[PATCH 0/3] pmbus: Expand fan support and add MAX31785 driver

[PATCH 0/3] pmbus: Expand fan support and add MAX31785 driver

[Andrew Jeffery]

Hello,

Previously I'd posted a second RFC series implementing fan control support in
PMBus core and adding a driver for the MAX31785 fan controller:

  https://www.spinics.net/lists/kernel/msg2558128.html

I think the core changes have settled enough to move the effort out of RFC-land.

This series is some modest refinements on the core based on previous feedback,
and polishes the driver implementation by defining and implementing devicetree
bindings for the controller.

The series has been tested on a number of IBM Witherspoon systems, which
contain the fan controller of interest.

Please review!

Andrew

Changes between RFC v2 to (non-RFC) v1

* Clean up issues identified in comments on the pmbus core changes 
* Define and implement bindings for the MAX31785
* Clean up issues identified in comments on the max31785 driver

Andrew Jeffery (3):
  dt-bindings: hwmon: pmbus: Add Maxim MAX31785 documentation
  hwmon: pmbus: Add fan control support
  pmbus: Add driver for Maxim MAX31785 Intelligent Fan Controller

 .../devicetree/bindings/hwmon/pmbus/max31785.txt   | 117 ++++
 drivers/hwmon/pmbus/Kconfig                        |  10 +
 drivers/hwmon/pmbus/Makefile                       |   1 +
 drivers/hwmon/pmbus/max31785.c                     | 670 +++++++++++++++++++++
 drivers/hwmon/pmbus/pmbus.h                        |  29 +
 drivers/hwmon/pmbus/pmbus_core.c                   | 222 ++++++-
 6 files changed, 1034 insertions(+), 15 deletions(-)
 create mode 100644 Documentation/devicetree/bindings/hwmon/pmbus/max31785.txt
 create mode 100644 drivers/hwmon/pmbus/max31785.c

-- 
2.11.0

[PATCH 1/3] dt-bindings: hwmon: pmbus: Add Maxim MAX31785 documentation

[Andrew Jeffery]

Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
---
 .../devicetree/bindings/hwmon/pmbus/max31785.txt   | 117 +++++++++++++++++++++
 1 file changed, 117 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/hwmon/pmbus/max31785.txt

diff --git a/Documentation/devicetree/bindings/hwmon/pmbus/max31785.txt b/Documentation/devicetree/bindings/hwmon/pmbus/max31785.txt
new file mode 100644
index 000000000000..96e705434a59
--- /dev/null
+++ b/Documentation/devicetree/bindings/hwmon/pmbus/max31785.txt
@@ -0,0 +1,117 @@
+Bindings for the Maxim MAX31785 Intelligent Fan Controller
+==========================================================
+
+Reference:
+[1] https://datasheets.maximintegrated.com/en/ds/MAX31785.pdf
+
+Required properties:
+- compatible     : One of "maxim,max31785" or "maxim,max31785a"
+- reg            : I2C address, one of 0x52, 0x53, 0x54, 0x55.
+- #address-cells : Must be 1
+- #size-cells    : Must be 0
+
+Capabilities are configured through subnodes of the controller's node.
+
+Fans
+----
+
+Only fans with subnodes present will be marked as installed.
+
+Required subnode properties:
+- compatible             : Must be "pmbus-fan"
+- reg                    : The PMBus page the properties apply to.
+- maxim,fan-rotor-input  : The type of rotor measurement provided to the
+                           controller. Must be either "tach" for tachometer
+                           pulses or "lock" for a locked-rotor signal.
+- maxim,fan-lock-polarity: Required iff maxim,fan-rotor-input is "lock". Valid
+                           values are "low" for active low, "high" for active
+                           high.
+
+Optional subnode properties:
+- fan-mode               : "rpm" or "pwm". Default value is "pwm".
+- tach-pulses            : Tachometer pulses per revolution. Valid values are
+                           1, 2, 3 or 4. The default is 1.
+- maxim,fan-no-fault-ramp: Do not ramp the fan to 100% PWM duty on detecting a
+                           fan fault
+- maxim,fan-startup      : The number of rotations required before taking
+                           emergency action for an unresponsive fan and driving
+                           it with 100% or 0% PWM duty, depending on the state
+                           of maxim,fan-no-fault-ramp. Valid values are 0
+                           (automatic spin-up disabled), 2, 4, or 8. Default
+                           value is 0.
+- maxim,fan-health       : Enable automated fan health check
+- maxim,fan-ramp         : Configures how fast the device ramps the PWM duty
+                           cycle from one value to another. Valid values are 0
+                           to 7 inclusive, with values 0 - 2 configuring a
+                           1000ms update rate and 1 - 3% duty respective duty
+                           increase, and 3 - 7 a 200ms update rate with a 1 -
+                           5% respective duty increase. Default value is 0.
+- maxim,fan-no-watchdog  : Do not ramp fan to 100% PWM duty on failure to
+                           update desired fan rate inside 10s. This implies
+                           maxim,tmp-no-fault-ramp
+- maxim,tmp-no-fault-ramp: Do not ramp fan to 100% PWM duty on temperature
+                           sensor fault detection. This implies
+                           maxim,fan-no-watchdog
+- maxim,tmp-hysteresis   : The temperature hysteresis used to determine
+                           transitions to lower fan speed bands in the
+                           temperature/fan rate lookup table. Valid values are
+                           2, 4, 6 or 8 (degrees celcius). Default value is 2.
+- maxim,fan-dual-tach    : Enable dual tachometer functionality
+- maxim,fan-pwm-freq     : The PWM frequency. Valid values are 30, 50, 100, 150
+                           and 25000 (Hz). Default value is 30Hz.
+- maxim,fan-lookup-table : A 16-element cell array of alternating temperature
+                           and rate values representing the look up table. The
+                           rate units are set through the fan-mode property.
+- maxim,fan-fault-pin-mon: Ramp fans to 100% PWM duty when the FAULT pin is
+                           asserted
+
+Temperature
+-----------
+
+Required subnode properties:
+- compatible    : Must be "pmbus-temperature"
+- reg           : The PMBus page the properties apply to.
+
+Optional subnode properties:
+- maxim,tmp-offset      : Valid values are 0 - 30 (degrees celcius) inclusive.
+                          Default value is 0.
+- maxim,tmp-fans        : An array of fan indexes whose fans are controlled by
+                          the current temperature sensor. Fans are indexed from
+                          zero. The valid values are 0 - 5 inclusive.
+
+Example:
+	fan-max31785: max31785@52 {
+		reg = <0x52>;
+		compatible = "maxim,max31785";
+                #address-cells = <1>;
+                #size-cells = <0>;
+
+                fan@0 {
+                        compatible = "pmbus-fan";
+                        reg = <0>;
+                        mode = "rpm";
+                        tach-pulses = <1>;
+                        maxim,fan-rotor-input = "tach";
+                        maxim,fan-dual-tach;
+                };
+
+                fan@1 {
+                        compatible = "pmbus-fan";
+                        reg = <1>;
+                        mode = "rpm";
+                        tach-pulses = <1>;
+                        maxim,fan-rotor-input = "tach";
+                        maxim,tmp-hysteresis = <2>;
+                        maxim,fan-lookup-table = <
+                        /*  Temperature    RPM  */
+                                 0        1000
+                                10        2000
+                                20        3000
+                                30        4000
+                                40        5000
+                                50        6000
+                                60        7000
+                                70        8000
+                        >;
+                };
+	};
-- 
2.11.0

[PATCH 2/3] hwmon: pmbus: Add fan control support

[Andrew Jeffery]

Expose fanX_target, pwmX and pwmX_enable hwmon sysfs attributes.

