[PATCH 1/7] hwmon: (max31790) Rework to use regmap

[PATCH 1/7] hwmon: (max31790) Rework to use regmap

[Václav Kubernát]

Converting the driver to use regmap makes it more generic. It also makes
it a lot easier to debug through debugfs.

Signed-off-by: Václav Kubernát <kubernat@cesnet.cz>
---
 drivers/hwmon/Kconfig    |   1 +
 drivers/hwmon/max31790.c | 148 +++++++++++++++++++++++++++------------
 2 files changed, 105 insertions(+), 44 deletions(-)

diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
index 54f04e61fb83..c2ec57672c4e 100644
--- a/drivers/hwmon/Kconfig
+++ b/drivers/hwmon/Kconfig
@@ -1092,6 +1092,7 @@ config SENSORS_MAX6697
 config SENSORS_MAX31790
 	tristate "Maxim MAX31790 sensor chip"
 	depends on I2C
+	select REGMAP_I2C
 	help
 	  If you say yes here you get support for 6-Channel PWM-Output
 	  Fan RPM Controller.
diff --git a/drivers/hwmon/max31790.c b/drivers/hwmon/max31790.c
index 86e6c71db685..ca413985b5f9 100644
--- a/drivers/hwmon/max31790.c
+++ b/drivers/hwmon/max31790.c
@@ -12,6 +12,7 @@
 #include <linux/init.h>
 #include <linux/jiffies.h>
 #include <linux/module.h>
+#include <linux/regmap.h>
 #include <linux/slab.h>
 
 /* MAX31790 registers */
@@ -46,11 +47,35 @@
 
 #define NR_CHANNEL			6
 
+#define MAX31790_REG_USER_BYTE_67	0x67
+
+#define BULK_TO_U16(msb, lsb)		(((msb) << 8) + (lsb))
+#define U16_MSB(num)			(((num) & 0xFF00) >> 8)
+#define U16_LSB(num)			((num) & 0x00FF)
+
+static const struct regmap_range max31790_ro_range = {
+	.range_min = MAX31790_REG_TACH_COUNT(0),
+	.range_max = MAX31790_REG_PWMOUT(0) - 1,
+};
+
+static const struct regmap_access_table max31790_wr_table = {
+	.no_ranges = &max31790_ro_range,
+	.n_no_ranges = 1,
+};
+
+static const struct regmap_config max31790_regmap_config = {
+	.reg_bits = 8,
+	.val_bits = 8,
+	.reg_stride = 1,
+	.max_register = MAX31790_REG_USER_BYTE_67,
+	.wr_table = &max31790_wr_table,
+};
+
 /*
  * Client data (each client gets its own)
  */
 struct max31790_data {
-	struct i2c_client *client;
+	struct regmap *regmap;
 	struct mutex update_lock;
 	bool valid; /* zero until following fields are valid */
 	unsigned long last_updated; /* in jiffies */
@@ -67,53 +92,72 @@ struct max31790_data {
 static struct max31790_data *max31790_update_device(struct device *dev)
 {
 	struct max31790_data *data = dev_get_drvdata(dev);
-	struct i2c_client *client = data->client;
+	struct regmap *regmap = data->regmap;
 	struct max31790_data *ret = data;
 	int i;
 	int rv;
+	int val;
+	u8 val_bulk[2];
 
 	mutex_lock(&data->update_lock);
 
 	if (time_after(jiffies, data->last_updated + HZ) || !data->valid) {
-		rv = i2c_smbus_read_byte_data(client,
-				MAX31790_REG_FAN_FAULT_STATUS1);
+		rv = regmap_read(regmap,
+				 MAX31790_REG_FAN_FAULT_STATUS1,
+				 &val);
 		if (rv < 0)
 			goto abort;
-		data->fault_status = rv & 0x3F;
+		data->fault_status = val & 0x3F;
 
-		rv = i2c_smbus_read_byte_data(client,
-				MAX31790_REG_FAN_FAULT_STATUS2);
+		rv = regmap_read(regmap,
+				 MAX31790_REG_FAN_FAULT_STATUS2,
+				 &val);
 		if (rv < 0)
 			goto abort;
-		data->fault_status |= (rv & 0x3F) << 6;
+		data->fault_status |= (val & 0x3F) << 6;
 
 		for (i = 0; i < NR_CHANNEL; i++) {
-			rv = i2c_smbus_read_word_swapped(client,
-					MAX31790_REG_TACH_COUNT(i));
+			rv = regmap_bulk_read(regmap,
+					      MAX31790_REG_TACH_COUNT(i),
+					      val_bulk,
+					      2);
 			if (rv < 0)
 				goto abort;
-			data->tach[i] = rv;
+			data->tach[i] = BULK_TO_U16(val_bulk[0],
+						    val_bulk[1]);
 
 			if (data->fan_config[i]
 			    & MAX31790_FAN_CFG_TACH_INPUT) {
-				rv = i2c_smbus_read_word_swapped(client,
-					MAX31790_REG_TACH_COUNT(NR_CHANNEL
-								+ i));
+				rv = regmap_bulk_read(regmap,
+						      MAX31790_REG_TACH_COUNT(NR_CHANNEL
+									      + i),
+					      val_bulk,
+					      2);
 				if (rv < 0)
 					goto abort;
-				data->tach[NR_CHANNEL + i] = rv;
+
+				data->tach[NR_CHANNEL + i] =
+					BULK_TO_U16(val_bulk[0],
+						    val_bulk[1]);
 			} else {
-				rv = i2c_smbus_read_word_swapped(client,
-						MAX31790_REG_PWMOUT(i));
+				rv = regmap_bulk_read(regmap,
+						      MAX31790_REG_PWMOUT(i),
+						      val_bulk,
+						      2);
 				if (rv < 0)
 					goto abort;
-				data->pwm[i] = rv;
+				data->pwm[i] = BULK_TO_U16(val_bulk[0],
+							   val_bulk[1]);
 
-				rv = i2c_smbus_read_word_swapped(client,
-						MAX31790_REG_TARGET_COUNT(i));
+				rv = regmap_bulk_read(regmap,
+						      MAX31790_REG_TARGET_COUNT(i),
+						      val_bulk,
+						      2);
 				if (rv < 0)
 					goto abort;
-				data->target_count[i] = rv;
+				data->target_count[i] =
+					BULK_TO_U16(val_bulk[0],
+						    val_bulk[1]);
 			}
 		}
 
