[PATCH v4 0/4] iio: adc: Maxim max9611 driver

[PATCH v4 0/4] iio: adc: Maxim max9611 driver

[Jacopo Mondi]

Hello,
   fourth round for max9611 driver.

Biggest shift from v3 is change in locking, now performed only at
read_single() level.
No locking in read_raw, nor in read_csa_voltage(), as the only thing to
protect is the on-chip mux configuration between and I2c write and a read.
All other functions end up in calling this read_single() one, and they do not
share variables, so concurrent accesses to sysfs attributes should be safe.

Changed scale of temperature channel, and fixed shunt resistor names, that now
appears as properties of their respective power and current channels.

Ack on dt-bindings for "shunt-resistor-ohm" property pending from device
tree guardians.

Output of iio_info on Salvator-X board for max9611 chip installed on
VDD_0.8 lines.
The VDD_0.8 line powers the CPU cluster and on-board RAM.

        iio:device0: max9611
                5 channels found:
                        voltage0:  (input)
                        1 channel-specific attributes found:
                                attr 0: input value: 4.085000000
                        voltage1:  (input)
                        3 channel-specific attributes found:
                                attr 0: scale value: 14
                                attr 1: offset value: 1
                                attr 2: raw value: 59
                        power:  (input)
                        2 channel-specific attributes found:
                                attr 0: shunt_resistor value: 5000
                                attr 1: input value: 663.404000000
                        current:  (input)
                        2 channel-specific attributes found:
                                attr 0: shunt_resistor value: 5000
                                attr 1: input value: 817.000000000
                        temp:  (input)
                        2 channel-specific attributes found:
                                attr 0: scale value: 480.076812289
                                attr 1: raw value: 57

The collected information represent:

* voltage0 (current sense voltage) Vcsa
  voltage drop between RS+ and RS- input = 4,085 mV
* voltage1: (common input voltage) Vcim
  voltage at RS+ input = (59 - 1) * 14 = 812 mV
* current flowing on shunt resistor (Icsa)
  = Vcsa / Rshunt = 817 mA
* power load on the sensed line (Pload)
  = Vcim * Icsa = 663 m
* die temperature = (57 * 480.07) = 27360 milli Celsius

Thanks
   j

v1 -> v2:
- Drop wildcard (max961x) in driver, documentation and dt-bindings. Use
  max9611 instead.
- Make 3 processed channels for csa voltage, csa current and power load
- Remove wrapper functions around i2c buffer access
- Add locking in read_raw()
- Make 2 separate attributes for shunt resistor: current and power
- Renamed shunt resistor attribute
- Fixed several review comments

v2 -> v3:
- Incorporated Geert's suggestions on using a more generic name for ADC nodes
  in device tree
- Changed "maxim,shunt-resistor-uohm" to "shunt-resistor-uohm"
- Update documentation accordingly to the two previous changes

v3 -> v4:
- Move all locking to read_single() function
- Re-structure read_raw() with Jonathan's and Peter's comments
- Rename some defines pre-pending MAX9611 prefix
- Use values from .comaptible entries for device name
- Change temperature scale to have a value in milli Celsius
- Simplify init routine using read_single

Jacopo Mondi (4):
  Documentation: dt-bindings: iio: Add max9611 ADC
  iio: Documentation: Add max9611 sysfs documentation
  iio: adc: Add Maxim max9611 ADC driver
  arm64: dts: salvator-x: Add current sense amplifiers

 .../ABI/testing/sysfs-bus-iio-adc-max9611          |  17 +
 .../devicetree/bindings/iio/adc/max9611.txt        |  26 +
 arch/arm64/boot/dts/renesas/r8a7796-salvator-x.dts |  18 +
 drivers/iio/adc/Kconfig                            |  10 +
 drivers/iio/adc/Makefile                           |   1 +
 drivers/iio/adc/max9611.c                          | 583 +++++++++++++++++++++
 6 files changed, 655 insertions(+)
 create mode 100644 Documentation/ABI/testing/sysfs-bus-iio-adc-max9611
 create mode 100644 Documentation/devicetree/bindings/iio/adc/max9611.txt
 create mode 100644 drivers/iio/adc/max9611.c

-- 
2.7.4

[PATCH v4 0/4] iio: adc: Maxim max9611 driver

[Jacopo Mondi]

Hello,
   fourth round for max9611 driver.

Biggest shift from v3 is change in locking, now performed only at
read_single() level.
No locking in read_raw, nor in read_csa_voltage(), as the only thing to
protect is the on-chip mux configuration between and I2c write and a read.
All other functions end up in calling this read_single() one, and they do not
share variables, so concurrent accesses to sysfs attributes should be safe.

Changed scale of temperature channel, and fixed shunt resistor names, that now
appears as properties of their respective power and current channels.

Ack on dt-bindings for "shunt-resistor-ohm" property pending from device
tree guardians.

Output of iio_info on Salvator-X board for max9611 chip installed on
VDD_0.8 lines.
The VDD_0.8 line powers the CPU cluster and on-board RAM.

        iio:device0: max9611
                5 channels found:
                        voltage0:  (input)
                        1 channel-specific attributes found:
                                attr 0: input value: 4.085000000
                        voltage1:  (input)
                        3 channel-specific attributes found:
                                attr 0: scale value: 14
                                attr 1: offset value: 1
                                attr 2: raw value: 59
                        power:  (input)
                        2 channel-specific attributes found:
                                attr 0: shunt_resistor value: 5000
                                attr 1: input value: 663.404000000
                        current:  (input)
                        2 channel-specific attributes found:
                                attr 0: shunt_resistor value: 5000
                                attr 1: input value: 817.000000000
                        temp:  (input)
                        2 channel-specific attributes found:
                                attr 0: scale value: 480.076812289
                                attr 1: raw value: 57

The collected information represent:

* voltage0 (current sense voltage) Vcsa
  voltage drop between RS+ and RS- input = 4,085 mV
* voltage1: (common input voltage) Vcim
  voltage at RS+ input = (59 - 1) * 14 = 812 mV
* current flowing on shunt resistor (Icsa)
  = Vcsa / Rshunt = 817 mA
* power load on the sensed line (Pload)
  = Vcim * Icsa = 663 m
* die temperature = (57 * 480.07) = 27360 milli Celsius

Thanks
   j

v1 -> v2:
- Drop wildcard (max961x) in driver, documentation and dt-bindings. Use
  max9611 instead.
- Make 3 processed channels for csa voltage, csa current and power load
- Remove wrapper functions around i2c buffer access
- Add locking in read_raw()
- Make 2 separate attributes for shunt resistor: current and power
- Renamed shunt resistor attribute
- Fixed several review comments

v2 -> v3:
- Incorporated Geert's suggestions on using a more generic name for ADC nodes
  in device tree
- Changed "maxim,shunt-resistor-uohm" to "shunt-resistor-uohm"
- Update documentation accordingly to the two previous changes

v3 -> v4:
- Move all locking to read_single() function
- Re-structure read_raw() with Jonathan's and Peter's comments
- Rename some defines pre-pending MAX9611 prefix
- Use values from .comaptible entries for device name
- Change temperature scale to have a value in milli Celsius
- Simplify init routine using read_single

Jacopo Mondi (4):
  Documentation: dt-bindings: iio: Add max9611 ADC
  iio: Documentation: Add max9611 sysfs documentation
  iio: adc: Add Maxim max9611 ADC driver
  arm64: dts: salvator-x: Add current sense amplifiers

 .../ABI/testing/sysfs-bus-iio-adc-max9611          |  17 +
 .../devicetree/bindings/iio/adc/max9611.txt        |  26 +
 arch/arm64/boot/dts/renesas/r8a7796-salvator-x.dts |  18 +
 drivers/iio/adc/Kconfig                            |  10 +
 drivers/iio/adc/Makefile                           |   1 +
 drivers/iio/adc/max9611.c                          | 583 +++++++++++++++++++++
 6 files changed, 655 insertions(+)
 create mode 100644 Documentation/ABI/testing/sysfs-bus-iio-adc-max9611
 create mode 100644 Documentation/devicetree/bindings/iio/adc/max9611.txt
 create mode 100644 drivers/iio/adc/max9611.c

-- 
2.7.4

[PATCH v4 1/4] Documentation: dt-bindings: iio: Add max9611 ADC

[Jacopo Mondi]

Add device tree bindings documentation for Maxim max9611/max9612 current
sense amplifier.

Signed-off-by: Jacopo Mondi <jacopo+renesas-AW8dsiIh9cEdnm+yROfE0A@public.gmane.org>
---
 .../devicetree/bindings/iio/adc/max9611.txt        | 26 ++++++++++++++++++++++
 1 file changed, 26 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/iio/adc/max9611.txt

diff --git a/Documentation/devicetree/bindings/iio/adc/max9611.txt b/Documentation/devicetree/bindings/iio/adc/max9611.txt
new file mode 100644
index 0000000..8430d3b
--- /dev/null
+++ b/Documentation/devicetree/bindings/iio/adc/max9611.txt
@@ -0,0 +1,26 @@
+* Maxim max9611/max9612 current sense amplifier with 12-bits ADC interface
+
+Maxim max9611/max9612 is an high-side current sense amplifier with integrated
+12-bits ADC communicating over I2c bus.
+The device node for this driver shall be a child of a I2c controller.
+
+Required properties
+  - compatible: Should be "maxim,max9611" or "maxim,max9612"
+  - reg: The 7-bits long I2c address of the device
+  - shunt-resistor-uohm: Value, in uOhm, of the current sense shunt resistor
+
+Example:
+
+&i2c4 {
+	csa: adc@7c {
+		compatible = "maxim,max9611";
+		reg = <0x7c>;
+
+		shunt-resistor-uohm = <5000>;
+	};
+};
+
+This device node describes a current sense amplifier sitting on I2c4 bus
+with address 0x7c (read address is 0xf9, write address is 0xf8).
+A sense resistor of 0,005 Ohm is installed between RS+ and RS- current-sensing
+inputs.
-- 
2.7.4

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[PATCH v4 1/4] Documentation: dt-bindings: iio: Add max9611 ADC

[Jacopo Mondi]

Add device tree bindings documentation for Maxim max9611/max9612 current
sense amplifier.

Signed-off-by: Jacopo Mondi <jacopo+renesas@jmondi.org>
---
 .../devicetree/bindings/iio/adc/max9611.txt        | 26 ++++++++++++++++++++++
 1 file changed, 26 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/iio/adc/max9611.txt

diff --git a/Documentation/devicetree/bindings/iio/adc/max9611.txt b/Documentation/devicetree/bindings/iio/adc/max9611.txt
new file mode 100644
index 0000000..8430d3b
--- /dev/null
+++ b/Documentation/devicetree/bindings/iio/adc/max9611.txt
@@ -0,0 +1,26 @@
+* Maxim max9611/max9612 current sense amplifier with 12-bits ADC interface
+
+Maxim max9611/max9612 is an high-side current sense amplifier with integrated
+12-bits ADC communicating over I2c bus.
+The device node for this driver shall be a child of a I2c controller.
+
+Required properties
+  - compatible: Should be "maxim,max9611" or "maxim,max9612"
+  - reg: The 7-bits long I2c address of the device
+  - shunt-resistor-uohm: Value, in uOhm, of the current sense shunt resistor
+
+Example:
+
+&i2c4 {
+	csa: adc@7c {
+		compatible = "maxim,max9611";
+		reg = <0x7c>;
+
+		shunt-resistor-uohm = <5000>;
+	};
+};
+
+This device node describes a current sense amplifier sitting on I2c4 bus
+with address 0x7c (read address is 0xf9, write address is 0xf8).
+A sense resistor of 0,005 Ohm is installed between RS+ and RS- current-sensing
+inputs.
-- 
2.7.4

[PATCH v4 2/4] iio: Documentation: Add max9611 sysfs documentation

[Jacopo Mondi]

Add documentation for max9611 driver.
Document attributes describing value of shunt resistor installed between
RS+ and RS- voltage sense inputs.

Signed-off-by: Jacopo Mondi <jacopo+renesas-AW8dsiIh9cEdnm+yROfE0A@public.gmane.org>
---
 Documentation/ABI/testing/sysfs-bus-iio-adc-max9611 | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)
 create mode 100644 Documentation/ABI/testing/sysfs-bus-iio-adc-max9611

diff --git a/Documentation/ABI/testing/sysfs-bus-iio-adc-max9611 b/Documentation/ABI/testing/sysfs-bus-iio-adc-max9611
new file mode 100644
index 0000000..5020d00
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-bus-iio-adc-max9611
@@ -0,0 +1,17 @@
+What:		/sys/bus/iio/devices/iio:deviceX/in_power_shunt_resistor
+Date:		March 2017
+KernelVersion:	4.12
+Contact:	linux-iio-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
+Description: 	The value of the shunt resistor used to compute power drain on
+                common input voltage pin (RS+). In micro Ohms.
+
+What:		/sys/bus/iio/devices/iio:deviceX/in_current_shunt_resistor
+Date:		March 2017
+KernelVersion:	4.12
+Contact:	linux-iio-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
+Description: 	The value of the shunt resistor used to compute current flowing
+                between RS+ and RS- voltage sense inputs. In micro Ohms.
+
+These attributes describe a single physical component, exposed as two distinct
+attributes as it is used to calculate two different values: power load and
+current flowing between RS+ and RS- inputs.
-- 
2.7.4

[PATCH v4 2/4] iio: Documentation: Add max9611 sysfs documentation

[Jacopo Mondi]

Add documentation for max9611 driver.
Document attributes describing value of shunt resistor installed between
RS+ and RS- voltage sense inputs.

Signed-off-by: Jacopo Mondi <jacopo+renesas@jmondi.org>
---
 Documentation/ABI/testing/sysfs-bus-iio-adc-max9611 | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)
 create mode 100644 Documentation/ABI/testing/sysfs-bus-iio-adc-max9611

diff --git a/Documentation/ABI/testing/sysfs-bus-iio-adc-max9611 b/Documentation/ABI/testing/sysfs-bus-iio-adc-max9611
new file mode 100644
index 0000000..5020d00
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-bus-iio-adc-max9611
@@ -0,0 +1,17 @@
+What:		/sys/bus/iio/devices/iio:deviceX/in_power_shunt_resistor
+Date:		March 2017
+KernelVersion:	4.12
+Contact:	linux-iio@vger.kernel.org
+Description: 	The value of the shunt resistor used to compute power drain on
+                common input voltage pin (RS+). In micro Ohms.
+
+What:		/sys/bus/iio/devices/iio:deviceX/in_current_shunt_resistor
+Date:		March 2017
+KernelVersion:	4.12
+Contact:	linux-iio@vger.kernel.org
+Description: 	The value of the shunt resistor used to compute current flowing
+                between RS+ and RS- voltage sense inputs. In micro Ohms.
+
+These attributes describe a single physical component, exposed as two distinct
+attributes as it is used to calculate two different values: power load and
+current flowing between RS+ and RS- inputs.
-- 
2.7.4

[PATCH v4 3/4] iio: adc: Add Maxim max9611 ADC driver

[Jacopo Mondi]

Add iio driver for Maxim max9611 and max9612 current-sense amplifiers
with 12-bits ADC interface.

Datasheet publicly available at:
https://datasheets.maximintegrated.com/en/ds/MAX9611-MAX9612.pdf

Signed-off-by: Jacopo Mondi <jacopo+renesas-AW8dsiIh9cEdnm+yROfE0A@public.gmane.org>

---

Output of iio_info on Salvator-X board for max9611 chip installed on
VDD_0.8 lines.
The VDD_0.8 line powers the CPU cluster and on-board RAM.

        iio:device0: max9611
                5 channels found:
                        voltage0:  (input)
                        1 channel-specific attributes found:
                                attr 0: input value: 4.085000000
                        voltage1:  (input)
                        3 channel-specific attributes found:
                                attr 0: scale value: 14
                                attr 1: offset value: 1
                                attr 2: raw value: 59
                        power:  (input)
                        2 channel-specific attributes found:
                                attr 0: shunt_resistor value: 5000
                                attr 1: input value: 663.404000000
                        current:  (input)
                        2 channel-specific attributes found:
                                attr 0: shunt_resistor value: 5000
                                attr 1: input value: 817.000000000
                        temp:  (input)
                        2 channel-specific attributes found:
                                attr 0: scale value: 480.076812289
                                attr 1: raw value: 57

The collected information represent:

* voltage0 (current sense voltage) Vcsa
  voltage drop between RS+ and RS- input = 4,085 mV
* voltage1: (common input voltage) Vcim
  voltage at RS+ input = (59 - 1) * 14 = 812 mV
* current flowing on shunt resistor (Icsa)
  = Vcsa / Rshunt = 817 mA
* power load on the sensed line (Pload)
  = Vcim * Icsa = 663 m
* die temperature = (57 * 480.07) = 27360 milli Celsius
---
 drivers/iio/adc/Kconfig   |  10 +
 drivers/iio/adc/Makefile  |   1 +
 drivers/iio/adc/max9611.c | 583 ++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 594 insertions(+)
 create mode 100644 drivers/iio/adc/max9611.c

diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
index dedae7a..82f2e7b8 100644
--- a/drivers/iio/adc/Kconfig
+++ b/drivers/iio/adc/Kconfig
@@ -354,6 +354,16 @@ config MAX1363
 	  To compile this driver as a module, choose M here: the module will be
 	  called max1363.
 