Fans in a PMBus device are driven by the configuration of two registers:
FAN_CONFIG_x_y and FAN_COMMAND_x: FAN_CONFIG_x_y dictates how the fan
and the tacho operate (if installed), while FAN_COMMAND_x sets the
desired fan rate. The unit of FAN_COMMAND_x is dependent on the
operational fan mode, RPM or PWM percent duty, as determined by the
corresponding FAN_CONFIG_x_y.

The mapping of fanX_target, pwmX and pwmX_enable onto FAN_CONFIG_x_y and
FAN_COMMAND_x is implemented with the addition of virtual registers and
generic implementations in the core:

1. PMBUS_VIRT_FAN_TARGET_x
2. PMBUS_VIRT_PWM_x
3. PMBUS_VIRT_PWM_ENABLE_x

The facilitate the necessary side-effects of each access. Examples of
the read case, assuming m = 1, b = 0, R = 0:

             Read     |              With              || Gives
         -------------------------------------------------------
           Attribute  | FAN_CONFIG_x_y | FAN_COMMAND_y || Value
         ----------------------------------------------++-------
          fanX_target | ~PB_FAN_z_RPM  | 0x0001        || 1
          pwm1        | ~PB_FAN_z_RPM  | 0x0064        || 255
          pwmX_enable | ~PB_FAN_z_RPM  | 0x0001        || 1
          fanX_target |  PB_FAN_z_RPM  | 0x0001        || 1
          pwm1        |  PB_FAN_z_RPM  | 0x0064        || 0
          pwmX_enable |  PB_FAN_z_RPM  | 0x0001        || 1

And the write case:

             Write    | With  ||               Sets
         -------------+-------++----------------+---------------
           Attribute  | Value || FAN_CONFIG_x_y | FAN_COMMAND_x
         -------------+-------++----------------+---------------
          fanX_target | 1     ||  PB_FAN_z_RPM  | 0x0001
          pwmX        | 255   || ~PB_FAN_z_RPM  | 0x0064
          pwmX_enable | 1     || ~PB_FAN_z_RPM  | 0x0064

Also, the DIRECT mode scaling of some controllers is different between
RPM and PWM percent duty control modes, so PSC_PWM is introduced to
capture the necessary coefficients.

Signed-off-by: Andrew Jeffery <andrew-zrmu5oMJ5Fs@public.gmane.org>
---
 drivers/hwmon/pmbus/pmbus.h      |  29 +++++
 drivers/hwmon/pmbus/pmbus_core.c | 222 ++++++++++++++++++++++++++++++++++++---
 2 files changed, 236 insertions(+), 15 deletions(-)

diff --git a/drivers/hwmon/pmbus/pmbus.h b/drivers/hwmon/pmbus/pmbus.h
index bfcb13bae34b..a863b8fed16f 100644
--- a/drivers/hwmon/pmbus/pmbus.h
+++ b/drivers/hwmon/pmbus/pmbus.h
@@ -190,6 +190,28 @@ enum pmbus_regs {
 	PMBUS_VIRT_VMON_UV_FAULT_LIMIT,
 	PMBUS_VIRT_VMON_OV_FAULT_LIMIT,
 	PMBUS_VIRT_STATUS_VMON,
+
+	/*
+	 * RPM and PWM Fan control
+	 *
+	 * Drivers wanting to expose PWM control must define the behaviour of
+	 * PMBUS_VIRT_PWM_ENABLE_[1-4] in the {read,write}_word_data callback.
+	 *
+	 * pmbus core provides default implementations for
+	 * PMBUS_VIRT_FAN_TARGET_[1-4] and PMBUS_VIRT_PWM_[1-4].
+	 */
+	PMBUS_VIRT_FAN_TARGET_1,
+	PMBUS_VIRT_FAN_TARGET_2,
+	PMBUS_VIRT_FAN_TARGET_3,
+	PMBUS_VIRT_FAN_TARGET_4,
+	PMBUS_VIRT_PWM_1,
+	PMBUS_VIRT_PWM_2,
+	PMBUS_VIRT_PWM_3,
+	PMBUS_VIRT_PWM_4,
+	PMBUS_VIRT_PWM_ENABLE_1,
+	PMBUS_VIRT_PWM_ENABLE_2,
+	PMBUS_VIRT_PWM_ENABLE_3,
+	PMBUS_VIRT_PWM_ENABLE_4,
 };
 
 /*
@@ -223,6 +245,8 @@ enum pmbus_regs {
 #define PB_FAN_1_RPM			BIT(6)
 #define PB_FAN_1_INSTALLED		BIT(7)
 
+enum pmbus_fan_mode { percent = 0, rpm };
+
 /*
  * STATUS_BYTE, STATUS_WORD (lower)
  */
@@ -313,6 +337,7 @@ enum pmbus_sensor_classes {
 	PSC_POWER,
 	PSC_TEMPERATURE,
 	PSC_FAN,
+	PSC_PWM,
 	PSC_NUM_CLASSES		/* Number of power sensor classes */
 };
 
@@ -339,6 +364,8 @@ enum pmbus_sensor_classes {
 #define PMBUS_HAVE_STATUS_FAN34	BIT(17)
 #define PMBUS_HAVE_VMON		BIT(18)
 #define PMBUS_HAVE_STATUS_VMON	BIT(19)
+#define PMBUS_HAVE_PWM12	BIT(20)
+#define PMBUS_HAVE_PWM34	BIT(21)
 
 enum pmbus_data_format { linear = 0, direct, vid };
 enum vrm_version { vr11 = 0, vr12 };
@@ -413,6 +440,8 @@ int pmbus_write_byte_data(struct i2c_client *client, int page, u8 reg,
 			  u8 value);
 int pmbus_update_byte_data(struct i2c_client *client, int page, u8 reg,
 			   u8 mask, u8 value);
+int pmbus_update_fan(struct i2c_client *client, int page, int id,
+		     u8 config, u8 mask, u16 command);
 void pmbus_clear_faults(struct i2c_client *client);
 bool pmbus_check_byte_register(struct i2c_client *client, int page, int reg);
 bool pmbus_check_word_register(struct i2c_client *client, int page, int reg);
diff --git a/drivers/hwmon/pmbus/pmbus_core.c b/drivers/hwmon/pmbus/pmbus_core.c
index ba59eaef2e07..3c8bcbdf1d88 100644
--- a/drivers/hwmon/pmbus/pmbus_core.c
+++ b/drivers/hwmon/pmbus/pmbus_core.c
@@ -63,6 +63,7 @@ struct pmbus_sensor {
 	u16 reg;		/* register */
 	enum pmbus_sensor_classes class;	/* sensor class */
 	bool update;		/* runtime sensor update needed */
+	bool convert;		/* Whether or not to apply linear/vid/direct */
 	int data;		/* Sensor data.
 				   Negative if there was a read error */
 };
@@ -118,6 +119,27 @@ struct pmbus_data {
 	u8 currpage;
 };
 