@@ -191,11 +235,12 @@ static int max31790_write_fan(struct device *dev, u32 attr, int channel,
 			      long val)
 {
 	struct max31790_data *data = dev_get_drvdata(dev);
-	struct i2c_client *client = data->client;
+	struct regmap *regmap = data->regmap;
 	int target_count;
 	int err = 0;
 	u8 bits;
 	int sr;
+	u8 bulk_val[2];
 
 	mutex_lock(&data->update_lock);
 
@@ -207,9 +252,9 @@ static int max31790_write_fan(struct device *dev, u32 attr, int channel,
 			((data->fan_dynamics[channel] &
 			  ~MAX31790_FAN_DYN_SR_MASK) |
 			 (bits << MAX31790_FAN_DYN_SR_SHIFT));
-		err = i2c_smbus_write_byte_data(client,
-					MAX31790_REG_FAN_DYNAMICS(channel),
-					data->fan_dynamics[channel]);
+		err = regmap_write(regmap,
+				   MAX31790_REG_FAN_DYNAMICS(channel),
+				   data->fan_dynamics[channel]);
 		if (err < 0)
 			break;
 
@@ -218,10 +263,13 @@ static int max31790_write_fan(struct device *dev, u32 attr, int channel,
 		target_count = clamp_val(target_count, 0x1, 0x7FF);
 
 		data->target_count[channel] = target_count << 5;
+		bulk_val[0] = U16_MSB(data->target_count[channel]);
+		bulk_val[1] = U16_LSB(data->target_count[channel]);
 
-		err = i2c_smbus_write_word_swapped(client,
+		err = regmap_bulk_write(regmap,
 					MAX31790_REG_TARGET_COUNT(channel),
-					data->target_count[channel]);
+					bulk_val,
+					2);
 		break;
 	default:
 		err = -EOPNOTSUPP;
@@ -287,9 +335,10 @@ static int max31790_write_pwm(struct device *dev, u32 attr, int channel,
 			      long val)
 {
 	struct max31790_data *data = dev_get_drvdata(dev);
-	struct i2c_client *client = data->client;
+	struct regmap *regmap = data->regmap;
 	u8 fan_config;
 	int err = 0;
+	u8 bulk_val[2];
 
 	mutex_lock(&data->update_lock);
 
@@ -300,9 +349,12 @@ static int max31790_write_pwm(struct device *dev, u32 attr, int channel,
 			break;
 		}
 		data->pwm[channel] = val << 8;
-		err = i2c_smbus_write_word_swapped(client,
-						   MAX31790_REG_PWMOUT(channel),
-						   data->pwm[channel]);
+		bulk_val[0] = U16_MSB(data->pwm[channel]);
+		bulk_val[1] = U16_LSB(data->pwm[channel]);
+		err = regmap_bulk_write(regmap,
+					MAX31790_REG_PWMOUT(channel),
+					bulk_val,
+					2);
 		break;
 	case hwmon_pwm_enable:
 		fan_config = data->fan_config[channel];
@@ -321,9 +373,9 @@ static int max31790_write_pwm(struct device *dev, u32 attr, int channel,
 			break;
 		}
 		data->fan_config[channel] = fan_config;
-		err = i2c_smbus_write_byte_data(client,
-					MAX31790_REG_FAN_CONFIG(channel),
-					fan_config);
+		err = regmap_write(regmap,
+				   MAX31790_REG_FAN_CONFIG(channel),
+				   fan_config);
 		break;
 	default:
 		err = -EOPNOTSUPP;
@@ -426,23 +478,25 @@ static const struct hwmon_chip_info max31790_chip_info = {
 	.info = max31790_info,
 };
 
-static int max31790_init_client(struct i2c_client *client,
+static int max31790_init_client(struct regmap *regmap,
 				struct max31790_data *data)
 {
-	int i, rv;
+	int i, rv, val;
 
 	for (i = 0; i < NR_CHANNEL; i++) {
-		rv = i2c_smbus_read_byte_data(client,
-				MAX31790_REG_FAN_CONFIG(i));
+		rv = regmap_read(regmap,
+				 MAX31790_REG_FAN_CONFIG(i),
+				 &val);
 		if (rv < 0)
 			return rv;
-		data->fan_config[i] = rv;
+		data->fan_config[i] = val;
 
-		rv = i2c_smbus_read_byte_data(client,
-				MAX31790_REG_FAN_DYNAMICS(i));
+		rv = regmap_read(regmap,
+				 MAX31790_REG_FAN_DYNAMICS(i),
+				 &val);
 		if (rv < 0)
 			return rv;
-		data->fan_dynamics[i] = rv;
+		data->fan_dynamics[i] = val;
 	}
 
 	return 0;
@@ -464,13 +518,19 @@ static int max31790_probe(struct i2c_client *client)
 	if (!data)
 		return -ENOMEM;
 
-	data->client = client;
 	mutex_init(&data->update_lock);
 
+	data->regmap = devm_regmap_init_i2c(client, &max31790_regmap_config);
+
+	if (IS_ERR(data->regmap)) {
+		dev_err(dev, "failed to allocate register map\n");
+		return PTR_ERR(data->regmap);
+	}
+
 	/*
 	 * Initialize the max31790 chip
 	 */
-	err = max31790_init_client(client, data);
+	err = max31790_init_client(data->regmap, data);
 	if (err)
 		return err;
 
-- 
2.30.1

[PATCH 2/7] hwmon: (max31790) Fix and split pwm*_enable

[Václav Kubernát]

In the old code, pwm*_enable does two things. Firstly, it sets whether
the chip should run in PWM or RPM mode. Secondly, it tells the chip
whether it should monitor fan RPM. However, these two settings aren't
tied together, so they shouldn't be set with a single value. In the new
code, fan*_enable now controls fan RPM monitoring (pwm*_enable no longer
controls that).

According to the sysfs hwmon documentation, pwm*_enable has three
possible values, 0 for "no control / full-speed", 1 for manual mode, and
2+ for automatic. The old code works fine for 1 and 2, but 0 only
differs from 1 in that it just turns off fan speed monitoring. The chip
actually does have a way to turn off fan controls (and only monitor),
but what that does is that it sets PWM to 0% duty cycle (which is the
opposite to full-speed) AND it also turns off fan speed monitoring.
Because of this, I implemented the 0 value by setting PWM mode to 100%.
This method does come with a problem: it is impossible to differentiate
between full-speed and PWM mode just from the values on the chip. The
new code solves this by saving a value indicating whether we're in
full-speed mode. This value is initialized to 0, so full-speed mode
won't persist across reboots.

These two changes are closely connected together, mainly because the
detection of the pwm*_enable value depended on whether fan speed
monitoring is enabled (which is now controlled as written in the first
paragraph).