+config	MAX9611
+	tristate "Maxim max9611/max9612 ADC driver"
+	depends on I2C
+	help
+	  Say yes here to build support for Maxim max9611/max9612 current sense
+	  amplifier with 12-bits ADC interface.
+
+	  To compile this driver as a module, choose M here: the module will be
+	  called max9611.
+
 config MCP320X
 	tristate "Microchip Technology MCP3x01/02/04/08"
 	depends on SPI
diff --git a/drivers/iio/adc/Makefile b/drivers/iio/adc/Makefile
index d001262..149f979 100644
--- a/drivers/iio/adc/Makefile
+++ b/drivers/iio/adc/Makefile
@@ -34,6 +34,7 @@ obj-$(CONFIG_LTC2485) += ltc2485.o
 obj-$(CONFIG_MAX1027) += max1027.o
 obj-$(CONFIG_MAX11100) += max11100.o
 obj-$(CONFIG_MAX1363) += max1363.o
+obj-$(CONFIG_MAX9611) += max9611.o
 obj-$(CONFIG_MCP320X) += mcp320x.o
 obj-$(CONFIG_MCP3422) += mcp3422.o
 obj-$(CONFIG_MEDIATEK_MT6577_AUXADC) += mt6577_auxadc.o
diff --git a/drivers/iio/adc/max9611.c b/drivers/iio/adc/max9611.c
new file mode 100644
index 0000000..e5aaf73
--- /dev/null
+++ b/drivers/iio/adc/max9611.c
@@ -0,0 +1,583 @@
+/*
+ * iio/adc/max9611.c
+ *
+ * Maxim max9611/max9612 high side current sense amplifier with
+ * 12-bit ADC interface.
+ *
+ * Copyright (C) 2017 Jacopo Mondi
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+/*
+ * This driver supports input common-mode voltage, current-sense
+ * amplifier with programmable gains and die temperature reading from
+ * Maxim max9611/max9612.
+ *
+ * Op-amp, analog comparator, and watchdog functionalities are not
+ * supported by this driver.
+ */
+
+#include <linux/delay.h>
+#include <linux/i2c.h>
+#include <linux/iio/iio.h>
+#include <linux/iio/sysfs.h>
+#include <linux/module.h>
+#include <linux/of_device.h>
+
+#define DRIVER_NAME 			"max9611"
+#define MAX9611_DEV_NAME		"max9611"
+#define MAX9612_DEV_NAME		"max9612"
+
+/* max9611 register addresses */
+#define MAX9611_REG_CSA_DATA		0x00
+#define MAX9611_REG_RS_DATA		0x02
+#define MAX9611_REG_TEMP_DATA		0x08
+#define MAX9611_REG_CTRL1		0x0a
+#define MAX9611_REG_CTRL2		0x0b
+
+/* max9611 REG1 mux configuration options */
+#define MAX9611_MUX_MASK		GENMASK(3,0)
+#define MAX9611_MUX_SENSE_1x		0x00
+#define MAX9611_MUX_SENSE_4x		0x01
+#define MAX9611_MUX_SENSE_8x		0x02
+#define MAX9611_INPUT_VOLT		0x03
+#define MAX9611_MUX_TEMP		0x06
+
+/* max9611 voltage (both csa and input) helper macros */
+#define MAX9611_VOLTAGE_SHIFT		0x04
+#define MAX9611_VOLTAGE_RAW(_r)		((_r) >> MAX9611_VOLTAGE_SHIFT)
+
+/*
+ * max9611 current sense amplifier voltage output:
+ * LSB and offset values depends on selected gain (1x, 4x, 8x)
+ *
+ * GAIN		LSB (nV)	OFFSET (LSB steps)
+ * 1x		107500		1
+ * 4x		26880		1
+ * 8x		13440		3
+ *
+ * The complete formula to calculate current sense voltage is:
+ *     (((adc_read >> 4) - offset) / ((1 / LSB) * 10^-3)
+ */
+#define MAX9611_CSA_1X_LSB_nV		107500
+#define MAX9611_CSA_4X_LSB_nV		26880
+#define MAX9611_CSA_8X_LSB_nV		13440
+
+#define MAX9611_CSA_1X_OFFS_RAW		1
+#define MAX9611_CSA_4X_OFFS_RAW		1
+#define MAX9611_CSA_8X_OFFS_RAW		3
+
+/*
+ * max9611 common input mode (CIM): LSB is 14mV, with 14mV offset at 25 C
+ *
+ * The complete formula to calculate input common voltage is:
+ *     (((adc_read >> 4) * 1000) - offset) / (1 / 14 * 1000)
+ */
+#define MAX9611_CIM_LSB_mV		14
+#define MAX9611_CIM_OFFSET_RAW		1
+
+/*
+ * max9611 temperature reading: LSB is 480 milli degrees Celsius
+ *
+ * The complete formula to calculate temperature is:
+ *     ((adc_read >> 7) * 1000) / (1 / 480 * 1000)
+ */
+#define MAX9611_TEMP_MAX_POS		0x7f80
+#define MAX9611_TEMP_MAX_NEG		0xff80
+#define MAX9611_TEMP_MIN_NEG		0xd980
+#define MAX9611_TEMP_MASK		GENMASK(7, 15)
+#define MAX9611_TEMP_SHIFT		0x07
+#define MAX9611_TEMP_RAW(_r)		((_r) >> MAX9611_TEMP_SHIFT)
+#define MAX9611_TEMP_SCALE_NUM		1000000
+#define MAX9611_TEMP_SCALE_DIV		2083
+
+struct max9611_dev {
+	struct device *dev;
+	struct i2c_client *i2c_client;
+	struct mutex lock;
+	unsigned int shunt_resistor_uohm;
+};
+
+enum max9611_conf_ids {
+	CONF_SENSE_1x,
+	CONF_SENSE_4x,
+	CONF_SENSE_8x,
+	CONF_IN_VOLT,
+	CONF_TEMP,
+};
+
+/**
+ * max9611_mux_conf - associate ADC mux configuration with register address
+ *		      where data shall be read from
+ */
+static const unsigned int max9611_mux_conf[][2] = {
+	/* CONF_SENSE_1x */
+	{ MAX9611_MUX_SENSE_1x, MAX9611_REG_CSA_DATA },
+	/* CONF_SENSE_4x */
+	{ MAX9611_MUX_SENSE_4x, MAX9611_REG_CSA_DATA },
+	/* CONF_SENSE_8x */
+	{ MAX9611_MUX_SENSE_8x, MAX9611_REG_CSA_DATA },
+	/* CONF_IN_VOLT */
+	{ MAX9611_INPUT_VOLT, MAX9611_REG_RS_DATA },
+	/* CONF_TEMP */
+	{ MAX9611_MUX_TEMP, MAX9611_REG_TEMP_DATA },
+};
+
+enum max9611_csa_gain {
+	CSA_GAIN_1x,
+	CSA_GAIN_4x,
+	CSA_GAIN_8x,
+};
+
+enum max9611_csa_gain_params {
+	CSA_GAIN_LSB_nV,
+	CSA_GAIN_OFFS_RAW,
+};
+
+/**
+ * max9611_csa_gain_conf - associate gain multiplier with LSB and
+ *			   offset values.
+ *
+ * Group together parameters associated with configurable gain
+ * on current sense amplifier path to ADC interface.
+ * Current sense read routine adjusts gain until it gets a meaningful
+ * value; use this structure to retrieve the correct LSB and offset values.
+ */
+static const unsigned int max9611_gain_conf[][2] = {
+	{ /* [0] CSA_GAIN_1x */
+		MAX9611_CSA_1X_LSB_nV,
+		MAX9611_CSA_1X_OFFS_RAW,
+	},
+	{ /* [1] CSA_GAIN_4x */
+		MAX9611_CSA_4X_LSB_nV,
+		MAX9611_CSA_4X_OFFS_RAW,
+	},
+	{ /* [2] CSA_GAIN_8x */
+		MAX9611_CSA_8X_LSB_nV,
+		MAX9611_CSA_8X_OFFS_RAW,
+	},
+};
+
+enum max9611_chan_addrs {
+	MAX9611_CHAN_VOLTAGE_INPUT,
+	MAX9611_CHAN_VOLTAGE_SENSE,
+	MAX9611_CHAN_TEMPERATURE,
+	MAX9611_CHAN_CURRENT_LOAD,
+	MAX9611_CHAN_POWER_LOAD,
+};
+
+static const struct iio_chan_spec max9611_channels[] = {
+	{
+	  .type			= IIO_TEMP,
+	  .info_mask_separate	= BIT(IIO_CHAN_INFO_RAW) |
+				  BIT(IIO_CHAN_INFO_SCALE),
+	  .address		= MAX9611_CHAN_TEMPERATURE,
+	},
+	{
+	  .type			= IIO_VOLTAGE,
+	  .info_mask_separate	= BIT(IIO_CHAN_INFO_PROCESSED),
+	  .address		= MAX9611_CHAN_VOLTAGE_SENSE,
+	  .indexed		= 1,
+	  .channel		= 0,
+	},
+	{
+	  .type			= IIO_VOLTAGE,
+	  .info_mask_separate	= BIT(IIO_CHAN_INFO_RAW)   |
+				  BIT(IIO_CHAN_INFO_SCALE) |
+				  BIT(IIO_CHAN_INFO_OFFSET),
+	  .address		= MAX9611_CHAN_VOLTAGE_INPUT,
+	  .indexed		= 1,
+	  .channel		= 1,
+	},
+	{
+	  .type			= IIO_CURRENT,
+	  .info_mask_separate	= BIT(IIO_CHAN_INFO_PROCESSED),
+	  .address		= MAX9611_CHAN_CURRENT_LOAD,
+	},
+	{
+	  .type			= IIO_POWER,
+	  .info_mask_separate	= BIT(IIO_CHAN_INFO_PROCESSED),
+	  .address		= MAX9611_CHAN_POWER_LOAD
+	},
+};
+
+/**
+ * max9611_read_single() - read a single value from ADC interface
+ *
+ * Data registers are 16 bit long, spread between two 8 bit registers
+ * with consecutive addresses.
+ * Configure ADC mux first, then read register at address "reg_addr".
+ * The smbus_read_word routine asks for 16 bits and the ADC is kind enough
+ * to return values from "reg_addr" and "reg_addr + 1" consecutively.
+ * Data are transmitted with big-endian ordering: MSB arrives first.
+ *
+ * @max9611: max9611 device
+ * @selector: index for mux and register configuration
+ * @raw_val: the value returned from ADC
+ */
+static int max9611_read_single(struct max9611_dev *max9611,
+			       enum max9611_conf_ids selector,
+			       u16 *raw_val)
+{
+	int ret;
+
+	u8 mux_conf = max9611_mux_conf[selector][0] & MAX9611_MUX_MASK;
+	u8 reg_addr = max9611_mux_conf[selector][1];
+
+	/*
+	 * Keep mutex lock held during read-write to avoid mux register
+	 * (CTRL1) re-configuration.
+	 */
+	mutex_lock(&max9611->lock);
+	ret = i2c_smbus_write_byte_data(max9611->i2c_client,
+					MAX9611_REG_CTRL1, mux_conf);
+	if (ret) {
+		dev_err(max9611->dev, "i2c write byte failed: 0x%2x - 0x%2x\n",
+			MAX9611_REG_CTRL1, mux_conf);
+		mutex_unlock(&max9611->lock);
+		return ret;
+	}
+
+	/*
+	 * need a delay here to make register configuration
+	 * stabilize. 1 msec at least, from empirical testing.
+	 */
+	usleep_range(1000, 2000);
+
+	ret = i2c_smbus_read_word_swapped(max9611->i2c_client, reg_addr);
+	if (ret < 0) {
+		dev_err(max9611->dev, "i2c read word from 0x%2x failed\n",
+			reg_addr);
+		mutex_unlock(&max9611->lock);
+		return ret;
+	}
+
+	*raw_val = ret;
+	mutex_unlock(&max9611->lock);
+
+	return 0;
+}
+
+/**
+ * max9611_read_csa_voltage() - read current sense amplifier output voltage
+ *
+ * Current sense amplifier output voltage is read through a configurable
+ * 1x, 4x or 8x gain.
+ * Start with plain 1x gain, and adjust gain control properly until a
+ * meaningful value is read from ADC output.
+ *
+ * @max9611: max9611 device
+ * @adc_raw: raw value read from ADC output
+ * @csa_gain: gain configuration option selector
+ */
+static int max9611_read_csa_voltage(struct max9611_dev *max9611,
+				    u16 *adc_raw,
+				    enum max9611_csa_gain *csa_gain)
+{
+	enum max9611_conf_ids gain_selectors[] = {
+		CONF_SENSE_1x,
+		CONF_SENSE_4x,
+		CONF_SENSE_8x
+	};
+	unsigned int i;
+	int ret;
+
+	for (i = 0; i < ARRAY_SIZE(gain_selectors); ++i) {
+		ret = max9611_read_single(max9611, gain_selectors[i], adc_raw);
+		if (ret)
+			return ret;
+
+		if (*adc_raw > 0) {
+			*csa_gain = gain_selectors[i];
+			return 0;
+		}
+	}
+
+	return -EIO;
+}
+
+static int max9611_read_raw(struct iio_dev *indio_dev,
+			    struct iio_chan_spec const *chan,
+			    int *val, int *val2, long mask)
+{
+	struct max9611_dev *dev = iio_priv(indio_dev);
+	enum max9611_csa_gain gain_selector;
+	const unsigned int *csa_gain;
+	u16 adc_data;
+	int ret;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW:
+
+		switch (chan->address) {
+		case MAX9611_CHAN_TEMPERATURE:
+			ret = max9611_read_single(dev, CONF_TEMP,
+						  &adc_data);
+			if (ret)
+				return -EINVAL;
+
+			*val = MAX9611_TEMP_RAW(adc_data);
+			return IIO_VAL_INT;
+
+		case MAX9611_CHAN_VOLTAGE_INPUT:
+			ret = max9611_read_single(dev, CONF_IN_VOLT,
+						  &adc_data);
+			if (ret)
+				return -EINVAL;
+
+			*val = MAX9611_VOLTAGE_RAW(adc_data);
+			return IIO_VAL_INT;
+		}
+
+		break;
+
+	case IIO_CHAN_INFO_OFFSET:
+		/* MAX9611_CHAN_VOLTAGE_INPUT */
+		*val = MAX9611_CIM_OFFSET_RAW;
+
+		return IIO_VAL_INT;
+
+	case IIO_CHAN_INFO_SCALE:
+
+		switch (chan->address) {
+		case MAX9611_CHAN_TEMPERATURE:
+			*val = MAX9611_TEMP_SCALE_NUM;
+			*val2 = MAX9611_TEMP_SCALE_DIV;
+
+			return IIO_VAL_FRACTIONAL;
+
+		case MAX9611_CHAN_VOLTAGE_INPUT:
+			*val = MAX9611_CIM_LSB_mV;
+
+			return IIO_VAL_INT;
+		}
+
+		break;
+
+	case IIO_CHAN_INFO_PROCESSED:
+
+		switch (chan->address) {
+		case MAX9611_CHAN_VOLTAGE_SENSE:
+			/*
+			 * processed (mV): (raw - offset) * LSB (nV) / 10^6
+			 *
+			 * Even if max9611 can output raw csa voltage readings,
+			 * use a produced value as scale depends on gain.
+			 */
+			ret = max9611_read_csa_voltage(dev, &adc_data,
+						       &gain_selector);
+			if (ret)
+				return -EINVAL;
+
+			csa_gain = max9611_gain_conf[gain_selector];
+
+			adc_data -= csa_gain[CSA_GAIN_OFFS_RAW];
+			*val = MAX9611_VOLTAGE_RAW(adc_data) *
+			       csa_gain[CSA_GAIN_LSB_nV];
+			*val2 = 1000000;
+
+			return IIO_VAL_FRACTIONAL;
+
+		case MAX9611_CHAN_CURRENT_LOAD:
+			/* processed (mA): Vcsa (nV) / Rshunt (uOhm)  */
+			ret = max9611_read_csa_voltage(dev, &adc_data,
+						       &gain_selector);
+			if (ret)
+				return -EINVAL;
+
+			csa_gain = max9611_gain_conf[gain_selector];
+
+			adc_data -= csa_gain[CSA_GAIN_OFFS_RAW];
+			*val = MAX9611_VOLTAGE_RAW(adc_data) *
+			       csa_gain[CSA_GAIN_LSB_nV];
+			*val2 = dev->shunt_resistor_uohm;
+
+			return IIO_VAL_FRACTIONAL;
+
+		case MAX9611_CHAN_POWER_LOAD:
+			/*
+			 * processed (mW): Vin (mV) * Vcsa (uV) /
+			 *		   Rshunt (uOhm)
+			 */
+			ret = max9611_read_single(dev, CONF_IN_VOLT,
+						  &adc_data);
+			if (ret)
+				return -EINVAL;
+
+			adc_data -= MAX9611_CIM_OFFSET_RAW;
+			*val = MAX9611_VOLTAGE_RAW(adc_data) *
+			       MAX9611_CIM_LSB_mV;
+
+			ret = max9611_read_csa_voltage(dev, &adc_data,
+						       &gain_selector);
+			if (ret)
+				return -EINVAL;
+
+			csa_gain = max9611_gain_conf[gain_selector];
+
+			/* divide by 10^3 here to avoid 32bit overflow */
+			adc_data -= csa_gain[CSA_GAIN_OFFS_RAW];
+			*val *= MAX9611_VOLTAGE_RAW(adc_data) *
+				csa_gain[CSA_GAIN_LSB_nV] / 1000;
+			*val2 = dev->shunt_resistor_uohm;
+
+			return IIO_VAL_FRACTIONAL;
+		}
+
+		break;
+	}
+
+	return -EINVAL;
+}
+
+static ssize_t max9611_shunt_resistor_show(struct device *dev,
+					   struct device_attribute *attr,
+					   char *buf)
+{
+	struct max9611_dev *max9611 = iio_priv(dev_to_iio_dev(dev));
+
+	return sprintf(buf, "%u\n", max9611->shunt_resistor_uohm);
+}
+
+static IIO_DEVICE_ATTR(in_power_shunt_resistor, 0444,
+		       max9611_shunt_resistor_show, NULL, 0);
+static IIO_DEVICE_ATTR(in_current_shunt_resistor, 0444,
+		       max9611_shunt_resistor_show, NULL, 0);
+
+static struct attribute *max9611_attributes[] = {
+	&iio_dev_attr_in_power_shunt_resistor.dev_attr.attr,
+	&iio_dev_attr_in_current_shunt_resistor.dev_attr.attr,
+	NULL,
+};
+
+static const struct attribute_group max9611_attribute_group = {
+	.attrs = max9611_attributes,
+};
+
+static const struct iio_info indio_info = {
+	.driver_module	= THIS_MODULE,
+	.read_raw	= max9611_read_raw,
+	.attrs		= &max9611_attribute_group,
+};
+
+static int max9611_init(struct max9611_dev *max9611)
+{
+	struct i2c_client *client = max9611->i2c_client;
+	u16 regval;
+	int ret;
+
+	if (!i2c_check_functionality(client->adapter,
+				     I2C_FUNC_SMBUS_WRITE_BYTE	|
+				     I2C_FUNC_SMBUS_READ_WORD_DATA)) {
+		dev_err(max9611->dev,
+			"I2c adapter does not support smbus write_byte or read_word functionalities: aborting probe.\n");
+		return -EINVAL;
+	}
+
+	/* Make sure die temperature is in range to test communications. */
+	ret = max9611_read_single(max9611, CONF_TEMP, &regval);
+	if (ret)
+		return ret;
+
+	regval = ret & MAX9611_TEMP_MASK;
+
+	if ((regval > MAX9611_TEMP_MAX_POS &&
+	     regval < MAX9611_TEMP_MIN_NEG) ||
+	     regval > MAX9611_TEMP_MAX_NEG) {
+		dev_err(max9611->dev,
+			"Invalid value received from ADC 0x%4x: aborting\n",
+			regval);
+		return -EIO;
+	}
+
+	/* Mux shall be zeroed back before applying other configurations */
+	ret = i2c_smbus_write_byte_data(max9611->i2c_client,
+					MAX9611_REG_CTRL1, 0);
+	if (ret) {
+		dev_err(max9611->dev, "i2c write byte failed: 0x%2x - 0x%2x\n",
+			MAX9611_REG_CTRL1, 0);
+		return ret;
+	}
+
+	ret = i2c_smbus_write_byte_data(max9611->i2c_client,
+					MAX9611_REG_CTRL2, 0);
+	if (ret) {
+		dev_err(max9611->dev, "i2c write byte failed: 0x%2x - 0x%2x\n",
+			MAX9611_REG_CTRL2, 0);
+		return ret;
+	}
+	usleep_range(1000, 2000);
+
+	return 0;
+}
+
+static const struct of_device_id max9611_of_table[] = {
+	{.compatible = "maxim,max9611", .data = MAX9611_DEV_NAME},
+	{.compatible = "maxim,max9612", .data = MAX9612_DEV_NAME},
+	{ },
+};
+
+MODULE_DEVICE_TABLE(of, max9611_of_table);
+static int max9611_probe(struct i2c_client *client,
+			 const struct i2c_device_id *id)
+{
+	const char * const shunt_res_prop = "shunt-resistor-uohm";
+	const struct device_node *of_node = client->dev.of_node;
+	const struct of_device_id *of_id =
+		of_match_device(max9611_of_table, &client->dev);
+	struct max9611_dev *max9611;
+	struct iio_dev *indio_dev;
+	unsigned int of_shunt;
+	int ret;
+
+	indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*max9611));
+	if (IS_ERR(indio_dev))
+		return PTR_ERR(indio_dev);
+
+	i2c_set_clientdata(client, indio_dev);
+
+	max9611			= iio_priv(indio_dev);
+	max9611->dev		= &client->dev;
+	max9611->i2c_client	= client;
+	mutex_init(&max9611->lock);
+
+	ret = of_property_read_u32(of_node, shunt_res_prop, &of_shunt);
+	if (ret) {
+		dev_err(&client->dev,
+			"Missing %s property for %s node\n",
+			shunt_res_prop, of_node->full_name);
+		return ret;
+	}
+	max9611->shunt_resistor_uohm = of_shunt;
+
+	ret = max9611_init(max9611);
+	if (ret)
+		return ret;
+
+	indio_dev->dev.parent	= &client->dev;
+	indio_dev->dev.of_node	= client->dev.of_node;
+	indio_dev->name		= of_id->data;
+	indio_dev->modes	= INDIO_DIRECT_MODE;
+	indio_dev->info		= &indio_info;
+	indio_dev->channels	= max9611_channels;
+	indio_dev->num_channels	= ARRAY_SIZE(max9611_channels);
+
+	return devm_iio_device_register(&client->dev, indio_dev);
+}
+
+static struct i2c_driver max9611_driver = {
+	.driver = {
+		   .name = DRIVER_NAME,
+		   .owner = THIS_MODULE,
+		   .of_match_table = max9611_of_table,
+	},
+	.probe = max9611_probe,
+};
+module_i2c_driver(max9611_driver);
+
+MODULE_AUTHOR("Jacopo Mondi <jacopo+renesas-AW8dsiIh9cEdnm+yROfE0A@public.gmane.org>");
+MODULE_DESCRIPTION("Maxim max9611/12 current sense amplifier with 12bit ADC");
+MODULE_LICENSE("GPL v2");
-- 
2.7.4