+static const int pmbus_fan_rpm_mask[] = {
+	PB_FAN_1_RPM,
+	PB_FAN_2_RPM,
+	PB_FAN_1_RPM,
+	PB_FAN_2_RPM,
+};
+
+static const int pmbus_fan_config_registers[] = {
+	PMBUS_FAN_CONFIG_12,
+	PMBUS_FAN_CONFIG_12,
+	PMBUS_FAN_CONFIG_34,
+	PMBUS_FAN_CONFIG_34
+};
+
+static const int pmbus_fan_command_registers[] = {
+	PMBUS_FAN_COMMAND_1,
+	PMBUS_FAN_COMMAND_2,
+	PMBUS_FAN_COMMAND_3,
+	PMBUS_FAN_COMMAND_4,
+};
+
 void pmbus_clear_cache(struct i2c_client *client)
 {
 	struct pmbus_data *data = i2c_get_clientdata(client);
@@ -188,6 +210,29 @@ int pmbus_write_word_data(struct i2c_client *client, u8 page, u8 reg, u16 word)
 }
 EXPORT_SYMBOL_GPL(pmbus_write_word_data);
 
+int pmbus_update_fan(struct i2c_client *client, int page, int id,
+			       u8 config, u8 mask, u16 command)
+{
+	int from, rv;
+	u8 to;
+
+	from = pmbus_read_byte_data(client, page,
+				    pmbus_fan_config_registers[id]);
+	if (from < 0)
+		return from;
+
+	to = (from & ~mask) | (config & mask);
+
+	rv = pmbus_write_byte_data(client, page,
+				   pmbus_fan_config_registers[id], to);
+	if (rv < 0)
+		return rv;
+
+	return pmbus_write_word_data(client, page,
+				     pmbus_fan_command_registers[id], command);
+}
+EXPORT_SYMBOL_GPL(pmbus_update_fan);
+
 /*
  * _pmbus_write_word_data() is similar to pmbus_write_word_data(), but checks if
  * a device specific mapping function exists and calls it if necessary.
@@ -204,8 +249,40 @@ static int _pmbus_write_word_data(struct i2c_client *client, int page, int reg,
 		if (status != -ENODATA)
 			return status;
 	}
-	if (reg >= PMBUS_VIRT_BASE)
-		return -ENXIO;
+	if (reg >= PMBUS_VIRT_BASE) {
+		int id, bit;
+
+		switch (reg) {
+		case PMBUS_VIRT_FAN_TARGET_1:
+		case PMBUS_VIRT_FAN_TARGET_2:
+		case PMBUS_VIRT_FAN_TARGET_3:
+		case PMBUS_VIRT_FAN_TARGET_4:
+			id = reg - PMBUS_VIRT_FAN_TARGET_1;
+			bit = pmbus_fan_rpm_mask[id];
+			status = pmbus_update_fan(client, page, id, bit, bit,
+						  word);
+			break;
+		case PMBUS_VIRT_PWM_1:
+		case PMBUS_VIRT_PWM_2:
+		case PMBUS_VIRT_PWM_3:
+		case PMBUS_VIRT_PWM_4:
+		{
+			u32 command = word;
+
+			id = reg - PMBUS_VIRT_PWM_1;
+			bit = pmbus_fan_rpm_mask[id];
+			command *= 100;
+			command /= 255;
+			status = pmbus_update_fan(client, page, id, 0, bit,
+						  command);
+			break;
+		}
+		default:
+			status = -ENXIO;
+			break;
+		}
+		return status;
+	}
 	return pmbus_write_word_data(client, page, reg, word);
 }
 
@@ -221,6 +298,9 @@ int pmbus_read_word_data(struct i2c_client *client, u8 page, u8 reg)
 }
 EXPORT_SYMBOL_GPL(pmbus_read_word_data);
 
+static int pmbus_get_fan_command(struct i2c_client *client, int page, int id,
+				 enum pmbus_fan_mode mode);
+
 /*
  * _pmbus_read_word_data() is similar to pmbus_read_word_data(), but checks if
  * a device specific mapping function exists and calls it if necessary.
@@ -236,8 +316,42 @@ static int _pmbus_read_word_data(struct i2c_client *client, int page, int reg)
 		if (status != -ENODATA)
 			return status;
 	}
-	if (reg >= PMBUS_VIRT_BASE)
-		return -ENXIO;
+	if (reg >= PMBUS_VIRT_BASE) {
+		int id;
+
+		switch (reg) {
+		case PMBUS_VIRT_FAN_TARGET_1:
+		case PMBUS_VIRT_FAN_TARGET_2:
+		case PMBUS_VIRT_FAN_TARGET_3:
+		case PMBUS_VIRT_FAN_TARGET_4:
+			id = reg - PMBUS_VIRT_FAN_TARGET_1;
+			status = pmbus_get_fan_command(client, page, id, rpm);
+			break;
+		case PMBUS_VIRT_PWM_1:
+		case PMBUS_VIRT_PWM_2:
+		case PMBUS_VIRT_PWM_3:
+		case PMBUS_VIRT_PWM_4:
+		{
+			int rv;
+
+			id = reg - PMBUS_VIRT_PWM_1;
+			rv = pmbus_get_fan_command(client, page, id, percent);
+			if (rv < 0)
+				return rv;
+
+			rv *= 255;
+			rv /= 100;
+
+			status = rv;
+			break;
+		}
+		default:
+			status = -ENXIO;
+			break;
+		}
+
+		return status;
+	}
 	return pmbus_read_word_data(client, page, reg);
 }
 
@@ -304,6 +418,28 @@ static int _pmbus_read_byte_data(struct i2c_client *client, int page, int reg)
 	return pmbus_read_byte_data(client, page, reg);
 }
 