Signed-off-by: Václav Kubernát <kubernat@cesnet.cz>
---
 Documentation/hwmon/max31790.rst |   8 ++-
 drivers/hwmon/max31790.c         | 107 ++++++++++++++++++++++---------
 2 files changed, 80 insertions(+), 35 deletions(-)

diff --git a/Documentation/hwmon/max31790.rst b/Documentation/hwmon/max31790.rst
index f301385d8cef..8979c8a02cd1 100644
--- a/Documentation/hwmon/max31790.rst
+++ b/Documentation/hwmon/max31790.rst
@@ -34,10 +34,12 @@ also be configured to serve as tachometer inputs.
 Sysfs entries
 -------------
 
-================== === =======================================================
+================== === =============================================================
+fan[1-12]_enable   RW  enable fan speed monitoring
 fan[1-12]_input    RO  fan tachometer speed in RPM
 fan[1-12]_fault    RO  fan experienced fault
 fan[1-6]_target    RW  desired fan speed in RPM
-pwm[1-6]_enable    RW  regulator mode, 0=disabled, 1=manual mode, 2=rpm mode
+pwm[1-6]_enable    RW  regulator mode, 0=full speed, 1=manual (pwm) mode, 2=rpm mode
+                       setting rpm mode sets fan*_enable to 1
 pwm[1-6]           RW  fan target duty cycle (0-255)
-================== === =======================================================
+================== === =============================================================
diff --git a/drivers/hwmon/max31790.c b/drivers/hwmon/max31790.c
index ca413985b5f9..eca5ec615734 100644
--- a/drivers/hwmon/max31790.c
+++ b/drivers/hwmon/max31790.c
@@ -39,6 +39,7 @@
 
 #define FAN_RPM_MIN			120
 #define FAN_RPM_MAX			7864320
+#define MAX_PWM				0XFF80
 
 #define RPM_FROM_REG(reg, sr)		(((reg) >> 4) ? \
 					 ((60 * (sr) * 8192) / ((reg) >> 4)) : \
@@ -79,6 +80,7 @@ struct max31790_data {
 	struct mutex update_lock;
 	bool valid; /* zero until following fields are valid */
 	unsigned long last_updated; /* in jiffies */
+	bool full_speed[NR_CHANNEL];
 
 	/* register values */
 	u8 fan_config[NR_CHANNEL];
@@ -226,6 +228,9 @@ static int max31790_read_fan(struct device *dev, u32 attr, int channel,
 	case hwmon_fan_fault:
 		*val = !!(data->fault_status & (1 << channel));
 		return 0;
+	case hwmon_fan_enable:
+		*val = !!(data->fan_config[channel] & MAX31790_FAN_CFG_TACH_INPUT_EN);
+		return 0;
 	default:
 		return -EOPNOTSUPP;
 	}
@@ -271,6 +276,15 @@ static int max31790_write_fan(struct device *dev, u32 attr, int channel,
 					bulk_val,
 					2);
 		break;
+	case hwmon_fan_enable:
+		if (val == 0)
+			data->fan_config[channel] &= ~MAX31790_FAN_CFG_TACH_INPUT_EN;
+		else
+			data->fan_config[channel] |= MAX31790_FAN_CFG_TACH_INPUT_EN;
+		err = regmap_write(regmap,
+				   MAX31790_REG_FAN_CONFIG(channel),
+				   data->fan_config[channel]);
+		break;
 	default:
 		err = -EOPNOTSUPP;
 		break;
@@ -298,6 +312,11 @@ static umode_t max31790_fan_is_visible(const void *_data, u32 attr, int channel)
 		    !(fan_config & MAX31790_FAN_CFG_TACH_INPUT))
 			return 0644;
 		return 0;
+	case hwmon_fan_enable:
+		if (channel < NR_CHANNEL ||
+		    (fan_config & MAX31790_FAN_CFG_TACH_INPUT))
+			return 0644;
+		return 0;
 	default:
 		return 0;
 	}
@@ -319,12 +338,12 @@ static int max31790_read_pwm(struct device *dev, u32 attr, int channel,
 		*val = data->pwm[channel] >> 8;
 		return 0;
 	case hwmon_pwm_enable:
-		if (fan_config & MAX31790_FAN_CFG_RPM_MODE)
+		if (data->full_speed[channel])
+			*val = 0;
+		else if (fan_config & MAX31790_FAN_CFG_RPM_MODE)
 			*val = 2;
-		else if (fan_config & MAX31790_FAN_CFG_TACH_INPUT_EN)
+		else
 			*val = 1;
-		else
-			*val = 0;
 		return 0;
 	default:
 		return -EOPNOTSUPP;
@@ -344,7 +363,7 @@ static int max31790_write_pwm(struct device *dev, u32 attr, int channel,
 
 	switch (attr) {
 	case hwmon_pwm_input:
-		if (val < 0 || val > 255) {
+		if (data->full_speed[channel] || val < 0 || val > 255) {
 			err = -EINVAL;
 			break;
 		}
@@ -358,16 +377,10 @@ static int max31790_write_pwm(struct device *dev, u32 attr, int channel,
 		break;
 	case hwmon_pwm_enable:
 		fan_config = data->fan_config[channel];
-		if (val == 0) {
-			fan_config &= ~(MAX31790_FAN_CFG_TACH_INPUT_EN |
-					MAX31790_FAN_CFG_RPM_MODE);
-		} else if (val == 1) {
-			fan_config = (fan_config |
-				      MAX31790_FAN_CFG_TACH_INPUT_EN) &
-				     ~MAX31790_FAN_CFG_RPM_MODE;
+		if (val == 0 || val == 1) {
+			fan_config &= ~MAX31790_FAN_CFG_RPM_MODE;
 		} else if (val == 2) {
-			fan_config |= MAX31790_FAN_CFG_TACH_INPUT_EN |
-				      MAX31790_FAN_CFG_RPM_MODE;
+			fan_config |= MAX31790_FAN_CFG_RPM_MODE;
 		} else {
 			err = -EINVAL;
 			break;
@@ -376,6 +389,34 @@ static int max31790_write_pwm(struct device *dev, u32 attr, int channel,
 		err = regmap_write(regmap,
 				   MAX31790_REG_FAN_CONFIG(channel),
 				   fan_config);
+
+		/*
+		 * The chip sets PWM to zero when using its "monitor only" mode
+		 * and 0 means full speed.
+		 */
+		if (val == 0) {
+			data->full_speed[channel] = true;
+			data->pwm[channel] = MAX_PWM;
+			bulk_val[0] = U16_MSB(data->pwm[channel]);
+			bulk_val[1] = U16_LSB(data->pwm[channel]);
+			err = regmap_bulk_write(regmap,
+						MAX31790_REG_PWMOUT(channel),
+						bulk_val,
+						2);
+		} else {
+			data->full_speed[channel] = false;
+		}
+
+		/*
+		 * RPM mode implies enabled TACH input, so enable it in RPM
+		 * mode.
+		 */
+		if (val == 2) {
+			data->fan_config[channel] |= MAX31790_FAN_CFG_TACH_INPUT_EN;
+			err = regmap_write(regmap,
+					   MAX31790_REG_FAN_CONFIG(channel),
+					   data->fan_config[channel]);
+		}
 		break;
 	default:
 		err = -EOPNOTSUPP;
@@ -445,25 +486,25 @@ static umode_t max31790_is_visible(const void *data,
 
