hwmon: (pmbus) auto detect pmbus fan pwm mode

PMBus device with fan controls have two possible control modes RPM and
PWM. RPM mode is assumed and FANx_TARGET sensor is always created to
provide read and write access of fan speed control. PWM only devices have
been able to use the FANx_TARGET sensor to read commanded fan speed
correctly because the pmbus core driver caches the write value and return
it when the TARGET sensor is read.

Recent pmbus_core driver change clears the cached value once the write to
FANx_TARGET completes. Read FANx_TARGET sensor now reads from actual PMBus
register. As a result, RPM mode only device, FANx_TARGET sensor always
read 0.

Add detection of current fan control mode during pmbus_identify and set
flag PMBUS_HAVE_PWM12 and/or PMBUS_HAVE_PWM34 if PWM mode is detected.
PWMx and PWMx_ENABLE sensors will be created based on these flags.

Fixes: 1ae5aaf5d1c5 ("hwmon: (pmbus) Clear sensor data after chip write"
Signed-off-by: Zhikui Ren <zhikui.ren@intel.com>

2 files changed, 64 insertions, 2 deletions

diff --git a/drivers/hwmon/pmbus/pmbus.c b/drivers/hwmon/pmbus/pmbus.c
index d0d386990af5..ce2f020f09d7 100644
--- a/drivers/hwmon/pmbus/pmbus.c
+++ b/drivers/hwmon/pmbus/pmbus.c
@@ -29,6 +29,7 @@ static void pmbus_find_sensor_groups(struct i2c_client *client,
 				     struct pmbus_driver_info *info)
 {
 	int page;
+	int fan_mode;
 
 	/* Sensors detected on page 0 only */
 	if (pmbus_check_word_register(client, 0, PMBUS_READ_VIN))
@@ -47,13 +48,20 @@ static void pmbus_find_sensor_groups(struct i2c_client *client,
 		info->func[0] |= PMBUS_HAVE_FAN12;
 		if (pmbus_check_byte_register(client, 0, PMBUS_STATUS_FAN_12))
 			info->func[0] |= PMBUS_HAVE_STATUS_FAN12;
+		fan_mode = pmbus_read_byte_data(client, page, PMBUS_FAN_CONFIG_12);
+		if ((fan_mode & (PB_FAN_1_RPM | PB_FAN_2_RPM)) != (PB_FAN_1_RPM | PB_FAN_2_RPM))
+			info->func[0] |= PMBUS_HAVE_PWM12;
 	}
 	if (pmbus_check_byte_register(client, 0, PMBUS_FAN_CONFIG_34) &&
 	    pmbus_check_word_register(client, 0, PMBUS_READ_FAN_SPEED_3)) {
 		info->func[0] |= PMBUS_HAVE_FAN34;
 		if (pmbus_check_byte_register(client, 0, PMBUS_STATUS_FAN_34))
 			info->func[0] |= PMBUS_HAVE_STATUS_FAN34;
+		fan_mode = pmbus_read_byte_data(client, page, PMBUS_FAN_CONFIG_34);
+		if ((fan_mode & (PB_FAN_1_RPM | PB_FAN_2_RPM)) != (PB_FAN_1_RPM | PB_FAN_2_RPM))
+			info->func[0] |= PMBUS_HAVE_PWM34;
 	}
+
 	if (pmbus_check_word_register(client, 0, PMBUS_READ_TEMPERATURE_1))
 		info->func[0] |= PMBUS_HAVE_TEMP;
 	if (pmbus_check_word_register(client, 0, PMBUS_READ_TEMPERATURE_2))
diff --git a/drivers/hwmon/pmbus/pmbus_core.c b/drivers/hwmon/pmbus/pmbus_core.c
index ec44e4847c48..ceb1b4db985e 100644
--- a/drivers/hwmon/pmbus/pmbus_core.c
+++ b/drivers/hwmon/pmbus/pmbus_core.c
@@ -241,12 +241,32 @@ int pmbus_write_word_data(struct i2c_client *client, int page, u8 reg,
 }
 EXPORT_SYMBOL_NS_GPL(pmbus_write_word_data, PMBUS);
 
