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 <[email protected]> --- 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
