hwmon: (max31790) Add support for fanX_min attributes

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>

diff --git a/Documentation/hwmon/max31790.rst b/Documentation/hwmon/max31790.rst
index b43aa32813fda88e9dafee3f47dd19ba1d7c5ab0..9225c2a78b6831737fd3411c8096330b2ea59b92 100644 (file)
--- 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 91fe419b596cd7a0bd4d52fdcbb32111c53d9e37..db97ee99515a751dec2cabf470ff85cd5a87f31b 100644 (file)
--- 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,