+static int pmbus_update_fan_config(struct i2c_client *client, int page, int id,
+				   u8 config, u8 mask)
+{
+	int from;
+	int 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);
+	if (to != from) {
+		rv = pmbus_write_byte_data(client, page, pmbus_fan_config_registers[id], to);
+		if (rv < 0)
+			return rv;
+	}
+	return 0;
+}
 
 static int pmbus_write_virt_reg(struct i2c_client *client, int page, int reg,
 				u16 word)
 {
 	int bit;
 	int id;
+	int config;
 	int rv;
 
 	switch (reg) {
@@ -255,6 +275,18 @@ static int pmbus_write_virt_reg(struct i2c_client *client, int page, int reg,
 		bit = pmbus_fan_rpm_mask[id];
 		rv = pmbus_update_fan(client, page, id, bit, bit, word);
 		break;
+	case PMBUS_VIRT_PWM_1 ... PMBUS_VIRT_PWM_4:
+		id = reg - PMBUS_VIRT_PWM_1;
+		bit = pmbus_fan_rpm_mask[id];
+		/* 0 is pwm mode */
+		rv = pmbus_update_fan(client, page, id, 0, bit, word);
+		break;
+	case PMBUS_VIRT_PWM_ENABLE_1 ... PMBUS_VIRT_PWM_ENABLE_4:
+		id = reg - PMBUS_VIRT_PWM_ENABLE_1;
+		bit = pmbus_fan_rpm_mask[id];
+		config = word ? bit : 0;
+		rv = pmbus_update_fan_config(client, page, id, config, bit);
+		break;
 	default:
 		rv = -ENXIO;
 		break;
@@ -293,8 +325,7 @@ int pmbus_update_fan(struct i2c_client *client, int page, int id,
 	int rv;
 	u8 to;
 
-	from = pmbus_read_byte_data(client, page,
-				    pmbus_fan_config_registers[id]);
+	from = pmbus_read_byte_data(client, page, pmbus_fan_config_registers[id]);
 	if (from < 0)
 		return from;
 
@@ -323,16 +354,39 @@ int pmbus_read_word_data(struct i2c_client *client, int page, int phase, u8 reg)
 }
 EXPORT_SYMBOL_NS_GPL(pmbus_read_word_data, PMBUS);
 
+static int pmbus_get_fan_config(struct i2c_client *client, int page, int id, u8 mask)
+{
+	int from;
+
+	from = pmbus_read_byte_data(client, page, pmbus_fan_config_registers[id]);
+	if (from < 0)
+		return from;
+
+	return from & mask;
+}
+
 static int pmbus_read_virt_reg(struct i2c_client *client, int page, int reg)
 {
 	int rv;
 	int id;
+	int bit;
 
 	switch (reg) {
 	case PMBUS_VIRT_FAN_TARGET_1 ... PMBUS_VIRT_FAN_TARGET_4:
 		id = reg - PMBUS_VIRT_FAN_TARGET_1;
 		rv = pmbus_get_fan_rate_device(client, page, id, rpm);
 		break;
+	case PMBUS_VIRT_PWM_1 ... PMBUS_VIRT_PWM_4:
+		id = reg - PMBUS_VIRT_PWM_1;
+		rv = pmbus_get_fan_rate_device(client, page, id, percent);
+		break;
+	case PMBUS_VIRT_PWM_ENABLE_1 ... PMBUS_VIRT_PWM_ENABLE_4:
+		id = reg - PMBUS_VIRT_PWM_ENABLE_1;
+		bit = pmbus_fan_rpm_mask[id];
+		rv = pmbus_get_fan_config(client, page, id, bit);
+		if (rv >= 0)
+			rv = !rv; /* PWM is enabled when rpm bit is not set (rv = 0) */
+		break;
 	default:
 		rv = -ENXIO;
 		break;