[PATCH v4 3/4] iio: adc: Add Maxim max9611 ADC driver

[Jacopo Mondi]

Add iio driver for Maxim max9611 and max9612 current-sense amplifiers
with 12-bits ADC interface.

Datasheet publicly available at:
https://datasheets.maximintegrated.com/en/ds/MAX9611-MAX9612.pdf

Signed-off-by: Jacopo Mondi <jacopo+renesas@jmondi.org>

---

Output of iio_info on Salvator-X board for max9611 chip installed on
VDD_0.8 lines.
The VDD_0.8 line powers the CPU cluster and on-board RAM.

        iio:device0: max9611
                5 channels found:
                        voltage0:  (input)
                        1 channel-specific attributes found:
                                attr 0: input value: 4.085000000
                        voltage1:  (input)
                        3 channel-specific attributes found:
                                attr 0: scale value: 14
                                attr 1: offset value: 1
                                attr 2: raw value: 59
                        power:  (input)
                        2 channel-specific attributes found:
                                attr 0: shunt_resistor value: 5000
                                attr 1: input value: 663.404000000
                        current:  (input)
                        2 channel-specific attributes found:
                                attr 0: shunt_resistor value: 5000
                                attr 1: input value: 817.000000000
                        temp:  (input)
                        2 channel-specific attributes found:
                                attr 0: scale value: 480.076812289
                                attr 1: raw value: 57

The collected information represent:

* voltage0 (current sense voltage) Vcsa
  voltage drop between RS+ and RS- input = 4,085 mV
* voltage1: (common input voltage) Vcim
  voltage at RS+ input = (59 - 1) * 14 = 812 mV
* current flowing on shunt resistor (Icsa)
  = Vcsa / Rshunt = 817 mA
* power load on the sensed line (Pload)
  = Vcim * Icsa = 663 m
* die temperature = (57 * 480.07) = 27360 milli Celsius
---
 drivers/iio/adc/Kconfig   |  10 +
 drivers/iio/adc/Makefile  |   1 +
 drivers/iio/adc/max9611.c | 583 ++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 594 insertions(+)
 create mode 100644 drivers/iio/adc/max9611.c

diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
index dedae7a..82f2e7b8 100644
--- a/drivers/iio/adc/Kconfig
+++ b/drivers/iio/adc/Kconfig
@@ -354,6 +354,16 @@ config MAX1363
 	  To compile this driver as a module, choose M here: the module will be
 	  called max1363.
 