 static const struct hwmon_channel_info *max31790_info[] = {
 	HWMON_CHANNEL_INFO(fan,
-			   HWMON_F_INPUT | HWMON_F_TARGET | HWMON_F_FAULT,
-			   HWMON_F_INPUT | HWMON_F_TARGET | HWMON_F_FAULT,
-			   HWMON_F_INPUT | HWMON_F_TARGET | HWMON_F_FAULT,
-			   HWMON_F_INPUT | HWMON_F_TARGET | HWMON_F_FAULT,
-			   HWMON_F_INPUT | HWMON_F_TARGET | HWMON_F_FAULT,
-			   HWMON_F_INPUT | HWMON_F_TARGET | HWMON_F_FAULT,
-			   HWMON_F_INPUT | HWMON_F_FAULT,
-			   HWMON_F_INPUT | HWMON_F_FAULT,
-			   HWMON_F_INPUT | HWMON_F_FAULT,
-			   HWMON_F_INPUT | HWMON_F_FAULT,
-			   HWMON_F_INPUT | HWMON_F_FAULT,
-			   HWMON_F_INPUT | HWMON_F_FAULT),
+		HWMON_F_ENABLE | HWMON_F_INPUT | HWMON_F_TARGET | HWMON_F_FAULT,
+		HWMON_F_ENABLE | HWMON_F_INPUT | HWMON_F_TARGET | HWMON_F_FAULT,
+		HWMON_F_ENABLE | HWMON_F_INPUT | HWMON_F_TARGET | HWMON_F_FAULT,
+		HWMON_F_ENABLE | HWMON_F_INPUT | HWMON_F_TARGET | HWMON_F_FAULT,
+		HWMON_F_ENABLE | HWMON_F_INPUT | HWMON_F_TARGET | HWMON_F_FAULT,
+		HWMON_F_ENABLE | HWMON_F_INPUT | HWMON_F_TARGET | HWMON_F_FAULT,
+		HWMON_F_ENABLE | HWMON_F_INPUT | HWMON_F_FAULT,
+		HWMON_F_ENABLE | HWMON_F_INPUT | HWMON_F_FAULT,
+		HWMON_F_ENABLE | HWMON_F_INPUT | HWMON_F_FAULT,
+		HWMON_F_ENABLE | HWMON_F_INPUT | HWMON_F_FAULT,
+		HWMON_F_ENABLE | HWMON_F_INPUT | HWMON_F_FAULT,
+		HWMON_F_ENABLE | HWMON_F_INPUT | HWMON_F_FAULT),
 	HWMON_CHANNEL_INFO(pwm,
-			   HWMON_PWM_INPUT | HWMON_PWM_ENABLE,
-			   HWMON_PWM_INPUT | HWMON_PWM_ENABLE,
-			   HWMON_PWM_INPUT | HWMON_PWM_ENABLE,
-			   HWMON_PWM_INPUT | HWMON_PWM_ENABLE,
-			   HWMON_PWM_INPUT | HWMON_PWM_ENABLE,
-			   HWMON_PWM_INPUT | HWMON_PWM_ENABLE),
+		HWMON_PWM_INPUT | HWMON_PWM_ENABLE,
+		HWMON_PWM_INPUT | HWMON_PWM_ENABLE,
+		HWMON_PWM_INPUT | HWMON_PWM_ENABLE,
+		HWMON_PWM_INPUT | HWMON_PWM_ENABLE,
+		HWMON_PWM_INPUT | HWMON_PWM_ENABLE,
+		HWMON_PWM_INPUT | HWMON_PWM_ENABLE),
 	NULL
 };
 
@@ -491,6 +532,8 @@ static int max31790_init_client(struct regmap *regmap,
 			return rv;
 		data->fan_config[i] = val;
 
+		data->full_speed[i] = false;
+
 		rv = regmap_read(regmap,
 				 MAX31790_REG_FAN_DYNAMICS(i),
 				 &val);
-- 
2.30.1

[PATCH 3/7] hwmon: (max31790) Allow setting pulses

[Václav Kubernát]

In the old code, the value calculated RPM_FROM_REG is misleading. The
left-hand side of the division is correct (as per the datasheet, page
11). The misleading part is the right-hand side: the datasheet says it
is should be "number of pulses * TACH count". The TACH count is the
value of the register which is a 11-bit left-justified value. This means
that the register value should be shifted by 5 if we want the actual
value. However, in the old code, the value is shifted by 4 with no way
to set the pulses per revolution. This essentially means, that the
default pulses per revolution is 2, because shifting the right-hand side
one less bit means that the final value is doubled by 2. In the end,
what happens is, that the old code works as if fan*_pulses had the
default value of 2 all the time. This is somewhat correct, but in my
opinion the intention isn't entirely clear, at first glance, shifting by
4 instead of 5 seems like a bug (after one checks the datasheet).

Pulses per revolution should be a configurable because otherwise there's
no way to correctly calculate the RPM of the fan. This patch adds the
option to set pulses per revolution.

The hwmon documentation for fan*_pulses says that it shouldn't be
present unless the chip has a register to save this value. This seems
non-sensical, because setting the pulses is essential to properly
calculate RPM. The value is saved inside the driver's data structure.

