRIPTION("PM8xxx XOADC driver");
+MODULE_LICENSE("GPL v2");
+MODULE_ALIAS("platform:pm8xxx-xoadc");