+config	MAX9611
+	tristate "Maxim max9611/max9612 ADC driver"
+	depends on I2C
+	help
+	  Say yes here to build support for Maxim max9611/max9612 current sense
+	  amplifier with 12-bits ADC interface.
+
+	  To compile this driver as a module, choose M here: the module will be
+	  called max9611.
+
 config MCP320X
 	tristate "Microchip Technology MCP3x01/02/04/08"
 	depends on SPI
diff --git a/drivers/iio/adc/Makefile b/drivers/iio/adc/Makefile
index d001262..149f979 100644
--- a/drivers/iio/adc/Makefile
+++ b/drivers/iio/adc/Makefile
@@ -34,6 +34,7 @@ obj-$(CONFIG_LTC2485) += ltc2485.o
 obj-$(CONFIG_MAX1027) += max1027.o
 obj-$(CONFIG_MAX11100) += max11100.o
 obj-$(CONFIG_MAX1363) += max1363.o
+obj-$(CONFIG_MAX9611) += max9611.o
 obj-$(CONFIG_MCP320X) += mcp320x.o
 obj-$(CONFIG_MCP3422) += mcp3422.o
 obj-$(CONFIG_MEDIATEK_MT6577_AUXADC) += mt6577_auxadc.o
diff --git a/drivers/iio/adc/max9611.c b/drivers/iio/adc/max9611.c
new file mode 100644
index 0000000..e5aaf73
--- /dev/null
+++ b/drivers/iio/adc/max9611.c
@@ -0,0 +1,583 @@
+/*
+ * iio/adc/max9611.c
+ *
+ * Maxim max9611/max9612 high side current sense amplifier with
+ * 12-bit ADC interface.
+ *
+ * Copyright (C) 2017 Jacopo Mondi
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+/*
+ * This driver supports input common-mode voltage, current-sense
+ * amplifier with programmable gains and die temperature reading from
+ * Maxim max9611/max9612.
+ *
+ * Op-amp, analog comparator, and watchdog functionalities are not
+ * supported by this driver.
+ */
+
+#include <linux/delay.h>
+#include <linux/i2c.h>
+#include <linux/iio/iio.h>
+#include <linux/iio/sysfs.h>
+#include <linux/module.h>
+#include <linux/of_device.h>
+
+#define DRIVER_NAME 			"max9611"
+#define MAX9611_DEV_NAME		"max9611"
+#define MAX9612_DEV_NAME		"max9612"
+
+/* max9611 register addresses */
+#define MAX9611_REG_CSA_DATA		0x00
+#define MAX9611_REG_RS_DATA		0x02
+#define MAX9611_REG_TEMP_DATA		0x08
+#define MAX9611_REG_CTRL1		0x0a
+#define MAX9611_REG_CTRL2		0x0b
+
+/* max9611 REG1 mux configuration options */
+#define MAX9611_MUX_MASK		GENMASK(3,0)
+#define MAX9611_MUX_SENSE_1x		0x00
+#define MAX9611_MUX_SENSE_4x		0x01
+#define MAX9611_MUX_SENSE_8x		0x02
+#define MAX9611_INPUT_VOLT		0x03
+#define MAX9611_MUX_TEMP		0x06
+
+/* max9611 voltage (both csa and input) helper macros */
+#define MAX9611_VOLTAGE_SHIFT		0x04
+#define MAX9611_VOLTAGE_RAW(_r)		((_r) >> MAX9611_VOLTAGE_SHIFT)
+
+/*
+ * max9611 current sense amplifier voltage output:
+ * LSB and offset values depends on selected gain (1x, 4x, 8x)
+ *
+ * GAIN		LSB (nV)	OFFSET (LSB steps)
+ * 1x		107500		1
+ * 4x		26880		1
+ * 8x		13440		3
+ *
+ * The complete formula to calculate current sense voltage is:
+ *     (((adc_read >> 4) - offset) / ((1 / LSB) * 10^-3)
+ */
+#define MAX9611_CSA_1X_LSB_nV		107500
+#define MAX9611_CSA_4X_LSB_nV		26880
+#define MAX9611_CSA_8X_LSB_nV		13440
+
+#define MAX9611_CSA_1X_OFFS_RAW		1
+#define MAX9611_CSA_4X_OFFS_RAW		1
+#define MAX9611_CSA_8X_OFFS_RAW		3
+
+/*
+ * max9611 common input mode (CIM): LSB is 14mV, with 14mV offset at 25 C
+ *
+ * The complete formula to calculate input common voltage is:
+ *     (((adc_read >> 4) * 1000) - offset) / (1 / 14 * 1000)
+ */
+#define MAX9611_CIM_LSB_mV		14
+#define MAX9611_CIM_OFFSET_RAW		1
+
+/*
+ * max9611 temperature reading: LSB is 480 milli degrees Celsius
+ *
+ * The complete formula to calculate temperature is:
+ *     ((adc_read >> 7) * 1000) / (1 / 480 * 1000)
+ */
+#define MAX9611_TEMP_MAX_POS		0x7f80
+#define MAX9611_TEMP_MAX_NEG		0xff80
+#define MAX9611_TEMP_MIN_NEG		0xd980
+#define MAX9611_TEMP_MASK		GENMASK(7, 15)
+#define MAX9611_TEMP_SHIFT		0x07
+#define MAX9611_TEMP_RAW(_r)		((_r) >> MAX9611_TEMP_SHIFT)
+#define MAX9611_TEMP_SCALE_NUM		1000000
+#define MAX9611_TEMP_SCALE_DIV		2083
+
+struct max9611_dev {
+	struct device *dev;
+	struct i2c_client *i2c_client;
+	struct mutex lock;
+	unsigned int shunt_resistor_uohm;
+};
+
+enum max9611_conf_ids {
+	CONF_SENSE_1x,
+	CONF_SENSE_4x,
+	CONF_SENSE_8x,
+	CONF_IN_VOLT,
+	CONF_TEMP,
+};
+
+/**
+ * max9611_mux_conf - associate ADC mux configuration with register address
+ *		      where data shall be read from
+ */
+static const unsigned int max9611_mux_conf[][2] = {
+	/* CONF_SENSE_1x */
+	{ MAX9611_MUX_SENSE_1x, MAX9611_REG_CSA_DATA },
+	/* CONF_SENSE_4x */
+	{ MAX9611_MUX_SENSE_4x, MAX9611_REG_CSA_DATA },
+	/* CONF_SENSE_8x */
+	{ MAX9611_MUX_SENSE_8x, MAX9611_REG_CSA_DATA },
+	/* CONF_IN_VOLT */
+	{ MAX9611_INPUT_VOLT, MAX9611_REG_RS_DATA },
+	/* CONF_TEMP */
+	{ MAX9611_MUX_TEMP, MAX9611_REG_TEMP_DATA },
+};
+
+enum max9611_csa_gain {
+	CSA_GAIN_1x,
+	CSA_GAIN_4x,
+	CSA_GAIN_8x,
+};
+
+enum max9611_csa_gain_params {
+	CSA_GAIN_LSB_nV,
+	CSA_GAIN_OFFS_RAW,
+};
+
+/**
+ * max9611_csa_gain_conf - associate gain multiplier with LSB and
+ *			   offset values.
+ *
+ * Group together parameters associated with configurable gain
+ * on current sense amplifier path to ADC interface.
+ * Current sense read routine adjusts gain until it gets a meaningful
+ * value; use this structure to retrieve the correct LSB and offset values.
+ */
+static const unsigned int max9611_gain_conf[][2] = {
+	{ /* [0] CSA_GAIN_1x */
+		MAX9611_CSA_1X_LSB_nV,
+		MAX9611_CSA_1X_OFFS_RAW,
+	},
+	{ /* [1] CSA_GAIN_4x */
+		MAX9611_CSA_4X_LSB_nV,
+		MAX9611_CSA_4X_OFFS_RAW,
+	},
+	{ /* [2] CSA_GAIN_8x */
+		MAX9611_CSA_8X_LSB_nV,
+		MAX9611_CSA_8X_OFFS_RAW,
+	},
+};
+
+enum max9611_chan_addrs {
+	MAX9611_CHAN_VOLTAGE_INPUT,
+	MAX9611_CHAN_VOLTAGE_SENSE,
+	MAX9611_CHAN_TEMPERATURE,
+	MAX9611_CHAN_CURRENT_LOAD,
+	MAX9611_CHAN_POWER_LOAD,
+};
+
+static const struct iio_chan_spec max9611_channels[] = {
+	{
+	  .type			= IIO_TEMP,
+	  .info_mask_separate	= BIT(IIO_CHAN_INFO_RAW) |
+				  BIT(IIO_CHAN_INFO_SCALE),
+	  .address		= MAX9611_CHAN_TEMPERATURE,
+	},
+	{
+	  .type			= IIO_VOLTAGE,
+	  .info_mask_separate	= BIT(IIO_CHAN_INFO_PROCESSED),
+	  .address		= MAX9611_CHAN_VOLTAGE_SENSE,
+	  .indexed		= 1,
+	  .channel		= 0,
+	},
+	{
+	  .type			= IIO_VOLTAGE,
+	  .info_mask_separate	= BIT(IIO_CHAN_INFO_RAW)   |
+				  BIT(IIO_CHAN_INFO_SCALE) |
+				  BIT(IIO_CHAN_INFO_OFFSET),
+	  .address		= MAX9611_CHAN_VOLTAGE_INPUT,
+	  .indexed		= 1,
+	  .channel		= 1,
+	},
+	{
+	  .type			= IIO_CURRENT,
+	  .info_mask_separate	= BIT(IIO_CHAN_INFO_PROCESSED),
+	  .address		= MAX9611_CHAN_CURRENT_LOAD,
+	},
+	{
+	  .type			= IIO_POWER,
+	  .info_mask_separate	= BIT(IIO_CHAN_INFO_PROCESSED),
+	  .address		= MAX9611_CHAN_POWER_LOAD
+	},
+};
+
+/**
+ * max9611_read_single() - read a single value from ADC interface
+ *
+ * Data registers are 16 bit long, spread between two 8 bit registers
+ * with consecutive addresses.
+ * Configure ADC mux first, then read register at address "reg_addr".
+ * The smbus_read_word routine asks for 16 bits and the ADC is kind enough
+ * to return values from "reg_addr" and "reg_addr + 1" consecutively.
+ * Data are transmitted with big-endian ordering: MSB arrives first.
+ *
+ * @max9611: max9611 device
+ * @selector: index for mux and register configuration
+ * @raw_val: the value returned from ADC
+ */
+static int max9611_read_single(struct max9611_dev *max9611,
+			       enum max9611_conf_ids selector,
+			       u16 *raw_val)
+{
+	int ret;
+
+	u8 mux_conf = max9611_mux_conf[selector][0] & MAX9611_MUX_MASK;
+	u8 reg_addr = max9611_mux_conf[selector][1];
+
+	/*
+	 * Keep mutex lock held during read-write to avoid mux register
+	 * (CTRL1) re-configuration.
+	 */
+	mutex_lock(&max9611->lock);
+	ret = i2c_smbus_write_byte_data(max9611->i2c_client,
+					MAX9611_REG_CTRL1, mux_conf);
+	if (ret) {
+		dev_err(max9611->dev, "i2c write byte failed: 0x%2x - 0x%2x\n",
+			MAX9611_REG_CTRL1, mux_conf);
+		mutex_unlock(&max9611->lock);
+		return ret;
+	}
+
+	/*
+	 * need a delay here to make register configuration
+	 * stabilize. 1 msec at least, from empirical testing.
+	 */
+	usleep_range(1000, 2000);
+
+	ret = i2c_smbus_read_word_swapped(max9611->i2c_client, reg_addr);
+	if (ret < 0) {
+		dev_err(max9611->dev, "i2c read word from 0x%2x failed\n",
+			reg_addr);
+		mutex_unlock(&max9611->lock);
+		return ret;
+	}
+
+	*raw_val = ret;
+	mutex_unlock(&max9611->lock);
+
+	return 0;
+}
+
+/**
+ * max9611_read_csa_voltage() - read current sense amplifier output voltage
+ *
+ * Current sense amplifier output voltage is read through a configurable
+ * 1x, 4x or 8x gain.
+ * Start with plain 1x gain, and adjust gain control properly until a
+ * meaningful value is read from ADC output.
+ *
+ * @max9611: max9611 device
+ * @adc_raw: raw value read from ADC output
+ * @csa_gain: gain configuration option selector
+ */
+static int max9611_read_csa_voltage(struct max9611_dev *max9611,
+				    u16 *adc_raw,
+				    enum max9611_csa_gain *csa_gain)
+{
+	enum max9611_conf_ids gain_selectors[] = {
+		CONF_SENSE_1x,
+		CONF_SENSE_4x,
+		CONF_SENSE_8x
+	};
+	unsigned int i;
+	int ret;
+
+	for (i = 0; i < ARRAY_SIZE(gain_selectors); ++i) {
+		ret = max9611_read_single(max9611, gain_selectors[i], adc_raw);
+		if (ret)
+			return ret;
+
+		if (*adc_raw > 0) {
+			*csa_gain = gain_selectors[i];
+			return 0;
+		}
+	}
+
+	return -EIO;
+}
+
+static int max9611_read_raw(struct iio_dev *indio_dev,
+			    struct iio_chan_spec const *chan,
+			    int *val, int *val2, long mask)
+{
+	struct max9611_dev *dev = iio_priv(indio_dev);
+	enum max9611_csa_gain gain_selector;
+	const unsigned int *csa_gain;
+	u16 adc_data;
+	int ret;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW:
+
+		switch (chan->address) {
+		case MAX9611_CHAN_TEMPERATURE:
+			ret = max9611_read_single(dev, CONF_TEMP,
+						  &adc_data);
+			if (ret)
+				return -EINVAL;
+
+			*val = MAX9611_TEMP_RAW(adc_data);
+			return IIO_VAL_INT;
+
+		case MAX9611_CHAN_VOLTAGE_INPUT:
+			ret = max9611_read_single(dev, CONF_IN_VOLT,
+						  &adc_data);
+			if (ret)
+				return -EINVAL;
+
+			*val = MAX9611_VOLTAGE_RAW(adc_data);
+			return IIO_VAL_INT;
+		}
+
+		break;
+
+	case IIO_CHAN_INFO_OFFSET:
+		/* MAX9611_CHAN_VOLTAGE_INPUT */
+		*val = MAX9611_CIM_OFFSET_RAW;
+
+		return IIO_VAL_INT;
+
+	case IIO_CHAN_INFO_SCALE:
+
+		switch (chan->address) {
+		case MAX9611_CHAN_TEMPERATURE:
+			*val = MAX9611_TEMP_SCALE_NUM;
+			*val2 = MAX9611_TEMP_SCALE_DIV;
+
+			return IIO_VAL_FRACTIONAL;
+
+		case MAX9611_CHAN_VOLTAGE_INPUT:
+			*val = MAX9611_CIM_LSB_mV;
+
+			return IIO_VAL_INT;
+		}
+
+		break;
+
+	case IIO_CHAN_INFO_PROCESSED:
+
+		switch (chan->address) {
+		case MAX9611_CHAN_VOLTAGE_SENSE:
+			/*
+			 * processed (mV): (raw - offset) * LSB (nV) / 10^6
+			 *
+			 * Even if max9611 can output raw csa voltage readings,
+			 * use a produced value as scale depends on gain.
+			 */
+			ret = max9611_read_csa_voltage(dev, &adc_data,
+						       &gain_selector);
+			if (ret)
+				return -EINVAL;
+
+			csa_gain = max9611_gain_conf[gain_selector];
+
+			adc_data -= csa_gain[CSA_GAIN_OFFS_RAW];
+			*val = MAX9611_VOLTAGE_RAW(adc_data) *
+			       csa_gain[CSA_GAIN_LSB_nV];
+			*val2 = 1000000;
+
+			return IIO_VAL_FRACTIONAL;
+
+		case MAX9611_CHAN_CURRENT_LOAD:
+			/* processed (mA): Vcsa (nV) / Rshunt (uOhm)  */
+			ret = max9611_read_csa_voltage(dev, &adc_data,
+						       &gain_selector);
+			if (ret)
+				return -EINVAL;
+
+			csa_gain = max9611_gain_conf[gain_selector];
+
+			adc_data -= csa_gain[CSA_GAIN_OFFS_RAW];
+			*val = MAX9611_VOLTAGE_RAW(adc_data) *
+			       csa_gain[CSA_GAIN_LSB_nV];
+			*val2 = dev->shunt_resistor_uohm;
+
+			return IIO_VAL_FRACTIONAL;
+
+		case MAX9611_CHAN_POWER_LOAD:
+			/*
+			 * processed (mW): Vin (mV) * Vcsa (uV) /
+			 *		   Rshunt (uOhm)
+			 */
+			ret = max9611_read_single(dev, CONF_IN_VOLT,
+						  &adc_data);
+			if (ret)
+				return -EINVAL;
+
+			adc_data -= MAX9611_CIM_OFFSET_RAW;
+			*val = MAX9611_VOLTAGE_RAW(adc_data) *
+			       MAX9611_CIM_LSB_mV;
+
+			ret = max9611_read_csa_voltage(dev, &adc_data,
+						       &gain_selector);
+			if (ret)
+				return -EINVAL;
+
+			csa_gain = max9611_gain_conf[gain_selector];
+
+			/* divide by 10^3 here to avoid 32bit overflow */
+			adc_data -= csa_gain[CSA_GAIN_OFFS_RAW];
+			*val *= MAX9611_VOLTAGE_RAW(adc_data) *
+				csa_gain[CSA_GAIN_LSB_nV] / 1000;
+			*val2 = dev->shunt_resistor_uohm;
+
+			return IIO_VAL_FRACTIONAL;
+		}
+
+		break;
+	}
+
+	return -EINVAL;
+}
+
+static ssize_t max9611_shunt_resistor_show(struct device *dev,
+					   struct device_attribute *attr,
+					   char *buf)
+{
+	struct max9611_dev *max9611 = iio_priv(dev_to_iio_dev(dev));
+
+	return sprintf(buf, "%u\n", max9611->shunt_resistor_uohm);
+}
+
+static IIO_DEVICE_ATTR(in_power_shunt_resistor, 0444,
+		       max9611_shunt_resistor_show, NULL, 0);
+static IIO_DEVICE_ATTR(in_current_shunt_resistor, 0444,
+		       max9611_shunt_resistor_show, NULL, 0);
+
+static struct attribute *max9611_attributes[] = {
+	&iio_dev_attr_in_power_shunt_resistor.dev_attr.attr,
+	&iio_dev_attr_in_current_shunt_resistor.dev_attr.attr,
+	NULL,
+};
+
+static const struct attribute_group max9611_attribute_group = {
+	.attrs = max9611_attributes,
+};
+
+static const struct iio_info indio_info = {
+	.driver_module	= THIS_MODULE,
+	.read_raw	= max9611_read_raw,
+	.attrs		= &max9611_attribute_group,
+};
+
+static int max9611_init(struct max9611_dev *max9611)
+{
+	struct i2c_client *client = max9611->i2c_client;
+	u16 regval;
+	int ret;
+
+	if (!i2c_check_functionality(client->adapter,
+				     I2C_FUNC_SMBUS_WRITE_BYTE	|
+				     I2C_FUNC_SMBUS_READ_WORD_DATA)) {
+		dev_err(max9611->dev,
+			"I2c adapter does not support smbus write_byte or read_word functionalities: aborting probe.\n");
+		return -EINVAL;
+	}
+
+	/* Make sure die temperature is in range to test communications. */
+	ret = max9611_read_single(max9611, CONF_TEMP, &regval);
+	if (ret)
+		return ret;
+
+	regval = ret & MAX9611_TEMP_MASK;
+
+	if ((regval > MAX9611_TEMP_MAX_POS &&
+	     regval < MAX9611_TEMP_MIN_NEG) ||
+	     regval > MAX9611_TEMP_MAX_NEG) {
+		dev_err(max9611->dev,
+			"Invalid value received from ADC 0x%4x: aborting\n",
+			regval);
+		return -EIO;
+	}
+
+	/* Mux shall be zeroed back before applying other configurations */
+	ret = i2c_smbus_write_byte_data(max9611->i2c_client,
+					MAX9611_REG_CTRL1, 0);
+	if (ret) {
+		dev_err(max9611->dev, "i2c write byte failed: 0x%2x - 0x%2x\n",
+			MAX9611_REG_CTRL1, 0);
+		return ret;
+	}
+
+	ret = i2c_smbus_write_byte_data(max9611->i2c_client,
+					MAX9611_REG_CTRL2, 0);
+	if (ret) {
+		dev_err(max9611->dev, "i2c write byte failed: 0x%2x - 0x%2x\n",
+			MAX9611_REG_CTRL2, 0);
+		return ret;
+	}
+	usleep_range(1000, 2000);
+
+	return 0;
+}
+
+static const struct of_device_id max9611_of_table[] = {
+	{.compatible = "maxim,max9611", .data = MAX9611_DEV_NAME},
+	{.compatible = "maxim,max9612", .data = MAX9612_DEV_NAME},
+	{ },
+};
+
+MODULE_DEVICE_TABLE(of, max9611_of_table);
+static int max9611_probe(struct i2c_client *client,
+			 const struct i2c_device_id *id)
+{
+	const char * const shunt_res_prop = "shunt-resistor-uohm";
+	const struct device_node *of_node = client->dev.of_node;
+	const struct of_device_id *of_id =
+		of_match_device(max9611_of_table, &client->dev);
+	struct max9611_dev *max9611;
+	struct iio_dev *indio_dev;
+	unsigned int of_shunt;
+	int ret;
+
+	indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*max9611));
+	if (IS_ERR(indio_dev))
+		return PTR_ERR(indio_dev);
+
+	i2c_set_clientdata(client, indio_dev);
+
+	max9611			= iio_priv(indio_dev);
+	max9611->dev		= &client->dev;
+	max9611->i2c_client	= client;
+	mutex_init(&max9611->lock);
+
+	ret = of_property_read_u32(of_node, shunt_res_prop, &of_shunt);
+	if (ret) {
+		dev_err(&client->dev,
+			"Missing %s property for %s node\n",
+			shunt_res_prop, of_node->full_name);
+		return ret;
+	}
+	max9611->shunt_resistor_uohm = of_shunt;
+
+	ret = max9611_init(max9611);
+	if (ret)
+		return ret;
+
+	indio_dev->dev.parent	= &client->dev;
+	indio_dev->dev.of_node	= client->dev.of_node;
+	indio_dev->name		= of_id->data;
+	indio_dev->modes	= INDIO_DIRECT_MODE;
+	indio_dev->info		= &indio_info;
+	indio_dev->channels	= max9611_channels;
+	indio_dev->num_channels	= ARRAY_SIZE(max9611_channels);
+
+	return devm_iio_device_register(&client->dev, indio_dev);
+}
+
+static struct i2c_driver max9611_driver = {
+	.driver = {
+		   .name = DRIVER_NAME,
+		   .owner = THIS_MODULE,
+		   .of_match_table = max9611_of_table,
+	},
+	.probe = max9611_probe,
+};
+module_i2c_driver(max9611_driver);
+
+MODULE_AUTHOR("Jacopo Mondi <jacopo+renesas@jmondi.org>");
+MODULE_DESCRIPTION("Maxim max9611/12 current sense amplifier with 12bit ADC");
+MODULE_LICENSE("GPL v2");
-- 
2.7.4

[PATCH v4 4/4] arm64: dts: salvator-x: Add current sense amplifiers

[Jacopo Mondi]

Add device nodes for two Maxim max961x current sense amplifiers
sensing VDD_08 and DVFS_08 lines.

