From 148c847c9e5a54b99850617bf9c143af9a344f92 Mon Sep 17 00:00:00 2001 From: Guenter Roeck Date: Wed, 26 May 2021 08:40:18 -0700 Subject: hwmon: (max31790) Fix pwmX_enable attributes MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit pwmX_enable supports three possible values: 0: Fan control disabled. Duty cycle is fixed to 0% 1: Fan control enabled, pwm mode. Duty cycle is determined by values written into Target Duty Cycle registers. 2: Fan control enabled, rpm mode Duty cycle is adjusted such that fan speed matches the values in Target Count registers The current code does not do this; instead, it mixes pwm control configuration with fan speed monitoring configuration. Worse, it reports that pwm control would be disabled (pwmX_enable==0) when it is in fact enabled in pwm mode. Part of the problem may be that the chip sets the "TACH input enable" bit on its own whenever the mode bit is set to RPM mode, but that doesn't mean that "TACH input enable" accurately reflects the pwm mode. Fix it up and only handle pwm control with the pwmX_enable attributes. In the documentation, clarify that disabling pwm control (pwmX_enable=0) sets the pwm duty cycle to 0%. In the code, explain why TACH_INPUT_EN is set together with RPM_MODE. While at it, only update the configuration register if the configuration has changed, and only update the cached configuration if updating the chip configuration was successful. Cc: Jan Kundrát Cc: Václav Kubernát Signed-off-by: Guenter Roeck Tested-by: Václav Kubernát Reviewed-by: Jan Kundrát Link: https://lore.kernel.org/r/20210526154022.3223012-4-linux@roeck-us.net --- drivers/hwmon/max31790.c | 41 ++++++++++++++++++++++++++--------------- 1 file changed, 26 insertions(+), 15 deletions(-) (limited to 'drivers/hwmon/max31790.c') diff --git a/drivers/hwmon/max31790.c b/drivers/hwmon/max31790.c index 693497e09ac0..67677c437768 100644 --- a/drivers/hwmon/max31790.c +++ b/drivers/hwmon/max31790.c @@ -27,6 +27,7 @@ /* Fan Config register bits */ #define MAX31790_FAN_CFG_RPM_MODE 0x80 +#define MAX31790_FAN_CFG_CTRL_MON 0x10 #define MAX31790_FAN_CFG_TACH_INPUT_EN 0x08 #define MAX31790_FAN_CFG_TACH_INPUT 0x01 @@ -271,12 +272,12 @@ 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 (fan_config & MAX31790_FAN_CFG_CTRL_MON) + *val = 0; + else if (fan_config & MAX31790_FAN_CFG_RPM_MODE) *val = 2; - else if (fan_config & MAX31790_FAN_CFG_TACH_INPUT_EN) - *val = 1; else - *val = 0; + *val = 1; return 0; default: return -EOPNOTSUPP; @@ -307,23 +308,33 @@ static int max31790_write_pwm(struct device *dev, u32 attr, int channel, 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); + fan_config |= MAX31790_FAN_CFG_CTRL_MON; + /* + * Disable RPM mode; otherwise disabling fan speed + * monitoring is not possible. + */ + fan_config &= ~MAX31790_FAN_CFG_RPM_MODE; } else if (val == 1) { - fan_config = (fan_config | - MAX31790_FAN_CFG_TACH_INPUT_EN) & - ~MAX31790_FAN_CFG_RPM_MODE; + fan_config &= ~(MAX31790_FAN_CFG_CTRL_MON | 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_CTRL_MON; + /* + * The chip sets MAX31790_FAN_CFG_TACH_INPUT_EN on its + * own if MAX31790_FAN_CFG_RPM_MODE is set. + * Do it here as well to reflect the actual register + * value in the cache. + */ + fan_config |= (MAX31790_FAN_CFG_RPM_MODE | MAX31790_FAN_CFG_TACH_INPUT_EN); } else { err = -EINVAL; break; } - data->fan_config[channel] = fan_config; - err = i2c_smbus_write_byte_data(client, - MAX31790_REG_FAN_CONFIG(channel), - fan_config); + if (fan_config != data->fan_config[channel]) { + err = i2c_smbus_write_byte_data(client, MAX31790_REG_FAN_CONFIG(channel), + fan_config); + if (!err) + data->fan_config[channel] = fan_config; + } break; default: err = -EOPNOTSUPP; -- cgit v1.2.3