Signed-off-by: Václav Kubernát <kubernat@cesnet.cz>
---
 Documentation/hwmon/max31790.rst |  1 +
 drivers/hwmon/max31790.c         | 57 +++++++++++++++++++++-----------
 2 files changed, 39 insertions(+), 19 deletions(-)

diff --git a/Documentation/hwmon/max31790.rst b/Documentation/hwmon/max31790.rst
index 8979c8a02cd1..8d86698b25de 100644
--- a/Documentation/hwmon/max31790.rst
+++ b/Documentation/hwmon/max31790.rst
@@ -36,6 +36,7 @@ Sysfs entries
 
 ================== === =============================================================
 fan[1-12]_enable   RW  enable fan speed monitoring
+fan[1-12]_pulses   RW  pulses per fan revolution (default: 2)
 fan[1-12]_input    RO  fan tachometer speed in RPM
 fan[1-12]_fault    RO  fan experienced fault
 fan[1-6]_target    RW  desired fan speed in RPM
diff --git a/drivers/hwmon/max31790.c b/drivers/hwmon/max31790.c
index eca5ec615734..74a81e5e3383 100644
--- a/drivers/hwmon/max31790.c
+++ b/drivers/hwmon/max31790.c
@@ -41,10 +41,12 @@
 #define FAN_RPM_MAX			7864320
 #define MAX_PWM				0XFF80
 
-#define RPM_FROM_REG(reg, sr)		(((reg) >> 4) ? \
-					 ((60 * (sr) * 8192) / ((reg) >> 4)) : \
-					 FAN_RPM_MAX)
-#define RPM_TO_REG(rpm, sr)		((60 * (sr) * 8192) / ((rpm) * 2))
+#define RPM_FROM_REG(reg, sr, pulses) \
+	(((reg) >> 5) ? \
+	 ((60 * (sr) * 8192) / ((reg) >> 5) / (pulses)) : \
+	 FAN_RPM_MAX)
+#define RPM_TO_REG(rpm, sr, pulses) \
+	((60 * (sr) * 8192) / ((rpm) * (pulses)))
 
 #define NR_CHANNEL			6
 
@@ -81,6 +83,7 @@ struct max31790_data {
 	bool valid; /* zero until following fields are valid */
 	unsigned long last_updated; /* in jiffies */
 	bool full_speed[NR_CHANNEL];
+	u8 pulses[NR_CHANNEL];
 
 	/* register values */
 	u8 fan_config[NR_CHANNEL];
@@ -217,12 +220,16 @@ static int max31790_read_fan(struct device *dev, u32 attr, int channel,
 	switch (attr) {
 	case hwmon_fan_input:
 		sr = get_tach_period(data->fan_dynamics[channel]);
-		rpm = RPM_FROM_REG(data->tach[channel], sr);
+		rpm = RPM_FROM_REG(data->tach[channel],
+				   sr,
+				   data->pulses[channel]);
 		*val = rpm;
 		return 0;
 	case hwmon_fan_target:
 		sr = get_tach_period(data->fan_dynamics[channel]);
-		rpm = RPM_FROM_REG(data->target_count[channel], sr);
+		rpm = RPM_FROM_REG(data->target_count[channel],
+				   sr,
+				   data->pulses[channel]);
 		*val = rpm;
 		return 0;
 	case hwmon_fan_fault:
@@ -231,6 +238,9 @@ static int max31790_read_fan(struct device *dev, u32 attr, int channel,
 	case hwmon_fan_enable:
 		*val = !!(data->fan_config[channel] & MAX31790_FAN_CFG_TACH_INPUT_EN);
 		return 0;
+	case hwmon_fan_pulses:
+		*val = data->pulses[channel];
+		return 0;
 	default:
 		return -EOPNOTSUPP;
 	}
@@ -264,7 +274,7 @@ static int max31790_write_fan(struct device *dev, u32 attr, int channel,
 			break;
 
 		sr = get_tach_period(data->fan_dynamics[channel]);
-		target_count = RPM_TO_REG(val, sr);
+		target_count = RPM_TO_REG(val, sr, data->pulses[channel]);
 		target_count = clamp_val(target_count, 0x1, 0x7FF);
 
 		data->target_count[channel] = target_count << 5;
@@ -285,6 +295,9 @@ static int max31790_write_fan(struct device *dev, u32 attr, int channel,
 				   MAX31790_REG_FAN_CONFIG(channel),
 				   data->fan_config[channel]);
 		break;
+	case hwmon_fan_pulses:
+		data->pulses[channel] = val;
+		break;
 	default:
 		err = -EOPNOTSUPP;
 		break;
@@ -317,6 +330,10 @@ static umode_t max31790_fan_is_visible(const void *_data, u32 attr, int channel)
 		    (fan_config & MAX31790_FAN_CFG_TACH_INPUT))
 			return 0644;
 		return 0;
+	case hwmon_fan_pulses:
+		if (channel < NR_CHANNEL)
+			return 0644;
+		return 0;
 	default:
 		return 0;
 	}
@@ -486,18 +503,18 @@ static umode_t max31790_is_visible(const void *data,
 
 static const struct hwmon_channel_info *max31790_info[] = {
 	HWMON_CHANNEL_INFO(fan,
-		HWMON_F_ENABLE | HWMON_F_INPUT | HWMON_F_TARGET | HWMON_F_FAULT,
-		HWMON_F_ENABLE | HWMON_F_INPUT | HWMON_F_TARGET | HWMON_F_FAULT,
-		HWMON_F_ENABLE | HWMON_F_INPUT | HWMON_F_TARGET | HWMON_F_FAULT,
-		HWMON_F_ENABLE | HWMON_F_INPUT | HWMON_F_TARGET | HWMON_F_FAULT,
-		HWMON_F_ENABLE | HWMON_F_INPUT | HWMON_F_TARGET | HWMON_F_FAULT,
-		HWMON_F_ENABLE | HWMON_F_INPUT | HWMON_F_TARGET | HWMON_F_FAULT,
-		HWMON_F_ENABLE | HWMON_F_INPUT | HWMON_F_FAULT,
-		HWMON_F_ENABLE | HWMON_F_INPUT | HWMON_F_FAULT,
-		HWMON_F_ENABLE | HWMON_F_INPUT | HWMON_F_FAULT,
-		HWMON_F_ENABLE | HWMON_F_INPUT | HWMON_F_FAULT,
-		HWMON_F_ENABLE | HWMON_F_INPUT | HWMON_F_FAULT,
-		HWMON_F_ENABLE | HWMON_F_INPUT | HWMON_F_FAULT),
+		HWMON_F_PULSES | HWMON_F_ENABLE | HWMON_F_INPUT | HWMON_F_TARGET | HWMON_F_FAULT,
+		HWMON_F_PULSES | HWMON_F_ENABLE | HWMON_F_INPUT | HWMON_F_TARGET | HWMON_F_FAULT,
+		HWMON_F_PULSES | HWMON_F_ENABLE | HWMON_F_INPUT | HWMON_F_TARGET | HWMON_F_FAULT,
+		HWMON_F_PULSES | HWMON_F_ENABLE | HWMON_F_INPUT | HWMON_F_TARGET | HWMON_F_FAULT,
+		HWMON_F_PULSES | HWMON_F_ENABLE | HWMON_F_INPUT | HWMON_F_TARGET | HWMON_F_FAULT,
+		HWMON_F_PULSES | HWMON_F_ENABLE | HWMON_F_INPUT | HWMON_F_TARGET | HWMON_F_FAULT,
+		HWMON_F_PULSES | HWMON_F_ENABLE | HWMON_F_INPUT | HWMON_F_FAULT,
+		HWMON_F_PULSES | HWMON_F_ENABLE | HWMON_F_INPUT | HWMON_F_FAULT,
+		HWMON_F_PULSES | HWMON_F_ENABLE | HWMON_F_INPUT | HWMON_F_FAULT,
+		HWMON_F_PULSES | HWMON_F_ENABLE | HWMON_F_INPUT | HWMON_F_FAULT,
+		HWMON_F_PULSES | HWMON_F_ENABLE | HWMON_F_INPUT | HWMON_F_FAULT,
+		HWMON_F_PULSES | HWMON_F_ENABLE | HWMON_F_INPUT | HWMON_F_FAULT),
 	HWMON_CHANNEL_INFO(pwm,
 		HWMON_PWM_INPUT | HWMON_PWM_ENABLE,
 		HWMON_PWM_INPUT | HWMON_PWM_ENABLE,
@@ -534,6 +551,8 @@ static int max31790_init_client(struct regmap *regmap,
 