Signed-off-by: Jacopo Mondi <jacopo+renesas@jmondi.org>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
---
 arch/arm64/boot/dts/renesas/r8a7796-salvator-x.dts | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/arch/arm64/boot/dts/renesas/r8a7796-salvator-x.dts b/arch/arm64/boot/dts/renesas/r8a7796-salvator-x.dts
index c7f40f8..389a177 100644
--- a/arch/arm64/boot/dts/renesas/r8a7796-salvator-x.dts
+++ b/arch/arm64/boot/dts/renesas/r8a7796-salvator-x.dts
@@ -257,6 +257,24 @@
 	status = "okay";
 };
 
+&i2c4 {
+	status = "okay";
+
+	csa_vdd: adc@7c {
+		compatible = "maxim,max9611";
+		reg = <0x7c>;
+
+		shunt-resistor-uohm = <5000>;
+	};
+
+	csa_dvfs: adc@7f {
+		compatible = "maxim,max9611";
+		reg = <0x7f>;
+
+		shunt-resistor-uohm = <5000>;
+	};
+};
+
 &wdt0 {
 	timeout-sec = <60>;
 	status = "okay";
-- 
2.7.4

Re: [PATCH v4 1/4] Documentation: dt-bindings: iio: Add max9611 ADC

[Jonathan Cameron]

On 27/03/17 16:12, Jacopo Mondi wrote:
> Add device tree bindings documentation for Maxim max9611/max9612 current
> sense amplifier.
> 
> Signed-off-by: Jacopo Mondi <jacopo+renesas@jmondi.org>
> ---
>  .../devicetree/bindings/iio/adc/max9611.txt        | 26 ++++++++++++++++++++++
>  1 file changed, 26 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/iio/adc/max9611.txt
> 
> diff --git a/Documentation/devicetree/bindings/iio/adc/max9611.txt b/Documentation/devicetree/bindings/iio/adc/max9611.txt
> new file mode 100644
> index 0000000..8430d3b
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/iio/adc/max9611.txt
> @@ -0,0 +1,26 @@
> +* Maxim max9611/max9612 current sense amplifier with 12-bits ADC interface
> +
> +Maxim max9611/max9612 is an high-side current sense amplifier with integrated
> +12-bits ADC communicating over I2c bus.
> +The device node for this driver shall be a child of a I2c controller.
> +
> +Required properties
> +  - compatible: Should be "maxim,max9611" or "maxim,max9612"
> +  - reg: The 7-bits long I2c address of the device
> +  - shunt-resistor-uohm: Value, in uOhm, of the current sense shunt resistor
Just did a quick grep for this see if I felt comfortable enough to
not wait for Rob / Mark to have a chance to look at it.
Grep gave me:
shunt-resistor-micro-ohms for the ina2xx.
Feels rather like we should match that.

Otherwise looks good to me.

Jonathan
> +
> +Example:
> +
> +&i2c4 {
> +	csa: adc@7c {
> +		compatible = "maxim,max9611";
> +		reg = <0x7c>;
> +
> +		shunt-resistor-uohm = <5000>;
> +	};
> +};
> +
> +This device node describes a current sense amplifier sitting on I2c4 bus
> +with address 0x7c (read address is 0xf9, write address is 0xf8).
> +A sense resistor of 0,005 Ohm is installed between RS+ and RS- current-sensing
> +inputs.
> 

Re: [PATCH v4 2/4] iio: Documentation: Add max9611 sysfs documentation

[Jonathan Cameron]

On 27/03/17 16:12, Jacopo Mondi wrote:
> Add documentation for max9611 driver.
> Document attributes describing value of shunt resistor installed between
> RS+ and RS- voltage sense inputs.
> 
> Signed-off-by: Jacopo Mondi <jacopo+renesas@jmondi.org>
Good.  Will pick up once the binding is sorted.

Kick me if I don't!
> ---
>  Documentation/ABI/testing/sysfs-bus-iio-adc-max9611 | 17 +++++++++++++++++
>  1 file changed, 17 insertions(+)
>  create mode 100644 Documentation/ABI/testing/sysfs-bus-iio-adc-max9611
> 
> diff --git a/Documentation/ABI/testing/sysfs-bus-iio-adc-max9611 b/Documentation/ABI/testing/sysfs-bus-iio-adc-max9611
> new file mode 100644
> index 0000000..5020d00
> --- /dev/null
> +++ b/Documentation/ABI/testing/sysfs-bus-iio-adc-max9611
> @@ -0,0 +1,17 @@
> +What:		/sys/bus/iio/devices/iio:deviceX/in_power_shunt_resistor
> +Date:		March 2017
> +KernelVersion:	4.12
> +Contact:	linux-iio@vger.kernel.org
> +Description: 	The value of the shunt resistor used to compute power drain on
> +                common input voltage pin (RS+). In micro Ohms.
> +
> +What:		/sys/bus/iio/devices/iio:deviceX/in_current_shunt_resistor
> +Date:		March 2017
> +KernelVersion:	4.12
> +Contact:	linux-iio@vger.kernel.org
> +Description: 	The value of the shunt resistor used to compute current flowing
> +                between RS+ and RS- voltage sense inputs. In micro Ohms.
> +
> +These attributes describe a single physical component, exposed as two distinct
> +attributes as it is used to calculate two different values: power load and
> +current flowing between RS+ and RS- inputs.
> 

Re: [PATCH v4 3/4] iio: adc: Add Maxim max9611 ADC driver

[Jonathan Cameron]

On 27/03/17 16:12, Jacopo Mondi wrote:
> Add iio driver for Maxim max9611 and max9612 current-sense amplifiers
> with 12-bits ADC interface.
> 
> Datasheet publicly available at:
> https://datasheets.maximintegrated.com/en/ds/MAX9611-MAX9612.pdf
> 
> Signed-off-by: Jacopo Mondi <jacopo+renesas-AW8dsiIh9cEdnm+yROfE0A@public.gmane.org>
>
couple of bits inline.  I'd failed to pick up on the shunt resistor units
before.  To be consistent with the rest of the ABI, those exposed via
sysfs ought to be in ohms.  It's also in ohms in the ina2xx driver.

Thanks,

Jonathan
> ---
> 
> Output of iio_info on Salvator-X board for max9611 chip installed on
> VDD_0.8 lines.
> The VDD_0.8 line powers the CPU cluster and on-board RAM.
> 
>         iio:device0: max9611
>                 5 channels found:
>                         voltage0:  (input)
>                         1 channel-specific attributes found:
>                                 attr 0: input value: 4.085000000
>                         voltage1:  (input)
>                         3 channel-specific attributes found:
>                                 attr 0: scale value: 14
>                                 attr 1: offset value: 1
>                                 attr 2: raw value: 59
>                         power:  (input)
>                         2 channel-specific attributes found:
>                                 attr 0: shunt_resistor value: 5000
>                                 attr 1: input value: 663.404000000
>                         current:  (input)
>                         2 channel-specific attributes found:
>                                 attr 0: shunt_resistor value: 5000
>                                 attr 1: input value: 817.000000000
>                         temp:  (input)
>                         2 channel-specific attributes found:
>                                 attr 0: scale value: 480.076812289
>                                 attr 1: raw value: 57
> 
> The collected information represent:
> 
> * voltage0 (current sense voltage) Vcsa
>   voltage drop between RS+ and RS- input = 4,085 mV
> * voltage1: (common input voltage) Vcim
>   voltage at RS+ input = (59 - 1) * 14 = 812 mV
> * current flowing on shunt resistor (Icsa)
>   = Vcsa / Rshunt = 817 mA
> * power load on the sensed line (Pload)
>   = Vcim * Icsa = 663 m
> * die temperature = (57 * 480.07) = 27360 milli Celsius
> ---
>  drivers/iio/adc/Kconfig   |  10 +
>  drivers/iio/adc/Makefile  |   1 +
>  drivers/iio/adc/max9611.c | 583 ++++++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 594 insertions(+)
>  create mode 100644 drivers/iio/adc/max9611.c
> 
> diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
> index dedae7a..82f2e7b8 100644
> --- a/drivers/iio/adc/Kconfig
> +++ b/drivers/iio/adc/Kconfig
> @@ -354,6 +354,16 @@ config MAX1363
>  	  To compile this driver as a module, choose M here: the module will be
>  	  called max1363.
>  
> +config	MAX9611
> +	tristate "Maxim max9611/max9612 ADC driver"
> +	depends on I2C
> +	help
> +	  Say yes here to build support for Maxim max9611/max9612 current sense
> +	  amplifier with 12-bits ADC interface.
> +
> +	  To compile this driver as a module, choose M here: the module will be
> +	  called max9611.
> +
>  config MCP320X
>  	tristate "Microchip Technology MCP3x01/02/04/08"
>  	depends on SPI
> diff --git a/drivers/iio/adc/Makefile b/drivers/iio/adc/Makefile
> index d001262..149f979 100644
> --- a/drivers/iio/adc/Makefile
> +++ b/drivers/iio/adc/Makefile
> @@ -34,6 +34,7 @@ obj-$(CONFIG_LTC2485) += ltc2485.o
>  obj-$(CONFIG_MAX1027) += max1027.o
>  obj-$(CONFIG_MAX11100) += max11100.o
>  obj-$(CONFIG_MAX1363) += max1363.o
> +obj-$(CONFIG_MAX9611) += max9611.o
>  obj-$(CONFIG_MCP320X) += mcp320x.o
>  obj-$(CONFIG_MCP3422) += mcp3422.o
>  obj-$(CONFIG_MEDIATEK_MT6577_AUXADC) += mt6577_auxadc.o
> diff --git a/drivers/iio/adc/max9611.c b/drivers/iio/adc/max9611.c
> new file mode 100644
> index 0000000..e5aaf73
> --- /dev/null
> +++ b/drivers/iio/adc/max9611.c
> @@ -0,0 +1,583 @@
> +/*
> + * iio/adc/max9611.c
> + *
> + * Maxim max9611/max9612 high side current sense amplifier with
> + * 12-bit ADC interface.
> + *
> + * Copyright (C) 2017 Jacopo Mondi
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + */
> +
> +/*
> + * This driver supports input common-mode voltage, current-sense
> + * amplifier with programmable gains and die temperature reading from
> + * Maxim max9611/max9612.
> + *
> + * Op-amp, analog comparator, and watchdog functionalities are not
> + * supported by this driver.
> + */
> +
> +#include <linux/delay.h>
> +#include <linux/i2c.h>
> +#include <linux/iio/iio.h>
> +#include <linux/iio/sysfs.h>
> +#include <linux/module.h>
> +#include <linux/of_device.h>
> +
> +#define DRIVER_NAME 			"max9611"
> +#define MAX9611_DEV_NAME		"max9611"
> +#define MAX9612_DEV_NAME		"max9612"
Really trivial, but what do these defines give us other than
making the code slightly harder to review?