+static int pmbus_get_fan_command(struct i2c_client *client, int page, int id,
+				 enum pmbus_fan_mode mode)
+{
+	int config;
+
+	config = _pmbus_read_byte_data(client, page,
+				       pmbus_fan_config_registers[id]);
+	if (config < 0)
+		return config;
+
+	/*
+	 * We can't meaningfully translate between PWM and RPM, so if the
+	 * attribute mode (fan[1-*]_target is RPM, pwm[1-*] and pwm[1-*]_enable
+	 * are PWM) doesn't match the hardware mode, then report 0 instead.
+	 */
+	if ((mode == rpm) != (!!(config & pmbus_fan_rpm_mask[id])))
+		return 0;
+
+	return _pmbus_read_word_data(client, page,
+				     pmbus_fan_command_registers[id]);
+}
+
 static void pmbus_clear_fault_page(struct i2c_client *client, int page)
 {
 	_pmbus_write_byte(client, page, PMBUS_CLEAR_FAULTS);
@@ -489,7 +625,7 @@ static long pmbus_reg2data_direct(struct pmbus_data *data,
 	/* X = 1/m * (Y * 10^-R - b) */
 	R = -R;
 	/* scale result to milli-units for everything but fans */
-	if (sensor->class != PSC_FAN) {
+	if (!(sensor->class == PSC_FAN || sensor->class == PSC_PWM)) {
 		R += 3;
 		b *= 1000;
 	}
@@ -539,6 +675,9 @@ static long pmbus_reg2data(struct pmbus_data *data, struct pmbus_sensor *sensor)
 {
 	long val;
 
+	if (!sensor->convert)
+		return sensor->data;
+
 	switch (data->info->format[sensor->class]) {
 	case direct:
 		val = pmbus_reg2data_direct(data, sensor);
@@ -642,7 +781,7 @@ static u16 pmbus_data2reg_direct(struct pmbus_data *data,
 	}
 
 	/* Calculate Y = (m * X + b) * 10^R */
-	if (sensor->class != PSC_FAN) {
+	if (!(sensor->class == PSC_FAN || sensor->class == PSC_PWM)) {
 		R -= 3;		/* Adjust R and b for data in milli-units */
 		b *= 1000;
 	}
@@ -673,6 +812,9 @@ static u16 pmbus_data2reg(struct pmbus_data *data,
 {
 	u16 regval;
 
+	if (!sensor->convert)
+		return val;
+
 	switch (data->info->format[sensor->class]) {
 	case direct:
 		regval = pmbus_data2reg_direct(data, sensor, val);
@@ -895,12 +1037,18 @@ static struct pmbus_sensor *pmbus_add_sensor(struct pmbus_data *data,
 		return NULL;
 	a = &sensor->attribute;
 
-	snprintf(sensor->name, sizeof(sensor->name), "%s%d_%s",
-		 name, seq, type);
+	if (type)
+		snprintf(sensor->name, sizeof(sensor->name), "%s%d_%s",
+			 name, seq, type);
+	else
+		snprintf(sensor->name, sizeof(sensor->name), "%s%d",
+			 name, seq);
+
 	sensor->page = page;
 	sensor->reg = reg;
 	sensor->class = class;
 	sensor->update = update;
+	sensor->convert = true;
 	pmbus_dev_attr_init(a, sensor->name,
 			    readonly ? S_IRUGO : S_IRUGO | S_IWUSR,
 			    pmbus_show_sensor, pmbus_set_sensor);
@@ -1558,13 +1706,6 @@ static const int pmbus_fan_registers[] = {
 	PMBUS_READ_FAN_SPEED_4
 };
 
-static const int pmbus_fan_config_registers[] = {
-	PMBUS_FAN_CONFIG_12,
-	PMBUS_FAN_CONFIG_12,
-	PMBUS_FAN_CONFIG_34,
-	PMBUS_FAN_CONFIG_34
-};
-
 static const int pmbus_fan_status_registers[] = {
 	PMBUS_STATUS_FAN_12,
 	PMBUS_STATUS_FAN_12,
@@ -1587,6 +1728,48 @@ static const u32 pmbus_fan_status_flags[] = {
 };
 
 /* Fans */
+static int pmbus_add_fan_ctrl(struct i2c_client *client,
+		struct pmbus_data *data, int index, int page, int id,
+		u8 config)
+{
+	struct pmbus_sensor *sensor;
+	int rv;
+
+	rv = _pmbus_read_word_data(client, page,
+				   pmbus_fan_command_registers[id]);
+	if (rv < 0)
+		return rv;
+
+	sensor = pmbus_add_sensor(data, "fan", "target", index, page,
+				  PMBUS_VIRT_FAN_TARGET_1 + id, PSC_FAN,
+				  true, false);
+
+	if (!sensor)
+		return -ENOMEM;
+
+	if (!((data->info->func[page] & PMBUS_HAVE_PWM12) ||
+			(data->info->func[page] & PMBUS_HAVE_PWM34)))
+		return 0;
+
+	sensor = pmbus_add_sensor(data, "pwm", NULL, index, page,
+				  PMBUS_VIRT_PWM_1 + id, PSC_PWM,
+				  true, false);
+
+	if (!sensor)
+		return -ENOMEM;
+
+	sensor = pmbus_add_sensor(data, "pwm", "enable", index, page,
+				  PMBUS_VIRT_PWM_ENABLE_1 + id, PSC_PWM,
+				  true, false);
+
+	if (!sensor)
+		return -ENOMEM;
+
+	sensor->convert = false;
+
+	return 0;
+}
+
 static int pmbus_add_fan_attributes(struct i2c_client *client,
 				    struct pmbus_data *data)
 {
@@ -1624,6 +1807,15 @@ static int pmbus_add_fan_attributes(struct i2c_client *client,
 					     PSC_FAN, true, true) == NULL)
 				return -ENOMEM;
 
+			/* Fan control */
+			if (pmbus_check_word_register(client, page,
+					pmbus_fan_command_registers[f])) {
+				ret = pmbus_add_fan_ctrl(client, data, index,
+							 page, f, regval);
+				if (ret < 0)
+					return ret;
+			}
+
 			/*
 			 * Each fan status register covers multiple fans,
 			 * so we have to do some magic.
-- 
2.11.0

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[PATCH 3/3] pmbus: Add driver for Maxim MAX31785 Intelligent Fan Controller

[Andrew Jeffery]

The Maxim MAX31785 is a PMBus device providing closed-loop,
multi-channel fan management with temperature and remote voltage
sensing. Various fan control features are provided, including PWM
frequency control, temperature hysteresis, dual tachometer measurements,
and fan health monitoring.

The driver implementation makes use of the new fan control virtual
registers exposed by the pmbus core. It mixes use of the default
implementations with some overrides via the read/write handlers to
handle FAN_COMMAND_1 on the MAX31785, whose definition breaks the value
range into various control bands dependent on RPM or PWM mode.

