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hwmon: (pmbus/max31785) Add fan control
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The implementation makes use of the new fan control virtual registers
exposed by the pmbus core. It mixes use of the default implementations
with some overrides via the read/write handlers to handle FAN_COMMAND_1
on the MAX31785, whose definition breaks the value range into various
control bands dependent on RPM or PWM mode.

Signed-off-by: Andrew Jeffery <[email protected]>
Signed-off-by: Guenter Roeck <[email protected]>
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amboar authored and groeck committed Jan 2, 2018
1 parent d206636 commit 56ad86b
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7 changes: 7 additions & 0 deletions Documentation/hwmon/max31785
Original file line number Diff line number Diff line change
Expand Up @@ -32,6 +32,7 @@ Sysfs attributes
fan[1-4]_alarm Fan alarm.
fan[1-4]_fault Fan fault.
fan[1-4]_input Fan RPM.
fan[1-4]_target Fan input target

in[1-6]_crit Critical maximum output voltage
in[1-6]_crit_alarm Output voltage critical high alarm
Expand All @@ -44,6 +45,12 @@ in[1-6]_max_alarm Output voltage high alarm
in[1-6]_min Minimum output voltage
in[1-6]_min_alarm Output voltage low alarm

pwm[1-4] Fan target duty cycle (0..255)
pwm[1-4]_enable 0: Full-speed
1: Manual PWM control
2: Automatic PWM (tach-feedback RPM fan-control)
3: Automatic closed-loop (temp-feedback fan-control)

temp[1-11]_crit Critical high temperature
temp[1-11]_crit_alarm Chip temperature critical high alarm
temp[1-11]_input Measured temperature
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138 changes: 137 additions & 1 deletion drivers/hwmon/pmbus/max31785.c
Original file line number Diff line number Diff line change
Expand Up @@ -20,8 +20,136 @@ enum max31785_regs {

#define MAX31785_NR_PAGES 23

static int max31785_get_pwm(struct i2c_client *client, int page)
{
int rv;

rv = pmbus_get_fan_rate_device(client, page, 0, percent);
if (rv < 0)
return rv;
else if (rv >= 0x8000)
return 0;
else if (rv >= 0x2711)
return 0x2710;

return rv;
}

static int max31785_get_pwm_mode(struct i2c_client *client, int page)
{
int config;
int command;

config = pmbus_read_byte_data(client, page, PMBUS_FAN_CONFIG_12);
if (config < 0)
return config;

command = pmbus_read_word_data(client, page, PMBUS_FAN_COMMAND_1);
if (command < 0)
return command;

if (config & PB_FAN_1_RPM)
return (command >= 0x8000) ? 3 : 2;

if (command >= 0x8000)
return 3;
else if (command >= 0x2711)
return 0;

return 1;
}

static int max31785_read_word_data(struct i2c_client *client, int page,
int reg)
{
int rv;

switch (reg) {
case PMBUS_VIRT_PWM_1:
rv = max31785_get_pwm(client, page);
break;
case PMBUS_VIRT_PWM_ENABLE_1:
rv = max31785_get_pwm_mode(client, page);
break;
default:
rv = -ENODATA;
break;
}

return rv;
}

static inline u32 max31785_scale_pwm(u32 sensor_val)
{
/*
* The datasheet describes the accepted value range for manual PWM as
* [0, 0x2710], while the hwmon pwmX sysfs interface accepts values in
* [0, 255]. The MAX31785 uses DIRECT mode to scale the FAN_COMMAND
* registers and in PWM mode the coefficients are m=1, b=0, R=2. The
* important observation here is that 0x2710 == 10000 == 100 * 100.
*
* R=2 (== 10^2 == 100) accounts for scaling the value provided at the
* sysfs interface into the required hardware resolution, but it does
* not yet yield a value that we can write to the device (this initial
* scaling is handled by pmbus_data2reg()). Multiplying by 100 below
* translates the parameter value into the percentage units required by
* PMBus, and then we scale back by 255 as required by the hwmon pwmX
* interface to yield the percentage value at the appropriate
* resolution for hardware.
*/
return (sensor_val * 100) / 255;
}

static int max31785_pwm_enable(struct i2c_client *client, int page,
u16 word)
{
int config = 0;
int rate;

switch (word) {
case 0:
rate = 0x7fff;
break;
case 1:
rate = pmbus_get_fan_rate_cached(client, page, 0, percent);
if (rate < 0)
return rate;
rate = max31785_scale_pwm(rate);
break;
case 2:
config = PB_FAN_1_RPM;
rate = pmbus_get_fan_rate_cached(client, page, 0, rpm);
if (rate < 0)
return rate;
break;
case 3:
rate = 0xffff;
break;
default:
return -EINVAL;
}

return pmbus_update_fan(client, page, 0, config, PB_FAN_1_RPM, rate);
}

static int max31785_write_word_data(struct i2c_client *client, int page,
int reg, u16 word)
{
switch (reg) {
case PMBUS_VIRT_PWM_1:
return pmbus_update_fan(client, page, 0, 0, PB_FAN_1_RPM,
max31785_scale_pwm(word));
case PMBUS_VIRT_PWM_ENABLE_1:
return max31785_pwm_enable(client, page, word);
default:
break;
}

return -ENODATA;
}

#define MAX31785_FAN_FUNCS \
(PMBUS_HAVE_FAN12 | PMBUS_HAVE_STATUS_FAN12)
(PMBUS_HAVE_FAN12 | PMBUS_HAVE_STATUS_FAN12 | PMBUS_HAVE_PWM12)

#define MAX31785_TEMP_FUNCS \
(PMBUS_HAVE_TEMP | PMBUS_HAVE_STATUS_TEMP)
Expand All @@ -32,11 +160,19 @@ enum max31785_regs {
static const struct pmbus_driver_info max31785_info = {
.pages = MAX31785_NR_PAGES,

.write_word_data = max31785_write_word_data,
.read_word_data = max31785_read_word_data,

/* RPM */
.format[PSC_FAN] = direct,
.m[PSC_FAN] = 1,
.b[PSC_FAN] = 0,
.R[PSC_FAN] = 0,
/* PWM */
.format[PSC_PWM] = direct,
.m[PSC_PWM] = 1,
.b[PSC_PWM] = 0,
.R[PSC_PWM] = 2,
.func[0] = MAX31785_FAN_FUNCS,
.func[1] = MAX31785_FAN_FUNCS,
.func[2] = MAX31785_FAN_FUNCS,
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