Just put them inline where they are used.
> +
> +/* max9611 register addresses */
> +#define MAX9611_REG_CSA_DATA		0x00
> +#define MAX9611_REG_RS_DATA		0x02
> +#define MAX9611_REG_TEMP_DATA		0x08
> +#define MAX9611_REG_CTRL1		0x0a
> +#define MAX9611_REG_CTRL2		0x0b
> +
> +/* max9611 REG1 mux configuration options */
> +#define MAX9611_MUX_MASK		GENMASK(3,0)
> +#define MAX9611_MUX_SENSE_1x		0x00
> +#define MAX9611_MUX_SENSE_4x		0x01
> +#define MAX9611_MUX_SENSE_8x		0x02
> +#define MAX9611_INPUT_VOLT		0x03
> +#define MAX9611_MUX_TEMP		0x06
> +
> +/* max9611 voltage (both csa and input) helper macros */
> +#define MAX9611_VOLTAGE_SHIFT		0x04
> +#define MAX9611_VOLTAGE_RAW(_r)		((_r) >> MAX9611_VOLTAGE_SHIFT)
> +
> +/*
> + * max9611 current sense amplifier voltage output:
> + * LSB and offset values depends on selected gain (1x, 4x, 8x)
> + *
> + * GAIN		LSB (nV)	OFFSET (LSB steps)
> + * 1x		107500		1
> + * 4x		26880		1
> + * 8x		13440		3
> + *
> + * The complete formula to calculate current sense voltage is:
> + *     (((adc_read >> 4) - offset) / ((1 / LSB) * 10^-3)
> + */
> +#define MAX9611_CSA_1X_LSB_nV		107500
> +#define MAX9611_CSA_4X_LSB_nV		26880
> +#define MAX9611_CSA_8X_LSB_nV		13440
> +
> +#define MAX9611_CSA_1X_OFFS_RAW		1
> +#define MAX9611_CSA_4X_OFFS_RAW		1
> +#define MAX9611_CSA_8X_OFFS_RAW		3
> +
> +/*
> + * max9611 common input mode (CIM): LSB is 14mV, with 14mV offset at 25 C
> + *
> + * The complete formula to calculate input common voltage is:
> + *     (((adc_read >> 4) * 1000) - offset) / (1 / 14 * 1000)
> + */
> +#define MAX9611_CIM_LSB_mV		14
> +#define MAX9611_CIM_OFFSET_RAW		1
> +
> +/*
> + * max9611 temperature reading: LSB is 480 milli degrees Celsius
> + *
> + * The complete formula to calculate temperature is:
> + *     ((adc_read >> 7) * 1000) / (1 / 480 * 1000)
> + */
> +#define MAX9611_TEMP_MAX_POS		0x7f80
> +#define MAX9611_TEMP_MAX_NEG		0xff80
> +#define MAX9611_TEMP_MIN_NEG		0xd980
> +#define MAX9611_TEMP_MASK		GENMASK(7, 15)
> +#define MAX9611_TEMP_SHIFT		0x07
> +#define MAX9611_TEMP_RAW(_r)		((_r) >> MAX9611_TEMP_SHIFT)
> +#define MAX9611_TEMP_SCALE_NUM		1000000
> +#define MAX9611_TEMP_SCALE_DIV		2083
> +
> +struct max9611_dev {
> +	struct device *dev;
> +	struct i2c_client *i2c_client;
> +	struct mutex lock;
> +	unsigned int shunt_resistor_uohm;
> +};
> +
> +enum max9611_conf_ids {
> +	CONF_SENSE_1x,
> +	CONF_SENSE_4x,
> +	CONF_SENSE_8x,
> +	CONF_IN_VOLT,
> +	CONF_TEMP,
> +};
> +
> +/**
> + * max9611_mux_conf - associate ADC mux configuration with register address
> + *		      where data shall be read from
> + */
> +static const unsigned int max9611_mux_conf[][2] = {
> +	/* CONF_SENSE_1x */
> +	{ MAX9611_MUX_SENSE_1x, MAX9611_REG_CSA_DATA },
> +	/* CONF_SENSE_4x */
> +	{ MAX9611_MUX_SENSE_4x, MAX9611_REG_CSA_DATA },
> +	/* CONF_SENSE_8x */
> +	{ MAX9611_MUX_SENSE_8x, MAX9611_REG_CSA_DATA },
> +	/* CONF_IN_VOLT */
> +	{ MAX9611_INPUT_VOLT, MAX9611_REG_RS_DATA },
> +	/* CONF_TEMP */
> +	{ MAX9611_MUX_TEMP, MAX9611_REG_TEMP_DATA },
> +};
> +
> +enum max9611_csa_gain {
> +	CSA_GAIN_1x,
> +	CSA_GAIN_4x,
> +	CSA_GAIN_8x,
> +};
> +
> +enum max9611_csa_gain_params {
> +	CSA_GAIN_LSB_nV,
> +	CSA_GAIN_OFFS_RAW,
> +};
> +
> +/**
> + * max9611_csa_gain_conf - associate gain multiplier with LSB and
> + *			   offset values.
> + *
> + * Group together parameters associated with configurable gain
> + * on current sense amplifier path to ADC interface.
> + * Current sense read routine adjusts gain until it gets a meaningful
> + * value; use this structure to retrieve the correct LSB and offset values.
> + */
> +static const unsigned int max9611_gain_conf[][2] = {
> +	{ /* [0] CSA_GAIN_1x */
> +		MAX9611_CSA_1X_LSB_nV,
> +		MAX9611_CSA_1X_OFFS_RAW,
> +	},
> +	{ /* [1] CSA_GAIN_4x */
> +		MAX9611_CSA_4X_LSB_nV,
> +		MAX9611_CSA_4X_OFFS_RAW,
> +	},
> +	{ /* [2] CSA_GAIN_8x */
> +		MAX9611_CSA_8X_LSB_nV,
> +		MAX9611_CSA_8X_OFFS_RAW,
> +	},
> +};
> +
> +enum max9611_chan_addrs {
> +	MAX9611_CHAN_VOLTAGE_INPUT,
> +	MAX9611_CHAN_VOLTAGE_SENSE,
> +	MAX9611_CHAN_TEMPERATURE,
> +	MAX9611_CHAN_CURRENT_LOAD,
> +	MAX9611_CHAN_POWER_LOAD,
> +};
> +
> +static const struct iio_chan_spec max9611_channels[] = {
> +	{
> +	  .type			= IIO_TEMP,
> +	  .info_mask_separate	= BIT(IIO_CHAN_INFO_RAW) |
> +				  BIT(IIO_CHAN_INFO_SCALE),
> +	  .address		= MAX9611_CHAN_TEMPERATURE,
> +	},
> +	{
> +	  .type			= IIO_VOLTAGE,
> +	  .info_mask_separate	= BIT(IIO_CHAN_INFO_PROCESSED),
> +	  .address		= MAX9611_CHAN_VOLTAGE_SENSE,
> +	  .indexed		= 1,
> +	  .channel		= 0,
> +	},
> +	{
> +	  .type			= IIO_VOLTAGE,
> +	  .info_mask_separate	= BIT(IIO_CHAN_INFO_RAW)   |
> +				  BIT(IIO_CHAN_INFO_SCALE) |
> +				  BIT(IIO_CHAN_INFO_OFFSET),
> +	  .address		= MAX9611_CHAN_VOLTAGE_INPUT,
> +	  .indexed		= 1,
> +	  .channel		= 1,
> +	},
> +	{
> +	  .type			= IIO_CURRENT,
> +	  .info_mask_separate	= BIT(IIO_CHAN_INFO_PROCESSED),
> +	  .address		= MAX9611_CHAN_CURRENT_LOAD,
> +	},
> +	{
> +	  .type			= IIO_POWER,
> +	  .info_mask_separate	= BIT(IIO_CHAN_INFO_PROCESSED),
> +	  .address		= MAX9611_CHAN_POWER_LOAD
> +	},
> +};
> +
> +/**
> + * max9611_read_single() - read a single value from ADC interface
> + *
> + * Data registers are 16 bit long, spread between two 8 bit registers
> + * with consecutive addresses.
> + * Configure ADC mux first, then read register at address "reg_addr".
> + * The smbus_read_word routine asks for 16 bits and the ADC is kind enough
> + * to return values from "reg_addr" and "reg_addr + 1" consecutively.
> + * Data are transmitted with big-endian ordering: MSB arrives first.
> + *
> + * @max9611: max9611 device
> + * @selector: index for mux and register configuration
> + * @raw_val: the value returned from ADC
> + */
> +static int max9611_read_single(struct max9611_dev *max9611,
> +			       enum max9611_conf_ids selector,
> +			       u16 *raw_val)
> +{
> +	int ret;
> +
> +	u8 mux_conf = max9611_mux_conf[selector][0] & MAX9611_MUX_MASK;
> +	u8 reg_addr = max9611_mux_conf[selector][1];
> +
> +	/*
> +	 * Keep mutex lock held during read-write to avoid mux register
> +	 * (CTRL1) re-configuration.
> +	 */
> +	mutex_lock(&max9611->lock);
> +	ret = i2c_smbus_write_byte_data(max9611->i2c_client,
> +					MAX9611_REG_CTRL1, mux_conf);
> +	if (ret) {
> +		dev_err(max9611->dev, "i2c write byte failed: 0x%2x - 0x%2x\n",
> +			MAX9611_REG_CTRL1, mux_conf);
> +		mutex_unlock(&max9611->lock);
> +		return ret;
> +	}
> +
> +	/*
> +	 * need a delay here to make register configuration
> +	 * stabilize. 1 msec at least, from empirical testing.
> +	 */
> +	usleep_range(1000, 2000);
> +
> +	ret = i2c_smbus_read_word_swapped(max9611->i2c_client, reg_addr);
> +	if (ret < 0) {
> +		dev_err(max9611->dev, "i2c read word from 0x%2x failed\n",
> +			reg_addr);
> +		mutex_unlock(&max9611->lock);
> +		return ret;
> +	}
> +
> +	*raw_val = ret;
> +	mutex_unlock(&max9611->lock);
> +
> +	return 0;
> +}
> +
> +/**
> + * max9611_read_csa_voltage() - read current sense amplifier output voltage
> + *
> + * Current sense amplifier output voltage is read through a configurable
> + * 1x, 4x or 8x gain.
> + * Start with plain 1x gain, and adjust gain control properly until a
> + * meaningful value is read from ADC output.
> + *
> + * @max9611: max9611 device
> + * @adc_raw: raw value read from ADC output
> + * @csa_gain: gain configuration option selector
> + */
> +static int max9611_read_csa_voltage(struct max9611_dev *max9611,
> +				    u16 *adc_raw,
> +				    enum max9611_csa_gain *csa_gain)
> +{
> +	enum max9611_conf_ids gain_selectors[] = {
> +		CONF_SENSE_1x,
> +		CONF_SENSE_4x,
> +		CONF_SENSE_8x
> +	};
> +	unsigned int i;
> +	int ret;
> +
> +	for (i = 0; i < ARRAY_SIZE(gain_selectors); ++i) {
> +		ret = max9611_read_single(max9611, gain_selectors[i], adc_raw);
> +		if (ret)
> +			return ret;
> +
> +		if (*adc_raw > 0) {
> +			*csa_gain = gain_selectors[i];
> +			return 0;
> +		}
> +	}
> +
> +	return -EIO;
> +}
> +
> +static int max9611_read_raw(struct iio_dev *indio_dev,
> +			    struct iio_chan_spec const *chan,
> +			    int *val, int *val2, long mask)
> +{
> +	struct max9611_dev *dev = iio_priv(indio_dev);
> +	enum max9611_csa_gain gain_selector;
> +	const unsigned int *csa_gain;
> +	u16 adc_data;
> +	int ret;
> +
> +	switch (mask) {
> +	case IIO_CHAN_INFO_RAW:
> +
> +		switch (chan->address) {
> +		case MAX9611_CHAN_TEMPERATURE:
> +			ret = max9611_read_single(dev, CONF_TEMP,
> +						  &adc_data);
> +			if (ret)
> +				return -EINVAL;
> +
> +			*val = MAX9611_TEMP_RAW(adc_data);
> +			return IIO_VAL_INT;
> +
> +		case MAX9611_CHAN_VOLTAGE_INPUT:
> +			ret = max9611_read_single(dev, CONF_IN_VOLT,
> +						  &adc_data);
> +			if (ret)
> +				return -EINVAL;
> +
> +			*val = MAX9611_VOLTAGE_RAW(adc_data);
> +			return IIO_VAL_INT;
> +		}
> +
> +		break;
> +
> +	case IIO_CHAN_INFO_OFFSET:
> +		/* MAX9611_CHAN_VOLTAGE_INPUT */
> +		*val = MAX9611_CIM_OFFSET_RAW;
> +
> +		return IIO_VAL_INT;
> +
> +	case IIO_CHAN_INFO_SCALE:
> +
> +		switch (chan->address) {
> +		case MAX9611_CHAN_TEMPERATURE:
> +			*val = MAX9611_TEMP_SCALE_NUM;
> +			*val2 = MAX9611_TEMP_SCALE_DIV;
> +
> +			return IIO_VAL_FRACTIONAL;
> +
> +		case MAX9611_CHAN_VOLTAGE_INPUT:
> +			*val = MAX9611_CIM_LSB_mV;
> +
> +			return IIO_VAL_INT;
> +		}
> +
> +		break;
> +
> +	case IIO_CHAN_INFO_PROCESSED:
> +
> +		switch (chan->address) {
> +		case MAX9611_CHAN_VOLTAGE_SENSE:
> +			/*
> +			 * processed (mV): (raw - offset) * LSB (nV) / 10^6
> +			 *
> +			 * Even if max9611 can output raw csa voltage readings,
> +			 * use a produced value as scale depends on gain.
> +			 */
> +			ret = max9611_read_csa_voltage(dev, &adc_data,
> +						       &gain_selector);
> +			if (ret)
> +				return -EINVAL;
> +
> +			csa_gain = max9611_gain_conf[gain_selector];
> +
> +			adc_data -= csa_gain[CSA_GAIN_OFFS_RAW];
> +			*val = MAX9611_VOLTAGE_RAW(adc_data) *
> +			       csa_gain[CSA_GAIN_LSB_nV];
> +			*val2 = 1000000;
> +
> +			return IIO_VAL_FRACTIONAL;
> +
> +		case MAX9611_CHAN_CURRENT_LOAD:
> +			/* processed (mA): Vcsa (nV) / Rshunt (uOhm)  */
> +			ret = max9611_read_csa_voltage(dev, &adc_data,
> +						       &gain_selector);
> +			if (ret)
> +				return -EINVAL;
> +
> +			csa_gain = max9611_gain_conf[gain_selector];
> +
> +			adc_data -= csa_gain[CSA_GAIN_OFFS_RAW];
> +			*val = MAX9611_VOLTAGE_RAW(adc_data) *
> +			       csa_gain[CSA_GAIN_LSB_nV];
> +			*val2 = dev->shunt_resistor_uohm;
> +
> +			return IIO_VAL_FRACTIONAL;
> +
> +		case MAX9611_CHAN_POWER_LOAD:
> +			/*
> +			 * processed (mW): Vin (mV) * Vcsa (uV) /
> +			 *		   Rshunt (uOhm)
> +			 */
> +			ret = max9611_read_single(dev, CONF_IN_VOLT,
> +						  &adc_data);
> +			if (ret)
> +				return -EINVAL;
> +
> +			adc_data -= MAX9611_CIM_OFFSET_RAW;
> +			*val = MAX9611_VOLTAGE_RAW(adc_data) *
> +			       MAX9611_CIM_LSB_mV;
> +
> +			ret = max9611_read_csa_voltage(dev, &adc_data,
> +						       &gain_selector);
> +			if (ret)
> +				return -EINVAL;
> +
> +			csa_gain = max9611_gain_conf[gain_selector];
> +
> +			/* divide by 10^3 here to avoid 32bit overflow */
> +			adc_data -= csa_gain[CSA_GAIN_OFFS_RAW];
> +			*val *= MAX9611_VOLTAGE_RAW(adc_data) *
> +				csa_gain[CSA_GAIN_LSB_nV] / 1000;
> +			*val2 = dev->shunt_resistor_uohm;
> +
> +			return IIO_VAL_FRACTIONAL;
> +		}
> +
> +		break;
> +	}
> +
> +	return -EINVAL;
> +}
> +
> +static ssize_t max9611_shunt_resistor_show(struct device *dev,
> +					   struct device_attribute *attr,
> +					   char *buf)
> +{
> +	struct max9611_dev *max9611 = iio_priv(dev_to_iio_dev(dev));
> +
> +	return sprintf(buf, "%u\n", max9611->shunt_resistor_uohm);
Oops didn't pick up on this before.  Should really be ohms with
appropriate fixed point arithmetic.

This would match with the use of ohms for DPOT devices that we already
have documented.
> +}
> +
> +static IIO_DEVICE_ATTR(in_power_shunt_resistor, 0444,
> +		       max9611_shunt_resistor_show, NULL, 0);
> +static IIO_DEVICE_ATTR(in_current_shunt_resistor, 0444,
> +		       max9611_shunt_resistor_show, NULL, 0);
> +
> +static struct attribute *max9611_attributes[] = {
> +	&iio_dev_attr_in_power_shunt_resistor.dev_attr.attr,
> +	&iio_dev_attr_in_current_shunt_resistor.dev_attr.attr,
> +	NULL,
> +};
> +
> +static const struct attribute_group max9611_attribute_group = {
> +	.attrs = max9611_attributes,
> +};
> +
> +static const struct iio_info indio_info = {
> +	.driver_module	= THIS_MODULE,
> +	.read_raw	= max9611_read_raw,
> +	.attrs		= &max9611_attribute_group,
> +};
> +
> +static int max9611_init(struct max9611_dev *max9611)
> +{
> +	struct i2c_client *client = max9611->i2c_client;
> +	u16 regval;
> +	int ret;
> +
> +	if (!i2c_check_functionality(client->adapter,
> +				     I2C_FUNC_SMBUS_WRITE_BYTE	|
> +				     I2C_FUNC_SMBUS_READ_WORD_DATA)) {
> +		dev_err(max9611->dev,
> +			"I2c adapter does not support smbus write_byte or read_word functionalities: aborting probe.\n");
> +		return -EINVAL;
> +	}
> +
> +	/* Make sure die temperature is in range to test communications. */
> +	ret = max9611_read_single(max9611, CONF_TEMP, &regval);
> +	if (ret)
> +		return ret;
> +
> +	regval = ret & MAX9611_TEMP_MASK;
> +
> +	if ((regval > MAX9611_TEMP_MAX_POS &&
> +	     regval < MAX9611_TEMP_MIN_NEG) ||
> +	     regval > MAX9611_TEMP_MAX_NEG) {
> +		dev_err(max9611->dev,
> +			"Invalid value received from ADC 0x%4x: aborting\n",
> +			regval);
> +		return -EIO;
> +	}
> +
> +	/* Mux shall be zeroed back before applying other configurations */
> +	ret = i2c_smbus_write_byte_data(max9611->i2c_client,
> +					MAX9611_REG_CTRL1, 0);
> +	if (ret) {
> +		dev_err(max9611->dev, "i2c write byte failed: 0x%2x - 0x%2x\n",
> +			MAX9611_REG_CTRL1, 0);
> +		return ret;
> +	}
> +
> +	ret = i2c_smbus_write_byte_data(max9611->i2c_client,
> +					MAX9611_REG_CTRL2, 0);
> +	if (ret) {
> +		dev_err(max9611->dev, "i2c write byte failed: 0x%2x - 0x%2x\n",
> +			MAX9611_REG_CTRL2, 0);
> +		return ret;
> +	}
> +	usleep_range(1000, 2000);
> +
> +	return 0;
> +}
> +
> +static const struct of_device_id max9611_of_table[] = {
> +	{.compatible = "maxim,max9611", .data = MAX9611_DEV_NAME},
> +	{.compatible = "maxim,max9612", .data = MAX9612_DEV_NAME},
> +	{ },
> +};
> +
> +MODULE_DEVICE_TABLE(of, max9611_of_table);
> +static int max9611_probe(struct i2c_client *client,
> +			 const struct i2c_device_id *id)
> +{
> +	const char * const shunt_res_prop = "shunt-resistor-uohm";
> +	const struct device_node *of_node = client->dev.of_node;
> +	const struct of_device_id *of_id =
> +		of_match_device(max9611_of_table, &client->dev);
> +	struct max9611_dev *max9611;
> +	struct iio_dev *indio_dev;
> +	unsigned int of_shunt;
> +	int ret;
> +
> +	indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*max9611));
> +	if (IS_ERR(indio_dev))
> +		return PTR_ERR(indio_dev);
> +
> +	i2c_set_clientdata(client, indio_dev);
> +
> +	max9611			= iio_priv(indio_dev);
> +	max9611->dev		= &client->dev;
> +	max9611->i2c_client	= client;
> +	mutex_init(&max9611->lock);
> +
> +	ret = of_property_read_u32(of_node, shunt_res_prop, &of_shunt);
> +	if (ret) {
> +		dev_err(&client->dev,
> +			"Missing %s property for %s node\n",
> +			shunt_res_prop, of_node->full_name);
> +		return ret;
> +	}
> +	max9611->shunt_resistor_uohm = of_shunt;
> +
> +	ret = max9611_init(max9611);
> +	if (ret)
> +		return ret;
> +
> +	indio_dev->dev.parent	= &client->dev;
> +	indio_dev->dev.of_node	= client->dev.of_node;
> +	indio_dev->name		= of_id->data;
> +	indio_dev->modes	= INDIO_DIRECT_MODE;
> +	indio_dev->info		= &indio_info;
> +	indio_dev->channels	= max9611_channels;
> +	indio_dev->num_channels	= ARRAY_SIZE(max9611_channels);
> +
> +	return devm_iio_device_register(&client->dev, indio_dev);
> +}
> +
> +static struct i2c_driver max9611_driver = {
> +	.driver = {
> +		   .name = DRIVER_NAME,
> +		   .owner = THIS_MODULE,
> +		   .of_match_table = max9611_of_table,
> +	},
> +	.probe = max9611_probe,
> +};
> +module_i2c_driver(max9611_driver);
> +
> +MODULE_AUTHOR("Jacopo Mondi <jacopo+renesas-AW8dsiIh9cEdnm+yROfE0A@public.gmane.org>");
> +MODULE_DESCRIPTION("Maxim max9611/12 current sense amplifier with 12bit ADC");
> +MODULE_LICENSE("GPL v2");
> 

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Re: [PATCH v4 3/4] iio: adc: Add Maxim max9611 ADC driver

[Jonathan Cameron]

On 27/03/17 16:12, Jacopo Mondi wrote:
> Add iio driver for Maxim max9611 and max9612 current-sense amplifiers
> with 12-bits ADC interface.
> 
> Datasheet publicly available at:
> https://datasheets.maximintegrated.com/en/ds/MAX9611-MAX9612.pdf
> 
> Signed-off-by: Jacopo Mondi <jacopo+renesas@jmondi.org>
>
couple of bits inline.  I'd failed to pick up on the shunt resistor units
before.  To be consistent with the rest of the ABI, those exposed via
sysfs ought to be in ohms.  It's also in ohms in the ina2xx driver.