The dual tachometer feature is implemented in hardware with a TACHSEL
line to indicate the rotor under measurement, and exposed on the bus by
extending the READ_FAN_SPEED_1 word with two extra bytes*.
The need to read the non-standard four-byte response leads to a cut-down
implementation of i2c_smbus_xfer_emulated() included in the driver.
Further, to expose the second rotor tachometer value to userspace,
virtual fans are implemented by re-routing the FAN_CONFIG_1_2 register
from the undefined (in hardware) pages 23-28 to the same register on
pages 0-5, and similarly re-routing READ_FAN_SPEED_1 requests on 23-28
to pages 0-5 but extracting the second word of the four-byte response.

* The documentation recommends the slower rotor be associated with
TACHSEL=0, which provides the first word of the response. The TACHSEL=0
measurement is used by the controller's closed-loop fan management.

Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
---
 drivers/hwmon/pmbus/Kconfig    |  10 +
 drivers/hwmon/pmbus/Makefile   |   1 +
 drivers/hwmon/pmbus/max31785.c | 670 +++++++++++++++++++++++++++++++++++++++++
 3 files changed, 681 insertions(+)
 create mode 100644 drivers/hwmon/pmbus/max31785.c

diff --git a/drivers/hwmon/pmbus/Kconfig b/drivers/hwmon/pmbus/Kconfig
index cad1229b7e17..5f2f3c6c7499 100644
--- a/drivers/hwmon/pmbus/Kconfig
+++ b/drivers/hwmon/pmbus/Kconfig
@@ -95,6 +95,16 @@ config SENSORS_MAX20751
 	  This driver can also be built as a module. If so, the module will
 	  be called max20751.
 