 		data->full_speed[i] = false;
 
+		data->pulses[i] = 2;
+
 		rv = regmap_read(regmap,
 				 MAX31790_REG_FAN_DYNAMICS(i),
 				 &val);
-- 
2.30.1

[PATCH 4/7] hwmon: (max31790) Show 0 RPM/fault when input disabled

[Václav Kubernát]

When fan speed input is disabled, it makes no sense to show values in
fan*_input and fan*_fault.

Signed-off-by: Václav Kubernát <kubernat@cesnet.cz>
---
 drivers/hwmon/max31790.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/hwmon/max31790.c b/drivers/hwmon/max31790.c
index 74a81e5e3383..fde08c95d942 100644
--- a/drivers/hwmon/max31790.c
+++ b/drivers/hwmon/max31790.c
@@ -219,6 +219,11 @@ static int max31790_read_fan(struct device *dev, u32 attr, int channel,
 
 	switch (attr) {
 	case hwmon_fan_input:
+		if (!(data->fan_config[channel] &
+		      MAX31790_FAN_CFG_TACH_INPUT_EN)) {
+			*val = 0;
+			return 0;
+		}
 		sr = get_tach_period(data->fan_dynamics[channel]);
 		rpm = RPM_FROM_REG(data->tach[channel],
 				   sr,
@@ -233,6 +238,11 @@ static int max31790_read_fan(struct device *dev, u32 attr, int channel,
 		*val = rpm;
 		return 0;
 	case hwmon_fan_fault:
+		if (!(data->fan_config[channel] &
+		      MAX31790_FAN_CFG_TACH_INPUT_EN)) {
+			*val = 0;
+			return 0;
+		}
 		*val = !!(data->fault_status & (1 << channel));
 		return 0;
 	case hwmon_fan_enable:
-- 
2.30.1

[PATCH 5/7] hwmon: (max31790) Refactor HWMON_CHANNEL_INFO

[Václav Kubernát]

The line was starting to get a little long.

Signed-off-by: Václav Kubernát <kubernat@cesnet.cz>
---
 drivers/hwmon/max31790.c | 37 +++++++++++++++++++++++++------------
 1 file changed, 25 insertions(+), 12 deletions(-)

diff --git a/drivers/hwmon/max31790.c b/drivers/hwmon/max31790.c
index fde08c95d942..d4f259dd4e19 100644
--- a/drivers/hwmon/max31790.c
+++ b/drivers/hwmon/max31790.c
@@ -56,6 +56,19 @@
 #define U16_MSB(num)			(((num) & 0xFF00) >> 8)
 #define U16_LSB(num)			((num) & 0x00FF)
 
+#define FAN_INFO_1_TO_6 \
+	(HWMON_F_PULSES | \
+	HWMON_F_ENABLE | \
+	HWMON_F_INPUT | \
+	HWMON_F_TARGET | \
+	HWMON_F_FAULT)
+
+#define FAN_INFO_7_TO_12 \
+	(HWMON_F_PULSES | \
+	HWMON_F_ENABLE | \
+	HWMON_F_INPUT | \
+	HWMON_F_FAULT)
+
 static const struct regmap_range max31790_ro_range = {
 	.range_min = MAX31790_REG_TACH_COUNT(0),
 	.range_max = MAX31790_REG_PWMOUT(0) - 1,
@@ -513,18 +526,18 @@ static umode_t max31790_is_visible(const void *data,
 
 static const struct hwmon_channel_info *max31790_info[] = {
 	HWMON_CHANNEL_INFO(fan,
-		HWMON_F_PULSES | HWMON_F_ENABLE | HWMON_F_INPUT | HWMON_F_TARGET | HWMON_F_FAULT,
-		HWMON_F_PULSES | HWMON_F_ENABLE | HWMON_F_INPUT | HWMON_F_TARGET | HWMON_F_FAULT,
-		HWMON_F_PULSES | HWMON_F_ENABLE | HWMON_F_INPUT | HWMON_F_TARGET | HWMON_F_FAULT,
-		HWMON_F_PULSES | HWMON_F_ENABLE | HWMON_F_INPUT | HWMON_F_TARGET | HWMON_F_FAULT,
-		HWMON_F_PULSES | HWMON_F_ENABLE | HWMON_F_INPUT | HWMON_F_TARGET | HWMON_F_FAULT,
-		HWMON_F_PULSES | HWMON_F_ENABLE | HWMON_F_INPUT | HWMON_F_TARGET | HWMON_F_FAULT,
-		HWMON_F_PULSES | HWMON_F_ENABLE | HWMON_F_INPUT | HWMON_F_FAULT,
-		HWMON_F_PULSES | HWMON_F_ENABLE | HWMON_F_INPUT | HWMON_F_FAULT,
-		HWMON_F_PULSES | HWMON_F_ENABLE | HWMON_F_INPUT | HWMON_F_FAULT,
-		HWMON_F_PULSES | HWMON_F_ENABLE | HWMON_F_INPUT | HWMON_F_FAULT,
-		HWMON_F_PULSES | HWMON_F_ENABLE | HWMON_F_INPUT | HWMON_F_FAULT,
-		HWMON_F_PULSES | HWMON_F_ENABLE | HWMON_F_INPUT | HWMON_F_FAULT),
+		FAN_INFO_1_TO_6,
+		FAN_INFO_1_TO_6,
+		FAN_INFO_1_TO_6,
+		FAN_INFO_1_TO_6,
+		FAN_INFO_1_TO_6,
+		FAN_INFO_1_TO_6,
+		FAN_INFO_7_TO_12,
+		FAN_INFO_7_TO_12,
+		FAN_INFO_7_TO_12,
+		FAN_INFO_7_TO_12,
+		FAN_INFO_7_TO_12,
+		FAN_INFO_7_TO_12),
 	HWMON_CHANNEL_INFO(pwm,
 		HWMON_PWM_INPUT | HWMON_PWM_ENABLE,
 		HWMON_PWM_INPUT | HWMON_PWM_ENABLE,
-- 
2.30.1

[PATCH 6/7] hwmon: (max31790) Allow setting fan*_div

[Václav Kubernát]

Right now, the divisor (which determines the speed range) is only set
when in RPM mode. However, the speed range also affects the input RPM,
which means, to get more accurate readings, this speed range needs to be
set.