Thanks,

Jonathan
> ---
> 
> Output of iio_info on Salvator-X board for max9611 chip installed on
> VDD_0.8 lines.
> The VDD_0.8 line powers the CPU cluster and on-board RAM.
> 
>         iio:device0: max9611
>                 5 channels found:
>                         voltage0:  (input)
>                         1 channel-specific attributes found:
>                                 attr 0: input value: 4.085000000
>                         voltage1:  (input)
>                         3 channel-specific attributes found:
>                                 attr 0: scale value: 14
>                                 attr 1: offset value: 1
>                                 attr 2: raw value: 59
>                         power:  (input)
>                         2 channel-specific attributes found:
>                                 attr 0: shunt_resistor value: 5000
>                                 attr 1: input value: 663.404000000
>                         current:  (input)
>                         2 channel-specific attributes found:
>                                 attr 0: shunt_resistor value: 5000
>                                 attr 1: input value: 817.000000000
>                         temp:  (input)
>                         2 channel-specific attributes found:
>                                 attr 0: scale value: 480.076812289
>                                 attr 1: raw value: 57
> 
> The collected information represent:
> 
> * voltage0 (current sense voltage) Vcsa
>   voltage drop between RS+ and RS- input = 4,085 mV
> * voltage1: (common input voltage) Vcim
>   voltage at RS+ input = (59 - 1) * 14 = 812 mV
> * current flowing on shunt resistor (Icsa)
>   = Vcsa / Rshunt = 817 mA
> * power load on the sensed line (Pload)
>   = Vcim * Icsa = 663 m
> * die temperature = (57 * 480.07) = 27360 milli Celsius
> ---
>  drivers/iio/adc/Kconfig   |  10 +
>  drivers/iio/adc/Makefile  |   1 +
>  drivers/iio/adc/max9611.c | 583 ++++++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 594 insertions(+)
>  create mode 100644 drivers/iio/adc/max9611.c
> 
> diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
> index dedae7a..82f2e7b8 100644
> --- a/drivers/iio/adc/Kconfig
> +++ b/drivers/iio/adc/Kconfig
> @@ -354,6 +354,16 @@ config MAX1363
>  	  To compile this driver as a module, choose M here: the module will be
>  	  called max1363.
>  
> +config	MAX9611
> +	tristate "Maxim max9611/max9612 ADC driver"
> +	depends on I2C
> +	help
> +	  Say yes here to build support for Maxim max9611/max9612 current sense
> +	  amplifier with 12-bits ADC interface.
> +
> +	  To compile this driver as a module, choose M here: the module will be
> +	  called max9611.
> +
>  config MCP320X
>  	tristate "Microchip Technology MCP3x01/02/04/08"
>  	depends on SPI
> diff --git a/drivers/iio/adc/Makefile b/drivers/iio/adc/Makefile
> index d001262..149f979 100644
> --- a/drivers/iio/adc/Makefile
> +++ b/drivers/iio/adc/Makefile
> @@ -34,6 +34,7 @@ obj-$(CONFIG_LTC2485) += ltc2485.o
>  obj-$(CONFIG_MAX1027) += max1027.o
>  obj-$(CONFIG_MAX11100) += max11100.o
>  obj-$(CONFIG_MAX1363) += max1363.o
> +obj-$(CONFIG_MAX9611) += max9611.o
>  obj-$(CONFIG_MCP320X) += mcp320x.o
>  obj-$(CONFIG_MCP3422) += mcp3422.o
>  obj-$(CONFIG_MEDIATEK_MT6577_AUXADC) += mt6577_auxadc.o
> diff --git a/drivers/iio/adc/max9611.c b/drivers/iio/adc/max9611.c
> new file mode 100644
> index 0000000..e5aaf73
> --- /dev/null
> +++ b/drivers/iio/adc/max9611.c
> @@ -0,0 +1,583 @@
> +/*
> + * iio/adc/max9611.c
> + *
> + * Maxim max9611/max9612 high side current sense amplifier with
> + * 12-bit ADC interface.
> + *
> + * Copyright (C) 2017 Jacopo Mondi
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + */
> +
> +/*
> + * This driver supports input common-mode voltage, current-sense
> + * amplifier with programmable gains and die temperature reading from
> + * Maxim max9611/max9612.
> + *
> + * Op-amp, analog comparator, and watchdog functionalities are not
> + * supported by this driver.
> + */
> +
> +#include <linux/delay.h>
> +#include <linux/i2c.h>
> +#include <linux/iio/iio.h>
> +#include <linux/iio/sysfs.h>
> +#include <linux/module.h>
> +#include <linux/of_device.h>
> +
> +#define DRIVER_NAME 			"max9611"
> +#define MAX9611_DEV_NAME		"max9611"
> +#define MAX9612_DEV_NAME		"max9612"
Really trivial, but what do these defines give us other than
making the code slightly harder to review?

Just put them inline where they are used.
> +
> +/* max9611 register addresses */
> +#define MAX9611_REG_CSA_DATA		0x00
> +#define MAX9611_REG_RS_DATA		0x02
> +#define MAX9611_REG_TEMP_DATA		0x08
> +#define MAX9611_REG_CTRL1		0x0a
> +#define MAX9611_REG_CTRL2		0x0b
> +
> +/* max9611 REG1 mux configuration options */
> +#define MAX9611_MUX_MASK		GENMASK(3,0)
> +#define MAX9611_MUX_SENSE_1x		0x00
> +#define MAX9611_MUX_SENSE_4x		0x01
> +#define MAX9611_MUX_SENSE_8x		0x02
> +#define MAX9611_INPUT_VOLT		0x03
> +#define MAX9611_MUX_TEMP		0x06
> +
> +/* max9611 voltage (both csa and input) helper macros */
> +#define MAX9611_VOLTAGE_SHIFT		0x04
> +#define MAX9611_VOLTAGE_RAW(_r)		((_r) >> MAX9611_VOLTAGE_SHIFT)
> +
> +/*
> + * max9611 current sense amplifier voltage output:
> + * LSB and offset values depends on selected gain (1x, 4x, 8x)
> + *
> + * GAIN		LSB (nV)	OFFSET (LSB steps)
> + * 1x		107500		1
> + * 4x		26880		1
> + * 8x		13440		3
> + *
> + * The complete formula to calculate current sense voltage is:
> + *     (((adc_read >> 4) - offset) / ((1 / LSB) * 10^-3)
> + */
> +#define MAX9611_CSA_1X_LSB_nV		107500
> +#define MAX9611_CSA_4X_LSB_nV		26880
> +#define MAX9611_CSA_8X_LSB_nV		13440
> +
> +#define MAX9611_CSA_1X_OFFS_RAW		1
> +#define MAX9611_CSA_4X_OFFS_RAW		1
> +#define MAX9611_CSA_8X_OFFS_RAW		3
> +
> +/*
> + * max9611 common input mode (CIM): LSB is 14mV, with 14mV offset at 25 C
> + *
> + * The complete formula to calculate input common voltage is:
> + *     (((adc_read >> 4) * 1000) - offset) / (1 / 14 * 1000)
> + */
> +#define MAX9611_CIM_LSB_mV		14
> +#define MAX9611_CIM_OFFSET_RAW		1
> +
> +/*
> + * max9611 temperature reading: LSB is 480 milli degrees Celsius
> + *
> + * The complete formula to calculate temperature is:
> + *     ((adc_read >> 7) * 1000) / (1 / 480 * 1000)
> + */
> +#define MAX9611_TEMP_MAX_POS		0x7f80
> +#define MAX9611_TEMP_MAX_NEG		0xff80
> +#define MAX9611_TEMP_MIN_NEG		0xd980
> +#define MAX9611_TEMP_MASK		GENMASK(7, 15)
> +#define MAX9611_TEMP_SHIFT		0x07
> +#define MAX9611_TEMP_RAW(_r)		((_r) >> MAX9611_TEMP_SHIFT)
> +#define MAX9611_TEMP_SCALE_NUM		1000000
> +#define MAX9611_TEMP_SCALE_DIV		2083
> +
> +struct max9611_dev {
> +	struct device *dev;
> +	struct i2c_client *i2c_client;
> +	struct mutex lock;
> +	unsigned int shunt_resistor_uohm;
> +};
> +
> +enum max9611_conf_ids {
> +	CONF_SENSE_1x,
> +	CONF_SENSE_4x,
> +	CONF_SENSE_8x,
> +	CONF_IN_VOLT,
> +	CONF_TEMP,
> +};
> +
> +/**
> + * max9611_mux_conf - associate ADC mux configuration with register address
> + *		      where data shall be read from
> + */
> +static const unsigned int max9611_mux_conf[][2] = {
> +	/* CONF_SENSE_1x */
> +	{ MAX9611_MUX_SENSE_1x, MAX9611_REG_CSA_DATA },
> +	/* CONF_SENSE_4x */
> +	{ MAX9611_MUX_SENSE_4x, MAX9611_REG_CSA_DATA },
> +	/* CONF_SENSE_8x */
> +	{ MAX9611_MUX_SENSE_8x, MAX9611_REG_CSA_DATA },
> +	/* CONF_IN_VOLT */
> +	{ MAX9611_INPUT_VOLT, MAX9611_REG_RS_DATA },
> +	/* CONF_TEMP */
> +	{ MAX9611_MUX_TEMP, MAX9611_REG_TEMP_DATA },
> +};
> +
> +enum max9611_csa_gain {
> +	CSA_GAIN_1x,
> +	CSA_GAIN_4x,
> +	CSA_GAIN_8x,
> +};
> +
> +enum max9611_csa_gain_params {
> +	CSA_GAIN_LSB_nV,
> +	CSA_GAIN_OFFS_RAW,
> +};
> +
> +/**
> + * max9611_csa_gain_conf - associate gain multiplier with LSB and
> + *			   offset values.
> + *
> + * Group together parameters associated with configurable gain
> + * on current sense amplifier path to ADC interface.
> + * Current sense read routine adjusts gain until it gets a meaningful
> + * value; use this structure to retrieve the correct LSB and offset values.
> + */
> +static const unsigned int max9611_gain_conf[][2] = {
> +	{ /* [0] CSA_GAIN_1x */
> +		MAX9611_CSA_1X_LSB_nV,
> +		MAX9611_CSA_1X_OFFS_RAW,
> +	},
> +	{ /* [1] CSA_GAIN_4x */
> +		MAX9611_CSA_4X_LSB_nV,
> +		MAX9611_CSA_4X_OFFS_RAW,
> +	},
> +	{ /* [2] CSA_GAIN_8x */
> +		MAX9611_CSA_8X_LSB_nV,
> +		MAX9611_CSA_8X_OFFS_RAW,
> +	},
> +};
> +
> +enum max9611_chan_addrs {
> +	MAX9611_CHAN_VOLTAGE_INPUT,
> +	MAX9611_CHAN_VOLTAGE_SENSE,
> +	MAX9611_CHAN_TEMPERATURE,
> +	MAX9611_CHAN_CURRENT_LOAD,
> +	MAX9611_CHAN_POWER_LOAD,
> +};
> +
> +static const struct iio_chan_spec max9611_channels[] = {
> +	{
> +	  .type			= IIO_TEMP,
> +	  .info_mask_separate	= BIT(IIO_CHAN_INFO_RAW) |
> +				  BIT(IIO_CHAN_INFO_SCALE),
> +	  .address		= MAX9611_CHAN_TEMPERATURE,
> +	},
> +	{
> +	  .type			= IIO_VOLTAGE,
> +	  .info_mask_separate	= BIT(IIO_CHAN_INFO_PROCESSED),
> +	  .address		= MAX9611_CHAN_VOLTAGE_SENSE,
> +	  .indexed		= 1,
> +	  .channel		= 0,
> +	},
> +	{
> +	  .type			= IIO_VOLTAGE,
> +	  .info_mask_separate	= BIT(IIO_CHAN_INFO_RAW)   |
> +				  BIT(IIO_CHAN_INFO_SCALE) |
> +				  BIT(IIO_CHAN_INFO_OFFSET),
> +	  .address		= MAX9611_CHAN_VOLTAGE_INPUT,
> +	  .indexed		= 1,
> +	  .channel		= 1,
> +	},
> +	{
> +	  .type			= IIO_CURRENT,
> +	  .info_mask_separate	= BIT(IIO_CHAN_INFO_PROCESSED),
> +	  .address		= MAX9611_CHAN_CURRENT_LOAD,
> +	},
> +	{
> +	  .type			= IIO_POWER,
> +	  .info_mask_separate	= BIT(IIO_CHAN_INFO_PROCESSED),
> +	  .address		= MAX9611_CHAN_POWER_LOAD
> +	},
> +};
> +
> +/**
> + * max9611_read_single() - read a single value from ADC interface
> + *
> + * Data registers are 16 bit long, spread between two 8 bit registers
> + * with consecutive addresses.
> + * Configure ADC mux first, then read register at address "reg_addr".
> + * The smbus_read_word routine asks for 16 bits and the ADC is kind enough
> + * to return values from "reg_addr" and "reg_addr + 1" consecutively.
> + * Data are transmitted with big-endian ordering: MSB arrives first.
> + *
> + * @max9611: max9611 device
> + * @selector: index for mux and register configuration
> + * @raw_val: the value returned from ADC
> + */
> +static int max9611_read_single(struct max9611_dev *max9611,
> +			       enum max9611_conf_ids selector,
> +			       u16 *raw_val)
> +{
> +	int ret;
> +
> +	u8 mux_conf = max9611_mux_conf[selector][0] & MAX9611_MUX_MASK;
> +	u8 reg_addr = max9611_mux_conf[selector][1];
> +
> +	/*
> +	 * Keep mutex lock held during read-write to avoid mux register
> +	 * (CTRL1) re-configuration.
> +	 */
> +	mutex_lock(&max9611->lock);
> +	ret = i2c_smbus_write_byte_data(max9611->i2c_client,
> +					MAX9611_REG_CTRL1, mux_conf);
> +	if (ret) {
> +		dev_err(max9611->dev, "i2c write byte failed: 0x%2x - 0x%2x\n",
> +			MAX9611_REG_CTRL1, mux_conf);
> +		mutex_unlock(&max9611->lock);
> +		return ret;
> +	}
> +
> +	/*
> +	 * need a delay here to make register configuration
> +	 * stabilize. 1 msec at least, from empirical testing.
> +	 */
> +	usleep_range(1000, 2000);
> +
> +	ret = i2c_smbus_read_word_swapped(max9611->i2c_client, reg_addr);
> +	if (ret < 0) {
> +		dev_err(max9611->dev, "i2c read word from 0x%2x failed\n",
> +			reg_addr);
> +		mutex_unlock(&max9611->lock);
> +		return ret;
> +	}
> +
> +	*raw_val = ret;
> +	mutex_unlock(&max9611->lock);
> +
> +	return 0;
> +}
> +
> +/**
> + * max9611_read_csa_voltage() - read current sense amplifier output voltage
> + *
> + * Current sense amplifier output voltage is read through a configurable
> + * 1x, 4x or 8x gain.
> + * Start with plain 1x gain, and adjust gain control properly until a
> + * meaningful value is read from ADC output.
> + *
> + * @max9611: max9611 device
> + * @adc_raw: raw value read from ADC output
> + * @csa_gain: gain configuration option selector
> + */
> +static int max9611_read_csa_voltage(struct max9611_dev *max9611,
> +				    u16 *adc_raw,
> +				    enum max9611_csa_gain *csa_gain)
> +{
> +	enum max9611_conf_ids gain_selectors[] = {
> +		CONF_SENSE_1x,
> +		CONF_SENSE_4x,
> +		CONF_SENSE_8x
> +	};
> +	unsigned int i;
> +	int ret;
> +
> +	for (i = 0; i < ARRAY_SIZE(gain_selectors); ++i) {
> +		ret = max9611_read_single(max9611, gain_selectors[i], adc_raw);
> +		if (ret)
> +			return ret;
> +
> +		if (*adc_raw > 0) {
> +			*csa_gain = gain_selectors[i];
> +			return 0;
> +		}
> +	}
> +
> +	return -EIO;
> +}
> +
> +static int max9611_read_raw(struct iio_dev *indio_dev,
> +			    struct iio_chan_spec const *chan,
> +			    int *val, int *val2, long mask)
> +{
> +	struct max9611_dev *dev = iio_priv(indio_dev);
> +	enum max9611_csa_gain gain_selector;
> +	const unsigned int *csa_gain;
> +	u16 adc_data;
> +	int ret;
> +
> +	switch (mask) {
> +	case IIO_CHAN_INFO_RAW:
> +
> +		switch (chan->address) {
> +		case MAX9611_CHAN_TEMPERATURE:
> +			ret = max9611_read_single(dev, CONF_TEMP,
> +						  &adc_data);
> +			if (ret)
> +				return -EINVAL;
> +
> +			*val = MAX9611_TEMP_RAW(adc_data);
> +			return IIO_VAL_INT;
> +
> +		case MAX9611_CHAN_VOLTAGE_INPUT:
> +			ret = max9611_read_single(dev, CONF_IN_VOLT,
> +						  &adc_data);
> +			if (ret)
> +				return -EINVAL;
> +
> +			*val = MAX9611_VOLTAGE_RAW(adc_data);
> +			return IIO_VAL_INT;
> +		}
> +
> +		break;
> +
> +	case IIO_CHAN_INFO_OFFSET:
> +		/* MAX9611_CHAN_VOLTAGE_INPUT */
> +		*val = MAX9611_CIM_OFFSET_RAW;
> +
> +		return IIO_VAL_INT;
> +
> +	case IIO_CHAN_INFO_SCALE:
> +
> +		switch (chan->address) {
> +		case MAX9611_CHAN_TEMPERATURE:
> +			*val = MAX9611_TEMP_SCALE_NUM;
> +			*val2 = MAX9611_TEMP_SCALE_DIV;
> +
> +			return IIO_VAL_FRACTIONAL;
> +
> +		case MAX9611_CHAN_VOLTAGE_INPUT:
> +			*val = MAX9611_CIM_LSB_mV;
> +
> +			return IIO_VAL_INT;
> +		}
> +
> +		break;
> +
> +	case IIO_CHAN_INFO_PROCESSED:
> +
> +		switch (chan->address) {
> +		case MAX9611_CHAN_VOLTAGE_SENSE:
> +			/*
> +			 * processed (mV): (raw - offset) * LSB (nV) / 10^6
> +			 *
> +			 * Even if max9611 can output raw csa voltage readings,
> +			 * use a produced value as scale depends on gain.
> +			 */
> +			ret = max9611_read_csa_voltage(dev, &adc_data,
> +						       &gain_selector);
> +			if (ret)
> +				return -EINVAL;
> +
> +			csa_gain = max9611_gain_conf[gain_selector];
> +
> +			adc_data -= csa_gain[CSA_GAIN_OFFS_RAW];
> +			*val = MAX9611_VOLTAGE_RAW(adc_data) *
> +			       csa_gain[CSA_GAIN_LSB_nV];
> +			*val2 = 1000000;
> +
> +			return IIO_VAL_FRACTIONAL;
> +
> +		case MAX9611_CHAN_CURRENT_LOAD:
> +			/* processed (mA): Vcsa (nV) / Rshunt (uOhm)  */
> +			ret = max9611_read_csa_voltage(dev, &adc_data,
> +						       &gain_selector);
> +			if (ret)
> +				return -EINVAL;
> +
> +			csa_gain = max9611_gain_conf[gain_selector];
> +
> +			adc_data -= csa_gain[CSA_GAIN_OFFS_RAW];
> +			*val = MAX9611_VOLTAGE_RAW(adc_data) *
> +			       csa_gain[CSA_GAIN_LSB_nV];
> +			*val2 = dev->shunt_resistor_uohm;
> +
> +			return IIO_VAL_FRACTIONAL;
> +
> +		case MAX9611_CHAN_POWER_LOAD:
> +			/*
> +			 * processed (mW): Vin (mV) * Vcsa (uV) /
> +			 *		   Rshunt (uOhm)
> +			 */
> +			ret = max9611_read_single(dev, CONF_IN_VOLT,
> +						  &adc_data);
> +			if (ret)
> +				return -EINVAL;
> +
> +			adc_data -= MAX9611_CIM_OFFSET_RAW;
> +			*val = MAX9611_VOLTAGE_RAW(adc_data) *
> +			       MAX9611_CIM_LSB_mV;
> +
> +			ret = max9611_read_csa_voltage(dev, &adc_data,
> +						       &gain_selector);
> +			if (ret)
> +				return -EINVAL;
> +
> +			csa_gain = max9611_gain_conf[gain_selector];
> +
> +			/* divide by 10^3 here to avoid 32bit overflow */
> +			adc_data -= csa_gain[CSA_GAIN_OFFS_RAW];
> +			*val *= MAX9611_VOLTAGE_RAW(adc_data) *
> +				csa_gain[CSA_GAIN_LSB_nV] / 1000;
> +			*val2 = dev->shunt_resistor_uohm;
> +
> +			return IIO_VAL_FRACTIONAL;
> +		}
> +
> +		break;
> +	}
> +
> +	return -EINVAL;
> +}
> +
> +static ssize_t max9611_shunt_resistor_show(struct device *dev,
> +					   struct device_attribute *attr,
> +					   char *buf)
> +{
> +	struct max9611_dev *max9611 = iio_priv(dev_to_iio_dev(dev));
> +
> +	return sprintf(buf, "%u\n", max9611->shunt_resistor_uohm);
Oops didn't pick up on this before.  Should really be ohms with
appropriate fixed point arithmetic.