+config SENSORS_MAX31785
+	tristate "Maxim MAX31785 and compatibles"
+	default n
+	help
+	  If you say yes here you get hardware monitoring support for Maxim
+	  MAX31785.
+
+	  This driver can also be built as a module. If so, the module will
+	  be called max31785.
+
 config SENSORS_MAX34440
 	tristate "Maxim MAX34440 and compatibles"
 	default n
diff --git a/drivers/hwmon/pmbus/Makefile b/drivers/hwmon/pmbus/Makefile
index 562132054aaf..4ea548a8af46 100644
--- a/drivers/hwmon/pmbus/Makefile
+++ b/drivers/hwmon/pmbus/Makefile
@@ -10,6 +10,7 @@ obj-$(CONFIG_SENSORS_LTC2978)	+= ltc2978.o
 obj-$(CONFIG_SENSORS_LTC3815)	+= ltc3815.o
 obj-$(CONFIG_SENSORS_MAX16064)	+= max16064.o
 obj-$(CONFIG_SENSORS_MAX20751)	+= max20751.o
+obj-$(CONFIG_SENSORS_MAX31785)	+= max31785.o
 obj-$(CONFIG_SENSORS_MAX34440)	+= max34440.o
 obj-$(CONFIG_SENSORS_MAX8688)	+= max8688.o
 obj-$(CONFIG_SENSORS_TPS40422)	+= tps40422.o
diff --git a/drivers/hwmon/pmbus/max31785.c b/drivers/hwmon/pmbus/max31785.c
new file mode 100644
index 000000000000..1c2648ce5322
--- /dev/null
+++ b/drivers/hwmon/pmbus/max31785.c
@@ -0,0 +1,670 @@
+/*
+ * Copyright (C) 2017 IBM Corp.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/err.h>
+#include <linux/i2c.h>
+#include "pmbus.h"
+
+enum max31785_regs {
+	MFR_REVISION		= 0x9b,
+	MFR_FAULT_RESPONSE	= 0xd9,
+	MFR_TEMP_SENSOR_CONFIG	= 0xf0,
+	MFR_FAN_CONFIG		= 0xf1,
+	MFR_READ_FAN_PWM	= 0xf3,
+	MFR_FAN_FAULT_LIMIT	= 0xf5,
+	MFR_FAN_WARN_LIMIT	= 0xf6,
+	MFR_FAN_PWM_AVG		= 0xf8,
+};
+
+#define MAX31785			0x3030
+#define MAX31785A			0x3040
+
+#define MFR_TEMP_SENSOR_CONFIG_ENABLE	BIT(15)
+#define MFR_TEMP_SENSOR_CONFIG_OFFSET	GENMASK(14, 10)
+
+#define MFR_FAN_CONFIG_FREQ		GENMASK(15, 13)
+#define MFR_FAN_CONFIG_DUAL_TACH	BIT(12)
+#define MFR_FAN_CONFIG_HYS		GENMASK(11, 10)
+#define MFR_FAN_CONFIG_TSFO		BIT(9)
+#define MFR_FAN_CONFIG_TACHO		BIT(8)
+#define MFR_FAN_CONFIG_RAMP		GENMASK(7, 5)
+#define MFR_FAN_CONFIG_HEALTH		BIT(4)
+#define MFR_FAN_CONFIG_ROTOR_HI_LO	BIT(3)
+#define MFR_FAN_CONFIG_ROTOR		BIT(2)
+#define MFR_FAN_CONFIG_SPIN		GENMASK(1, 0)
+
+#define MFR_FAULT_RESPONSE_MONITOR	BIT(0)
+
+#define MAX31785_CAP_READ_DUAL_TACH	BIT(0)
+
+#define MAX31785_NR_PAGES		23
+
+static int max31785_read_byte_data(struct i2c_client *client, int page,
+				   int reg)
+{
+	switch (reg) {
+	case PMBUS_VOUT_MODE:
+		if (page < MAX31785_NR_PAGES)
+			return -ENODATA;
+
+		return -ENOTSUPP;
+	case PMBUS_FAN_CONFIG_12:
+		if (page < MAX31785_NR_PAGES)
+			return -ENODATA;
+
+		return pmbus_read_byte_data(client, page - MAX31785_NR_PAGES,
+					    reg);
+	}
+
+	return -ENODATA;
+}
+
+static int max31785_write_byte(struct i2c_client *client, int page, u8 value)
+{
+	if (page < MAX31785_NR_PAGES)
+		return -ENODATA;
+
+	return -ENOTSUPP;
+}
+
+static int max31785_read_long_data(struct i2c_client *client, int page,
+				   int reg, u32 *data)
+{
+	unsigned char cmdbuf[1];
+	unsigned char rspbuf[4];
+	int rc;
+
+	struct i2c_msg msg[2] = {
+		{
+			.addr = client->addr,
+			.flags = 0,
+			.len = sizeof(cmdbuf),
+			.buf = cmdbuf,
+		},
+		{
+			.addr = client->addr,
+			.flags = I2C_M_RD,
+			.len = sizeof(rspbuf),
+			.buf = rspbuf,
+		},
+	};
+
+	cmdbuf[0] = reg;
+
+	rc = pmbus_set_page(client, page);
+	if (rc < 0)
+		return rc;
+
+	rc = i2c_transfer(client->adapter, msg, ARRAY_SIZE(msg));
+	if (rc < 0)
+		return rc;
+
+	*data = (rspbuf[0] << (0 * 8)) | (rspbuf[1] << (1 * 8)) |
+		(rspbuf[2] << (2 * 8)) | (rspbuf[3] << (3 * 8));
+
+	return rc;
+}
+
+static int max31785_get_pwm(struct i2c_client *client, int page)
+{
+	int config;
+	int command;
+
+	config = pmbus_read_byte_data(client, page, PMBUS_FAN_CONFIG_12);
+	if (config < 0)
+		return config;
+
+	command = pmbus_read_word_data(client, page, PMBUS_FAN_COMMAND_1);
+	if (command < 0)
+		return command;
+
+	if (!(config & PB_FAN_1_RPM)) {
+		if (command >= 0x8000)
+			return 0;
+		else if (command >= 0x2711)
+			return 0x2710;
+
+		return command;
+	}
+
+	return 0;
+}
+
+static int max31785_get_pwm_mode(struct i2c_client *client, int page)
+{
+	int config;
+	int command;
+
+	config = pmbus_read_byte_data(client, page, PMBUS_FAN_CONFIG_12);
+	if (config < 0)
+		return config;
+
+	command = pmbus_read_word_data(client, page, PMBUS_FAN_COMMAND_1);
+	if (command < 0)
+		return command;
+
+	if (!(config & PB_FAN_1_RPM)) {
+		if (command >= 0x8000)
+			return 2;
+		else if (command >= 0x2711)
+			return 0;
+
+		return 1;
+	}
+
+	return (command >= 0x8000) ? 2 : 1;
+}
+
+static int max31785_read_word_data(struct i2c_client *client, int page,
+				   int reg)
+{
+	int rv;
+
+	switch (reg) {
+	case PMBUS_READ_FAN_SPEED_1:
+	{
+		u32 val;
+
+		if (page < MAX31785_NR_PAGES)
+			return -ENODATA;
+
+		rv = max31785_read_long_data(client, page - MAX31785_NR_PAGES,
+					     reg, &val);
+		if (rv < 0)
+			return rv;
+
+		rv = (val >> 16) & 0xffff;
+		break;
+	}
+	case PMBUS_VIRT_PWM_1:
+		if (page >= MAX31785_NR_PAGES)
+			return -ENOTSUPP;
+
+		rv = max31785_get_pwm(client, page);
+		if (rv < 0)
+			return rv;
+
+		rv *= 255;
+		rv /= 100;
+		break;
+	case PMBUS_VIRT_PWM_ENABLE_1:
+		if (page >= MAX31785_NR_PAGES)
+			return -ENOTSUPP;
+
+		rv = max31785_get_pwm_mode(client, page);
+		break;
+	default:
+		rv = (page >= MAX31785_NR_PAGES) ? -ENXIO : -ENODATA;
+		break;
+	}
+
+	return rv;
+}
+
+static const int max31785_pwm_modes[] = { 0x7fff, 0x2710, 0xffff };
+
+static int max31785_write_word_data(struct i2c_client *client, int page,
+				    int reg, u16 word)
+{
+	if (page >= MAX31785_NR_PAGES)
+		return -ENXIO;
+
+	switch (reg) {
+	case PMBUS_VIRT_PWM_ENABLE_1:
+		if (word >= ARRAY_SIZE(max31785_pwm_modes))
+			return -EINVAL;
+
+		return pmbus_update_fan(client, page, 0, 0, PB_FAN_1_RPM,
+					max31785_pwm_modes[word]);