Signed-off-by: Václav Kubernát <kubernat@cesnet.cz>
---
 Documentation/hwmon/max31790.rst |  1 +
 drivers/hwmon/max31790.c         | 46 +++++++++++++++++++++++++++++++-
 2 files changed, 46 insertions(+), 1 deletion(-)

diff --git a/Documentation/hwmon/max31790.rst b/Documentation/hwmon/max31790.rst
index 8d86698b25de..627816fa45fb 100644
--- a/Documentation/hwmon/max31790.rst
+++ b/Documentation/hwmon/max31790.rst
@@ -39,6 +39,7 @@ fan[1-12]_enable   RW  enable fan speed monitoring
 fan[1-12]_pulses   RW  pulses per fan revolution (default: 2)
 fan[1-12]_input    RO  fan tachometer speed in RPM
 fan[1-12]_fault    RO  fan experienced fault
+fan[1-12]_div      RW  set the measurable speed range, not available in RPM mode
 fan[1-6]_target    RW  desired fan speed in RPM
 pwm[1-6]_enable    RW  regulator mode, 0=full speed, 1=manual (pwm) mode, 2=rpm mode
                        setting rpm mode sets fan*_enable to 1
diff --git a/drivers/hwmon/max31790.c b/drivers/hwmon/max31790.c
index d4f259dd4e19..12eab8817c8a 100644
--- a/drivers/hwmon/max31790.c
+++ b/drivers/hwmon/max31790.c
@@ -57,7 +57,8 @@
 #define U16_LSB(num)			((num) & 0x00FF)
 
 #define FAN_INFO_1_TO_6 \
-	(HWMON_F_PULSES | \
+	(HWMON_F_DIV | \
+	HWMON_F_PULSES | \
 	HWMON_F_ENABLE | \
 	HWMON_F_INPUT | \
 	HWMON_F_TARGET | \
@@ -221,6 +222,26 @@ static u8 bits_for_tach_period(int rpm)
 	return bits;
 }
 
+static int bits_for_speed_range(int speed_range)
+{
+	switch (speed_range) {
+	case 1:
+		return 0x0;
+	case 2:
+		return 0x1;
+	case 4:
+		return 0x2;
+	case 8:
+		return 0x3;
+	case 16:
+		return 0x4;
+	case 32:
+		return 0x5;
+	default:
+		return -1;
+	}
+}
+
 static int max31790_read_fan(struct device *dev, u32 attr, int channel,
 			     long *val)
 {
@@ -264,6 +285,9 @@ static int max31790_read_fan(struct device *dev, u32 attr, int channel,
 	case hwmon_fan_pulses:
 		*val = data->pulses[channel];
 		return 0;
+	case hwmon_fan_div:
+		*val = get_tach_period(data->fan_config[channel]);
+		return 0;
 	default:
 		return -EOPNOTSUPP;
 	}
@@ -321,6 +345,25 @@ static int max31790_write_fan(struct device *dev, u32 attr, int channel,
 	case hwmon_fan_pulses:
 		data->pulses[channel] = val;
 		break;
+	case hwmon_fan_div:
+		if (data->fan_config[channel] & MAX31790_FAN_CFG_RPM_MODE) {
+			err = -EINVAL;
+			break;
+		}
+		sr = bits_for_speed_range(val);
+		if (sr < 0) {
+			err = -EINVAL;
+			break;
+		}
+
+		data->fan_dynamics[channel] =
+			((data->fan_dynamics[channel] &
+			  ~MAX31790_FAN_DYN_SR_MASK) |
+			 (sr << MAX31790_FAN_DYN_SR_SHIFT));
+		err = regmap_write(regmap,
+				   MAX31790_REG_FAN_DYNAMICS(channel),
+				   data->fan_dynamics[channel]);
+		break;
 	default:
 		err = -EOPNOTSUPP;
 		break;
@@ -353,6 +396,7 @@ static umode_t max31790_fan_is_visible(const void *_data, u32 attr, int channel)
 		    (fan_config & MAX31790_FAN_CFG_TACH_INPUT))
 			return 0644;
 		return 0;
+	case hwmon_fan_div:
 	case hwmon_fan_pulses:
 		if (channel < NR_CHANNEL)
 			return 0644;
-- 
2.30.1

[PATCH 7/7] hwmon: (max31790) Update documentation

[Václav Kubernát]

The conditions for fan fault and its connection to the PWM mode are now
documented.

The pwm_rate_of_change and fan_window are now mentioned. According to
our testing with Sunon PF36281BX-000U-S99, these values are crucial in
how RPM mode works and how long it takes for the RPM to stabilize. For
example, setting 5000 RPM (the fan goes up to 23000), the
pwm_rate_of_change needed to be changed to the lowest possible value,
otherwise the chip would just go from pwm 0 to pwm 60 back and forth and
never achieving 5000 RPM (and also signaling fan fault). Based on this
testing, we found out that it the pwm_rate_of_change and fan_window
values need to be changed manually by the user, based on the user's
exact fan configuration.

Signed-off-by: Václav Kubernát <kubernat@cesnet.cz>
---
 Documentation/hwmon/max31790.rst | 48 +++++++++++++++++++++++++++++++-
 1 file changed, 47 insertions(+), 1 deletion(-)

diff --git a/Documentation/hwmon/max31790.rst b/Documentation/hwmon/max31790.rst
index 627816fa45fb..d5ab7caa491a 100644
--- a/Documentation/hwmon/max31790.rst
+++ b/Documentation/hwmon/max31790.rst
@@ -30,6 +30,51 @@ monitoring and control of fan RPM as well as detection of fan failure.
 Six pins are dedicated tachometer inputs. Any of the six PWM outputs can
 also be configured to serve as tachometer inputs.
 