This would match with the use of ohms for DPOT devices that we already
have documented.
> +}
> +
> +static IIO_DEVICE_ATTR(in_power_shunt_resistor, 0444,
> +		       max9611_shunt_resistor_show, NULL, 0);
> +static IIO_DEVICE_ATTR(in_current_shunt_resistor, 0444,
> +		       max9611_shunt_resistor_show, NULL, 0);
> +
> +static struct attribute *max9611_attributes[] = {
> +	&iio_dev_attr_in_power_shunt_resistor.dev_attr.attr,
> +	&iio_dev_attr_in_current_shunt_resistor.dev_attr.attr,
> +	NULL,
> +};
> +
> +static const struct attribute_group max9611_attribute_group = {
> +	.attrs = max9611_attributes,
> +};
> +
> +static const struct iio_info indio_info = {
> +	.driver_module	= THIS_MODULE,
> +	.read_raw	= max9611_read_raw,
> +	.attrs		= &max9611_attribute_group,
> +};
> +
> +static int max9611_init(struct max9611_dev *max9611)
> +{
> +	struct i2c_client *client = max9611->i2c_client;
> +	u16 regval;
> +	int ret;
> +
> +	if (!i2c_check_functionality(client->adapter,
> +				     I2C_FUNC_SMBUS_WRITE_BYTE	|
> +				     I2C_FUNC_SMBUS_READ_WORD_DATA)) {
> +		dev_err(max9611->dev,
> +			"I2c adapter does not support smbus write_byte or read_word functionalities: aborting probe.\n");
> +		return -EINVAL;
> +	}
> +
> +	/* Make sure die temperature is in range to test communications. */
> +	ret = max9611_read_single(max9611, CONF_TEMP, &regval);
> +	if (ret)
> +		return ret;
> +
> +	regval = ret & MAX9611_TEMP_MASK;
> +
> +	if ((regval > MAX9611_TEMP_MAX_POS &&
> +	     regval < MAX9611_TEMP_MIN_NEG) ||
> +	     regval > MAX9611_TEMP_MAX_NEG) {
> +		dev_err(max9611->dev,
> +			"Invalid value received from ADC 0x%4x: aborting\n",
> +			regval);
> +		return -EIO;
> +	}
> +
> +	/* Mux shall be zeroed back before applying other configurations */
> +	ret = i2c_smbus_write_byte_data(max9611->i2c_client,
> +					MAX9611_REG_CTRL1, 0);
> +	if (ret) {
> +		dev_err(max9611->dev, "i2c write byte failed: 0x%2x - 0x%2x\n",
> +			MAX9611_REG_CTRL1, 0);
> +		return ret;
> +	}
> +
> +	ret = i2c_smbus_write_byte_data(max9611->i2c_client,
> +					MAX9611_REG_CTRL2, 0);
> +	if (ret) {
> +		dev_err(max9611->dev, "i2c write byte failed: 0x%2x - 0x%2x\n",
> +			MAX9611_REG_CTRL2, 0);
> +		return ret;
> +	}
> +	usleep_range(1000, 2000);
> +
> +	return 0;
> +}
> +
> +static const struct of_device_id max9611_of_table[] = {
> +	{.compatible = "maxim,max9611", .data = MAX9611_DEV_NAME},
> +	{.compatible = "maxim,max9612", .data = MAX9612_DEV_NAME},
> +	{ },
> +};
> +
> +MODULE_DEVICE_TABLE(of, max9611_of_table);
> +static int max9611_probe(struct i2c_client *client,
> +			 const struct i2c_device_id *id)
> +{
> +	const char * const shunt_res_prop = "shunt-resistor-uohm";
> +	const struct device_node *of_node = client->dev.of_node;
> +	const struct of_device_id *of_id =
> +		of_match_device(max9611_of_table, &client->dev);
> +	struct max9611_dev *max9611;
> +	struct iio_dev *indio_dev;
> +	unsigned int of_shunt;
> +	int ret;
> +
> +	indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*max9611));
> +	if (IS_ERR(indio_dev))
> +		return PTR_ERR(indio_dev);
> +
> +	i2c_set_clientdata(client, indio_dev);
> +
> +	max9611			= iio_priv(indio_dev);
> +	max9611->dev		= &client->dev;
> +	max9611->i2c_client	= client;
> +	mutex_init(&max9611->lock);
> +
> +	ret = of_property_read_u32(of_node, shunt_res_prop, &of_shunt);
> +	if (ret) {
> +		dev_err(&client->dev,
> +			"Missing %s property for %s node\n",
> +			shunt_res_prop, of_node->full_name);
> +		return ret;
> +	}
> +	max9611->shunt_resistor_uohm = of_shunt;
> +
> +	ret = max9611_init(max9611);
> +	if (ret)
> +		return ret;
> +
> +	indio_dev->dev.parent	= &client->dev;
> +	indio_dev->dev.of_node	= client->dev.of_node;
> +	indio_dev->name		= of_id->data;
> +	indio_dev->modes	= INDIO_DIRECT_MODE;
> +	indio_dev->info		= &indio_info;
> +	indio_dev->channels	= max9611_channels;
> +	indio_dev->num_channels	= ARRAY_SIZE(max9611_channels);
> +
> +	return devm_iio_device_register(&client->dev, indio_dev);
> +}
> +
> +static struct i2c_driver max9611_driver = {
> +	.driver = {
> +		   .name = DRIVER_NAME,
> +		   .owner = THIS_MODULE,
> +		   .of_match_table = max9611_of_table,
> +	},
> +	.probe = max9611_probe,
> +};
> +module_i2c_driver(max9611_driver);
> +
> +MODULE_AUTHOR("Jacopo Mondi <jacopo+renesas@jmondi.org>");
> +MODULE_DESCRIPTION("Maxim max9611/12 current sense amplifier with 12bit ADC");
> +MODULE_LICENSE("GPL v2");
> 

Re: [PATCH v4 2/4] iio: Documentation: Add max9611 sysfs documentation

[Jonathan Cameron]

On 02/04/17 10:36, Jonathan Cameron wrote:
> On 27/03/17 16:12, Jacopo Mondi wrote:
>> Add documentation for max9611 driver.
>> Document attributes describing value of shunt resistor installed between
>> RS+ and RS- voltage sense inputs.
>>
>> Signed-off-by: Jacopo Mondi <jacopo+renesas@jmondi.org>
> Good.  Will pick up once the binding is sorted.
> 
> Kick me if I don't!
Oops. Missed the units being micro ohms.  They want to be ohms to be consistent
within the ABI.

We let various odd units go in right back at the beginning to try and remain
compatible with hwmon.  Turned out to be a bad idea.  Also the ina2xx uses
ohms and you should stay consistent with that.

Thanks,

Jonathan
>> ---
>>  Documentation/ABI/testing/sysfs-bus-iio-adc-max9611 | 17 +++++++++++++++++
>>  1 file changed, 17 insertions(+)
>>  create mode 100644 Documentation/ABI/testing/sysfs-bus-iio-adc-max9611
>>
>> diff --git a/Documentation/ABI/testing/sysfs-bus-iio-adc-max9611 b/Documentation/ABI/testing/sysfs-bus-iio-adc-max9611
>> new file mode 100644
>> index 0000000..5020d00
>> --- /dev/null
>> +++ b/Documentation/ABI/testing/sysfs-bus-iio-adc-max9611
>> @@ -0,0 +1,17 @@
>> +What:		/sys/bus/iio/devices/iio:deviceX/in_power_shunt_resistor
>> +Date:		March 2017
>> +KernelVersion:	4.12
>> +Contact:	linux-iio@vger.kernel.org
>> +Description: 	The value of the shunt resistor used to compute power drain on
>> +                common input voltage pin (RS+). In micro Ohms.
>> +
>> +What:		/sys/bus/iio/devices/iio:deviceX/in_current_shunt_resistor
>> +Date:		March 2017
>> +KernelVersion:	4.12
>> +Contact:	linux-iio@vger.kernel.org
>> +Description: 	The value of the shunt resistor used to compute current flowing
>> +                between RS+ and RS- voltage sense inputs. In micro Ohms.
>> +
>> +These attributes describe a single physical component, exposed as two distinct
>> +attributes as it is used to calculate two different values: power load and
>> +current flowing between RS+ and RS- inputs.
>>
> 
> --
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> 

Re: [PATCH v4 1/4] Documentation: dt-bindings: iio: Add max9611 ADC

[Rob Herring]

On Mon, Mar 27, 2017 at 05:12:55PM +0200, Jacopo Mondi wrote:
> Add device tree bindings documentation for Maxim max9611/max9612 current
> sense amplifier.

"dt-bindings: iio: adc: ..." for the subject.

> 
> Signed-off-by: Jacopo Mondi <jacopo+renesas@jmondi.org>
> ---
>  .../devicetree/bindings/iio/adc/max9611.txt        | 26 ++++++++++++++++++++++
>  1 file changed, 26 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/iio/adc/max9611.txt
> 
> diff --git a/Documentation/devicetree/bindings/iio/adc/max9611.txt b/Documentation/devicetree/bindings/iio/adc/max9611.txt
> new file mode 100644
> index 0000000..8430d3b
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/iio/adc/max9611.txt
> @@ -0,0 +1,26 @@
> +* Maxim max9611/max9612 current sense amplifier with 12-bits ADC interface
> +
> +Maxim max9611/max9612 is an high-side current sense amplifier with integrated
> +12-bits ADC communicating over I2c bus.
> +The device node for this driver shall be a child of a I2c controller.
> +
> +Required properties
> +  - compatible: Should be "maxim,max9611" or "maxim,max9612"
> +  - reg: The 7-bits long I2c address of the device
> +  - shunt-resistor-uohm: Value, in uOhm, of the current sense shunt resistor

As Jonathan said.

> +
> +Example:
> +
> +&i2c4 {
> +	csa: adc@7c {
> +		compatible = "maxim,max9611";
> +		reg = <0x7c>;
> +
> +		shunt-resistor-uohm = <5000>;
> +	};
> +};
> +
> +This device node describes a current sense amplifier sitting on I2c4 bus
> +with address 0x7c (read address is 0xf9, write address is 0xf8).
> +A sense resistor of 0,005 Ohm is installed between RS+ and RS- current-sensing
> +inputs.
> -- 
> 2.7.4
>