+	default:
+		break;
+	}
+
+	return -ENODATA;
+}
+
+/*
+ * Returns negative error codes if an unrecoverable problem is detected, 0 if a
+ * recoverable problem is detected, or a positive value on success.
+ */
+static int max31785_of_fan_config(struct i2c_client *client,
+				  struct pmbus_driver_info *info,
+				  u32 capabilities, struct device_node *child)
+{
+	int mfr_cfg = 0, mfr_fault_resp = 0, pb_cfg;
+	struct device *dev = &client->dev;
+	char *lock_polarity = NULL;
+	const char *sval;
+	u32 page;
+	u32 uval;
+	int ret;
+
+	if (!of_device_is_compatible(child, "pmbus-fan"))
+		return 0;
+
+	ret = of_property_read_u32(child, "reg", &page);
+	if (ret < 0) {
+		dev_err(&client->dev, "Missing valid reg property\n");
+		return ret;
+	}
+
+	if (!(info->func[page] & PMBUS_HAVE_FAN12)) {
+		dev_err(dev, "Page %d does not have fan capabilities\n", page);
+		return -ENXIO;
+	}
+
+	ret = i2c_smbus_write_byte_data(client, PMBUS_PAGE, page);
+	if (ret < 0)
+		return ret;
+
+	pb_cfg = i2c_smbus_read_byte_data(client, PMBUS_FAN_CONFIG_12);
+	if (pb_cfg < 0)
+		return pb_cfg;
+
+	if (!(pb_cfg & PB_FAN_1_INSTALLED)) {
+		dev_warn(dev, "Fan %d is configured but not installed\n", page);
+		return 0;
+	}
+
+	ret = of_property_read_string(child, "maxim,fan-rotor-input", &sval);
+	if (ret < 0) {
+		dev_err(dev, "Missing valid maxim,fan-rotor-input property for fan %d\n",
+				page);
+		return ret;
+	}
+
+	if (strcmp("tach", sval) && strcmp("lock", sval)) {
+		dev_err(dev, "maxim,fan-rotor-input has invalid value for fan %d: %s\n",
+				page, sval);
+		return -EINVAL;
+	} else if (!strcmp("lock", sval)) {
+		mfr_cfg |= MFR_FAN_CONFIG_ROTOR;
+
+		ret = i2c_smbus_write_word_data(client, MFR_FAN_FAULT_LIMIT, 1);
+		if (ret < 0)
+			return ret;
+
+		ret = of_property_read_string(child, "maxim,fan-lock-polarity",
+					      &sval);
+		if (ret < 0) {
+			dev_err(dev, "Missing valid maxim,fan-lock-polarity property for fan %d\n",
+					page);
+			return ret;
+		}
+
+		if (strcmp("low", sval) && strcmp("high", sval)) {
+			dev_err(dev, "maxim,fan-lock-polarity has invalid value for fan %d: %s\n",
+					page, lock_polarity);
+			return -EINVAL;
+		} else if (!strcmp("high", sval))
+			mfr_cfg |= MFR_FAN_CONFIG_ROTOR_HI_LO;
+	}
+
+	if (!of_property_read_string(child, "fan-mode", &sval)) {
+		if (!strcmp("rpm", sval))
+			pb_cfg |= PB_FAN_1_RPM;
+		else if (!strcmp("pwm", sval))
+			pb_cfg &= ~PB_FAN_1_RPM;
+		else {
+			dev_err(dev, "fan-mode has invalid value for fan %d: %s\n",
+					page, sval);
+			return -EINVAL;
+		}
+	}
+
+	ret = of_property_read_u32(child, "tach-pulses", &uval);
+	if (ret < 0) {
+		pb_cfg &= ~PB_FAN_1_PULSE_MASK;
+	} else if (uval && (uval - 1) < 4) {
+		pb_cfg = ((pb_cfg & ~PB_FAN_1_PULSE_MASK) | ((uval - 1) << 4));
+	} else {
+		dev_err(dev, "tach-pulses has invalid value for fan %d: %u\n",
+				page, uval);
+		return -EINVAL;
+	}
+
+	if (of_property_read_bool(child, "maxim,fan-health"))
+		mfr_cfg |= MFR_FAN_CONFIG_HEALTH;
+
+	if (of_property_read_bool(child, "maxim,fan-no-watchdog") ||
+		of_property_read_bool(child, "maxim,tmp-no-fault-ramp"))
+		mfr_cfg |= MFR_FAN_CONFIG_TSFO;
+
+	if (of_property_read_bool(child, "maxim,fan-dual-tach")) {
+		mfr_cfg |= MFR_FAN_CONFIG_DUAL_TACH;
+
+		if (capabilities & MAX31785_CAP_READ_DUAL_TACH) {
+			int virtual = MAX31785_NR_PAGES + page;
+
+			info->pages = max(info->pages, virtual + 1);
+			info->func[virtual] |= PMBUS_HAVE_FAN12;
+		}
+	}
+
+	if (of_property_read_bool(child, "maxim,fan-no-fault-ramp"))
+		mfr_cfg |= MFR_FAN_CONFIG_TACHO;
+
+	if (!of_property_read_u32(child, "maxim,fan-startup", &uval)) {
+		uval /= 2;
+		if (uval < 5) {
+			mfr_cfg |= uval;
+		} else {
+			dev_err(dev, "maxim,fan-startup has invalid value for fan %d: %u\n",
+					page, uval);
+			return -EINVAL;
+		}
+	}
+
+	if (!of_property_read_u32(child, "maxim,fan-ramp", &uval)) {
+		if (uval < 8) {
+			mfr_cfg |= uval << 5;
+		} else {
+			dev_err(dev, "maxim,fan-ramp has invalid value for fan %d: %u\n",
+					page, uval);
+			return -EINVAL;
+		}
+	}
+
+	if (!of_property_read_u32(child, "maxim,tmp-hysteresis", &uval)) {
+		uval /= 2;
+		uval -= 1;
+		if (uval < 4) {
+			mfr_cfg |= uval << 10;
+		} else {
+			dev_err(dev, "maxim,tmp-hysteresis has invalid value for fan %d, %u\n",
+					page, uval);
+			return -EINVAL;
+		}
+	}
+
+	if (!of_property_read_u32(child, "maxim,fan-pwm-freq", &uval)) {
+		u16 val;
+
+		if (uval == 30) {
+			val = 0;
+		} else if (uval == 50) {
+			val = 1;
+		} else if (uval == 100) {
+			val = 2;
+		} else if (uval == 150) {
+			val = 3;
+		} else if (uval == 25000) {
+			val = 7;
+		} else {
+			dev_err(dev, "maxim,fan-pwm-freq has invalid value for fan %d: %u\n",
+					page, uval);
+			return -EINVAL;
+		}
+
+		mfr_cfg |= val << 13;
+	}
+
+	if (of_property_read_bool(child, "maxim,fan-fault-pin-mon"))
+		mfr_fault_resp |= MFR_FAULT_RESPONSE_MONITOR;
+
+	ret = i2c_smbus_write_byte_data(client, PMBUS_FAN_CONFIG_12,
+					pb_cfg & ~PB_FAN_1_INSTALLED);
+	if (ret < 0)
+		return ret;
+
+	ret = i2c_smbus_write_word_data(client, MFR_FAN_CONFIG, mfr_cfg);
+	if (ret < 0)
+		return ret;
+
+	ret = i2c_smbus_write_byte_data(client, MFR_FAULT_RESPONSE,
+					mfr_fault_resp);
+	if (ret < 0)
+		return ret;
+
+	ret = i2c_smbus_write_byte_data(client, PMBUS_FAN_CONFIG_12, pb_cfg);
+	if (ret < 0)
+		return ret;
+
+	/*
+	 * Fans are on pages 0 - 5. If the page property of a fan node is
+	 * greater than 5 we will have errored in checks above out above.
+	 * Therefore we don't need to cope with values up to 31, and the int
+	 * return type is enough.
+	 *
+	 * The bit mask return value is used to populate a bitfield of fans
+	 * who are both configured in the devicetree _and_ reported as