+About pwm[1-6]_enable
+---------------------
+full-speed
+- The chip doesn't have a specific way to set "full speed", so setting pwm[1-6]_enable to 0 is just "set PWM mode with 255 duty cycle".
+
+PWM mode
+- Fan speed is controlled by writing a value to pwm[1-6].
+
+RPM mode
+- Fan speed is controlled by writing a value to fan[1-6]_target.
+
+About fan[1-6]_fault
+--------------------
+In PWM (or full-speed) mode, if the input RPM goes below what is set
+in fan[1-6]_target, fan[1-6]_fault gets set to 1. In other words,
+fan[1-6]_target works as the minimum input RPM before a fan fault goes off.
+
+In RPM mode, fan fault is set when the fan spins "too slowly" (exact
+conditions are in the datasheet). RPM mode depends on four variables:
+
+- target_speed:        This is set by fan[1-6]_target.
+- speed_range:         This is set automatically when setting target_speed or manually by fan[1-12]_div.
+- pwm_rate_of_change:  NOT set by the driver.
+- fan_window:          NOT set by the driver.
+
+The last two values are not set by the driver, because there's no generic way to
+compute them. You should set them manually through i2c (in the bootloader for
+example). Check the datasheet for details. The driver uses `regmap`, so it
+should be easy to read the values of the registers from userspace.
+
+The fan fault value latches. To reset it, set a value to pwm[1-6]
+or fan[1-6]_target.
+
+About fan[1-12]_pulses
+----------------------
+You should set this depending on the fan you use. It affects what values
+are in fan[1-12]_input and also what gets written to fan[1-6]_target.
+
+About fan[1-12]_div
+-------------------
+This value affects the measurable range of the chip. The driver sets this value
+automatically in RPM based on fan[1-6]_target. In PWM mode, you should set this
+value manually based on the details from the datasheet. Setting the speed range
+is disabled while in RPM mode to prevent overwriting the automatically
+calculated value.
 
 Sysfs entries
 -------------
@@ -40,7 +85,8 @@ fan[1-12]_pulses   RW  pulses per fan revolution (default: 2)
 fan[1-12]_input    RO  fan tachometer speed in RPM
 fan[1-12]_fault    RO  fan experienced fault
 fan[1-12]_div      RW  set the measurable speed range, not available in RPM mode
-fan[1-6]_target    RW  desired fan speed in RPM
+fan[1-6]_target    RW  RPM mode = desired fan speed,
+                       PWM mode = minimum fan speed until fault
 pwm[1-6]_enable    RW  regulator mode, 0=full speed, 1=manual (pwm) mode, 2=rpm mode
                        setting rpm mode sets fan*_enable to 1
 pwm[1-6]           RW  fan target duty cycle (0-255)
-- 
2.30.1

Re: [PATCH 3/7] hwmon: (max31790) Allow setting pulses

[Jan Kundrát]

> @@ -285,6 +295,9 @@ static int max31790_write_fan(struct device 
> *dev, u32 attr, int channel,
>  				   MAX31790_REG_FAN_CONFIG(channel),
>  				   data->fan_config[channel]);
>  		break;
> +	case hwmon_fan_pulses:
> +		data->pulses[channel] = val;
> +		break;

This needs input validation, otherwise it's possible to write 0 in there 
and you get a division-by-zero in the kernel context:

[102109.999968] Division by zero in kernel.
[102110.003917] CPU: 1 PID: 27590 Comm: cat Not tainted 5.9.3-cla-cfb #42
[102110.010462] Hardware name: Marvell Armada 380/385 (Device Tree)
[102110.016497] [<c010f16c>] (unwind_backtrace) from [<c010ae40>] 
(show_stack+0x10/0x14)
[102110.024355] [<c010ae40>] (show_stack) from [<c083ba30>] 
(dump_stack+0x94/0xa8)
[102110.031689] [<c083ba30>] (dump_stack) from [<c083a3fc>] 
(Ldiv0+0x8/0x2c)
[102110.038499] [<c083a3fc>] (Ldiv0) from [<c064c1ac>] 
(max31790_read+0x174/0x204)
[102110.045836] [<c064c1ac>] (max31790_read) from [<c0646fdc>] 
(hwmon_attr_show+0x44/0x138)
...

A similar error can also happen when setting the fan speed to 0 RPM. 
That's, however, not an error caused by this patch series AFAIK. I *think* 
that RPM_TO_REG should be changed to check if `rpm` is 0, and if so, set 
the register directly to the maximal value of 0x7ff (in another patch).

With kind regards,
Jan

Re: [PATCH 3/7] hwmon: (max31790) Allow setting pulses

[Václav Kubernát]

Thanks, I will include fixes in v2 of the patches.

By the way, I'd like to mention that Jan is my colleague.

Václav

pá 5. 3. 2021 v 13:08 odesílatel Jan Kundrát <jan.kundrat@cesnet.cz> napsal:
>
> > @@ -285,6 +295,9 @@ static int max31790_write_fan(struct device
> > *dev, u32 attr, int channel,
> >                                  MAX31790_REG_FAN_CONFIG(channel),
> >                                  data->fan_config[channel]);
> >               break;
> > +     case hwmon_fan_pulses:
> > +             data->pulses[channel] = val;
> > +             break;
>
> This needs input validation, otherwise it's possible to write 0 in there
> and you get a division-by-zero in the kernel context:
>
> [102109.999968] Division by zero in kernel.
> [102110.003917] CPU: 1 PID: 27590 Comm: cat Not tainted 5.9.3-cla-cfb #42
> [102110.010462] Hardware name: Marvell Armada 380/385 (Device Tree)
> [102110.016497] [<c010f16c>] (unwind_backtrace) from [<c010ae40>]
> (show_stack+0x10/0x14)
> [102110.024355] [<c010ae40>] (show_stack) from [<c083ba30>]
> (dump_stack+0x94/0xa8)
> [102110.031689] [<c083ba30>] (dump_stack) from [<c083a3fc>]
> (Ldiv0+0x8/0x2c)
> [102110.038499] [<c083a3fc>] (Ldiv0) from [<c064c1ac>]
> (max31790_read+0x174/0x204)
> [102110.045836] [<c064c1ac>] (max31790_read) from [<c0646fdc>]
> (hwmon_attr_show+0x44/0x138)
> ...
>
> A similar error can also happen when setting the fan speed to 0 RPM.
> That's, however, not an error caused by this patch series AFAIK. I *think*
> that RPM_TO_REG should be changed to check if `rpm` is 0, and if so, set
> the register directly to the maximal value of 0x7ff (in another patch).
>
> With kind regards,
> Jan