[PATCH 7/7] hwmon: (max31790) Add support for fanX_min attributes

Guenter Roeck
2021-05-26T15:40:50Z

The minimum fan speed is closely correlated to the target fan speed.
The correlation depends on the pwm mode. It is essential to be able
to read and to set it to be able to control when a channel will report
a fan fault.

Since the minimum fan speed also applies to channels 7..12, make it
visible but read-only for those channels as well.

Cc: Jan Kundrát <jan.kundrat@cesnet.cz>
Cc: Václav Kubernát <kubernat@cesnet.cz>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
---
Documentation/hwmon/max31790.rst | 9 ++++
drivers/hwmon/max31790.c | 70 ++++++++++++++++++++++++--------
2 files changed, 61 insertions(+), 18 deletions(-)

diff --git a/Documentation/hwmon/max31790.rst b/Documentation/hwmon/max31790.rst
index b43aa32813fd..9225c2a78b68 100644
--- a/Documentation/hwmon/max31790.rst
+++ b/Documentation/hwmon/max31790.rst
@@ -40,6 +40,15 @@ fan[1-12]_enable RW 0=disable fan speed monitoring, 1=enable fan speed monito
channels, the value matches the value of the primary channel.
fan[1-12]_input RO fan tachometer speed in RPM
fan[1-12]_fault RO fan experienced fault
+fan[1-12]_min RW minimum fan speed in RPM. Equivalent to target fan speed
+ in PWM mode and if PWM support is disabled for a channel.
+ Equivalent to half the target fan speed in RPM mode.
+ The value is RO for companion channels (7-12). For those
+ channels, the value matches the value of the primary channel.
+ Note: In RPM mode, if the pwm duty cycle is 100%, the
+ minimum fan speed is equivalent to the target fan speed,
+ and the chip will report a fault condition if the fan
+ speed is below the target fan speed.
fan[1-6]_target RW desired fan speed in RPM
pwm[1-6]_enable RW regulator mode, 0=disabled (duty cycle=0%), 1=manual mode, 2=rpm mode
pwm[1-6] RW read: current pwm duty cycle,
diff --git a/drivers/hwmon/max31790.c b/drivers/hwmon/max31790.c
index 91fe419b596c..db97ee99515a 100644
--- a/drivers/hwmon/max31790.c
+++ b/drivers/hwmon/max31790.c
@@ -111,13 +111,11 @@ static struct max31790_data *max31790_update_device(struct device *dev)
if (rv < 0)
goto abort;
data->pwm[i] = rv;
-
- rv = i2c_smbus_read_word_swapped(client,
- MAX31790_REG_TARGET_COUNT(i));
- if (rv < 0)
- goto abort;
- data->target_count[i] = rv;
}
+ rv = i2c_smbus_read_word_swapped(client, MAX31790_REG_TARGET_COUNT(i));
+ if (rv < 0)
+ goto abort;
+ data->target_count[i] = rv;
}

data->last_updated = jiffies;
@@ -183,6 +181,21 @@ static int max31790_read_fan(struct device *dev, u32 attr, int channel,
rpm = RPM_FROM_REG(data->tach[channel], sr);
*val = rpm;
return 0;
+ case hwmon_fan_min:
+ channel %= NR_CHANNEL;
+ sr = get_tach_period(data->fan_dynamics[channel]);
+ if (!(data->fan_config[channel] & MAX31790_FAN_CFG_RPM_MODE) ||
+ (data->fan_config[channel] & MAX31790_FAN_CFG_TACH_INPUT)) {
+ /* pwm mode: target == min */
+ rpm = RPM_FROM_REG(data->target_count[channel], sr);
+ } else {
+ /* rpm mode: min tach count is twice target count */
+ u16 tach = min(data->target_count[channel] * 2, FAN_COUNT_REG_MAX);
+
+ rpm = RPM_FROM_REG(tach, sr);
+ }
+ *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);
@@ -243,6 +256,20 @@ static int max31790_write_fan(struct device *dev, u32 attr, int channel,
data->fan_config[channel] = config;
}
break;
+ case hwmon_fan_min:
+ /*
+ * The minimum fan speed is the same as the target fan speed in
+ * PWM mode and if a PWM channel is disabled, or it is half the
+ * target fan speed in RPM mode.
+ */
+ if (!(data->fan_config[channel] & MAX31790_FAN_CFG_TACH_INPUT) &&
+ (data->fan_config[channel] & MAX31790_FAN_CFG_RPM_MODE)) {
+ /* partial clamp to avoid overflow */
+ if (val > FAN_RPM_MAX / 2)
+ val = FAN_RPM_MAX / 2;
+ val *= 2;
+ }
+ fallthrough;
case hwmon_fan_target:
val = clamp_val(val, FAN_RPM_MIN, FAN_RPM_MAX);
bits = bits_for_tach_period(val);
@@ -282,6 +309,7 @@ static umode_t max31790_fan_is_visible(const void *_data, u32 attr, int channel)
u8 fan_config = data->fan_config[channel % NR_CHANNEL];

switch (attr) {
+ case hwmon_fan_min:
case hwmon_fan_enable:
if (channel < NR_CHANNEL)
return 0644;
@@ -452,18 +480,24 @@ 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_ENABLE | HWMON_F_INPUT | HWMON_F_MIN | HWMON_F_TARGET |
+ HWMON_F_FAULT,
+ HWMON_F_ENABLE | HWMON_F_INPUT | HWMON_F_MIN | HWMON_F_TARGET |
+ HWMON_F_FAULT,
+ HWMON_F_ENABLE | HWMON_F_INPUT | HWMON_F_MIN | HWMON_F_TARGET |
+ HWMON_F_FAULT,
+ HWMON_F_ENABLE | HWMON_F_INPUT | HWMON_F_MIN | HWMON_F_TARGET |
+ HWMON_F_FAULT,
+ HWMON_F_ENABLE | HWMON_F_INPUT | HWMON_F_MIN | HWMON_F_TARGET |
+ HWMON_F_FAULT,
+ HWMON_F_ENABLE | HWMON_F_INPUT | HWMON_F_MIN | HWMON_F_TARGET |
+ HWMON_F_FAULT,
+ HWMON_F_ENABLE | HWMON_F_INPUT | HWMON_F_MIN | HWMON_F_FAULT,
+ HWMON_F_ENABLE | HWMON_F_INPUT | HWMON_F_MIN | HWMON_F_FAULT,
+ HWMON_F_ENABLE | HWMON_F_INPUT | HWMON_F_MIN | HWMON_F_FAULT,
+ HWMON_F_ENABLE | HWMON_F_INPUT | HWMON_F_MIN | HWMON_F_FAULT,
+ HWMON_F_ENABLE | HWMON_F_INPUT | HWMON_F_MIN | HWMON_F_FAULT,
+ HWMON_F_ENABLE | HWMON_F_INPUT | HWMON_F_MIN | HWMON_F_FAULT),
HWMON_CHANNEL_INFO(pwm,
HWMON_PWM_INPUT | HWMON_PWM_ENABLE,
HWMON_PWM_INPUT | HWMON_PWM_ENABLE,
--
2.25.1