+	 * installed by the hardware. Any fans that are not configured in the
+	 * devicetree but are reported as installed by the hardware will have
+	 * their hardware configuration updated to unset the installed bit.
+	 */
+	return BIT(page);
+}
+
+static int max31785_of_tmp_config(struct i2c_client *client,
+				  struct pmbus_driver_info *info,
+				  struct device_node *child)
+{
+	struct device *dev = &client->dev;
+	u16 mfr_tmp_cfg = 0;
+	int nr_fans;
+	u32 page;
+	u32 uval;
+	int ret;
+	int i;
+
+	if (!of_device_is_compatible(child, "pmbus-temperature"))
+		return 0;
+
+	ret = of_property_read_u32(child, "reg", &page);
+	if (ret < 0) {
+		dev_err(&client->dev, "Missing valid reg property\n");
+		return ret;
+	}
+
+	if (!(info->func[page] & PMBUS_HAVE_TEMP)) {
+		dev_err(dev, "Page %d does not have temp capabilities\n", page);
+		return -ENXIO;
+	}
+
+	ret = i2c_smbus_write_byte_data(client, PMBUS_PAGE, page);
+	if (ret < 0)
+		return ret;
+
+	if (!of_property_read_u32(child, "maxim,tmp-offset", &uval)) {
+		if (uval < 32)
+			mfr_tmp_cfg |= uval << 10;
+	}
+
+	nr_fans = of_property_count_elems_of_size(child, "maxim,tmp-fans",
+						  sizeof(u32));
+	if (nr_fans > 0) {
+		mfr_tmp_cfg |= MFR_TEMP_SENSOR_CONFIG_ENABLE;
+
+		for (i = 0; i < nr_fans; i++) {
+			if (of_property_read_u32_index(child, "maxim,tmp-fans",
+						       i, &uval))
+				continue;
+
+			if (uval < 6)
+				mfr_tmp_cfg |= BIT(uval);
+		}
+	}
+
+	ret = i2c_smbus_write_word_data(client, MFR_TEMP_SENSOR_CONFIG,
+					mfr_tmp_cfg);
+	if (ret < 0)
+		return ret;
+
+	return 0;
+}
+
+#define MAX31785_FAN_FUNCS \
+	(PMBUS_HAVE_FAN12 | PMBUS_HAVE_STATUS_FAN12 | PMBUS_HAVE_PWM12)
+
+#define MAX31785_TEMP_FUNCS \
+	(PMBUS_HAVE_TEMP | PMBUS_HAVE_STATUS_TEMP)
+
+#define MAX31785_VOUT_FUNCS \
+	(PMBUS_HAVE_VOUT | PMBUS_HAVE_STATUS_VOUT)
+
+static const struct pmbus_driver_info max31785_info = {
+	.pages = MAX31785_NR_PAGES,
+
+	.write_word_data = max31785_write_word_data,
+	.read_byte_data = max31785_read_byte_data,
+	.read_word_data = max31785_read_word_data,
+	.write_byte = max31785_write_byte,
+
+	/* RPM */
+	.format[PSC_FAN] = direct,
+	.m[PSC_FAN] = 1,
+	.b[PSC_FAN] = 0,
+	.R[PSC_FAN] = 0,
+	/* PWM */
+	.format[PSC_PWM] = direct,
+	.m[PSC_PWM] = 1,
+	.b[PSC_PWM] = 0,
+	.R[PSC_PWM] = 2,
+	.func[0] = MAX31785_FAN_FUNCS,
+	.func[1] = MAX31785_FAN_FUNCS,
+	.func[2] = MAX31785_FAN_FUNCS,
+	.func[3] = MAX31785_FAN_FUNCS,
+	.func[4] = MAX31785_FAN_FUNCS,
+	.func[5] = MAX31785_FAN_FUNCS,
+
+	.format[PSC_TEMPERATURE] = direct,
+	.m[PSC_TEMPERATURE] = 1,
+	.b[PSC_TEMPERATURE] = 0,
+	.R[PSC_TEMPERATURE] = 2,
+	.func[6]  = MAX31785_TEMP_FUNCS,
+	.func[7]  = MAX31785_TEMP_FUNCS,
+	.func[8]  = MAX31785_TEMP_FUNCS,
+	.func[9]  = MAX31785_TEMP_FUNCS,
+	.func[10] = MAX31785_TEMP_FUNCS,
+	.func[11] = MAX31785_TEMP_FUNCS,
+	.func[12] = MAX31785_TEMP_FUNCS,
+	.func[13] = MAX31785_TEMP_FUNCS,
+	.func[14] = MAX31785_TEMP_FUNCS,
+	.func[15] = MAX31785_TEMP_FUNCS,
+	.func[16] = MAX31785_TEMP_FUNCS,
+
+	.format[PSC_VOLTAGE_OUT] = direct,
+	.m[PSC_VOLTAGE_OUT] = 1,
+	.b[PSC_VOLTAGE_OUT] = 0,
+	.R[PSC_VOLTAGE_OUT] = 0,
+	.func[17] = MAX31785_VOUT_FUNCS,
+	.func[18] = MAX31785_VOUT_FUNCS,
+	.func[19] = MAX31785_VOUT_FUNCS,
+	.func[20] = MAX31785_VOUT_FUNCS,
+	.func[21] = MAX31785_VOUT_FUNCS,
+	.func[22] = MAX31785_VOUT_FUNCS,
+};
+
+static int max31785_probe(struct i2c_client *client,
+			  const struct i2c_device_id *id)
+{
+	struct device *dev = &client->dev;
+	struct device_node *child;
+	struct pmbus_driver_info *info;
+	u32 fans;
+	u32 caps;
+	s64 ret;
+	int i;
+
+	info = devm_kzalloc(dev, sizeof(struct pmbus_driver_info), GFP_KERNEL);
+	if (!info)
+		return -ENOMEM;
+
+	*info = max31785_info;
+
+	ret = i2c_smbus_write_byte_data(client, PMBUS_PAGE, 255);
+	if (ret < 0)
+		return ret;
+
+	ret = i2c_smbus_read_word_data(client, MFR_REVISION);
+	if (ret < 0)
+		return ret;
+
+	caps = 0;
+	if (!strcmp("max31785a", id->name)) {
+		if (ret == MAX31785A)
+			caps |= MAX31785_CAP_READ_DUAL_TACH;
+		else
+			dev_warn(dev, "Expected max3175a, found max31785: cannot provide secondary tachometer readings\n");
+	} else if (!strcmp("max31785", id->name)) {
+		if (ret == MAX31785A)
+			dev_info(dev, "Expected max31785, found max3175a: suppressing secondary tachometer attributes\n");
+	} else {
+		return -EINVAL;
+	}
+
+
+	fans = 0;
+	for_each_child_of_node(dev->of_node, child) {
+		ret = max31785_of_fan_config(client, info, caps, child);
+		if (ret < 0) {
+			of_node_put(child);
+			return ret;
+		}
+
+		if (ret)
+			fans |= ret;
+
+		ret = max31785_of_tmp_config(client, info, child);
+		if (ret < 0) {
+			of_node_put(child);
+			return ret;
+		}
+	}
+
+	for (i = 0; i < MAX31785_NR_PAGES; i++) {
+		bool have_fan = !!(info->func[i] & PMBUS_HAVE_FAN12);
+		bool fan_configured = !!(fans & BIT(i));
+
+		if (!have_fan || fan_configured)
+			continue;
+
+		ret = i2c_smbus_write_byte_data(client, PMBUS_PAGE, i);
+		if (ret < 0)
+			return ret;
+
+		ret = i2c_smbus_read_byte_data(client, PMBUS_FAN_CONFIG_12);
+		if (ret < 0)
+			return ret;
+
+		ret &= ~PB_FAN_1_INSTALLED;
+		ret = i2c_smbus_write_word_data(client, PMBUS_FAN_CONFIG_12,
+						ret);
+		if (ret < 0)
+			return ret;
+	}
+
+	return pmbus_do_probe(client, id, info);
+}
+
+static const struct i2c_device_id max31785_id[] = {
+	{ "max31785", 0 },
+	{ "max31785a", 0 },
+	{ },
+};
+
+MODULE_DEVICE_TABLE(i2c, max31785_id);
+
+static struct i2c_driver max31785_driver = {
+	.driver = {
+		.name = "max31785",
+	},
+	.probe = max31785_probe,
+	.remove = pmbus_do_remove,
+	.id_table = max31785_id,
+};
+
+module_i2c_driver(max31785_driver);
+
+MODULE_AUTHOR("Andrew Jeffery <andrew@aj.id.au>");
+MODULE_DESCRIPTION("PMBus driver for the Maxim MAX31785");
+MODULE_LICENSE("GPL");
-- 
2.11.0