Re: [PATCH v2 2/5] hwmon: (max31790) Fix and split pwm*_enable

["Václav Kubernát" <kubernat@cesnet.cz>]

Okay, no problem, I'll get rid of the full-speed mode (and update the
documentation) in the next version of the patch. Do you think I should
disable the value "0" in pwm*_enable?

Václav

út 20. 4. 2021 v 0:33 odesílatel Guenter Roeck <linux@roeck-us.net> napsal:
>
> On Tue, Apr 13, 2021 at 04:59:45AM +0200, Václav Kubernát wrote:
> > In the old code, pwm*_enable does two things. Firstly, it sets whether
> > the chip should run in PWM or RPM mode. Secondly, it tells the chip
> > whether it should monitor fan RPM. However, these two settings aren't
> > tied together, so they shouldn't be set with a single value. In the new
> > code, fan*_enable now controls fan RPM monitoring (pwm*_enable no longer
> > controls that).
> >
> > According to the sysfs hwmon documentation, pwm*_enable has three
> > possible values, 0 for "no control / full-speed", 1 for manual mode, and
> > 2+ for automatic. The old code works fine for 1 and 2, but 0 only
> > differs from 1 in that it just turns off fan speed monitoring. The chip
> > actually does have a way to turn off fan controls (and only monitor),
> > but what that does is that it sets PWM to 0% duty cycle (which is the
> > opposite to full-speed) AND it also turns off fan speed monitoring.
> > Because of this, I implemented the 0 value by setting PWM mode to 100%.
> > This method does come with a problem: it is impossible to differentiate
> > between full-speed and PWM mode just from the values on the chip. The
> > new code solves this by saving a value indicating whether we're in
> > full-speed mode. This value is initialized to 0, so full-speed mode
> > won't persist across reboots.
> >
> I don't think this is a good idea, sorry. It is not just a problem across
> reboots, but also when unloading and reloading the driver. I think we
> should stick with chip capabilities and adjust the documentation
> accordingly.
>
> Guenter
>
> > These two changes are closely connected together, mainly because the
> > detection of the pwm*_enable value depended on whether fan speed
> > monitoring is enabled (which is now controlled as written in the first
> > paragraph).
> >
> > Signed-off-by: Václav Kubernát <kubernat@cesnet.cz>
> > ---
> >  Documentation/hwmon/max31790.rst |  8 +--
> >  drivers/hwmon/max31790.c         | 87 ++++++++++++++++++++++----------
> >  2 files changed, 66 insertions(+), 29 deletions(-)
> >
> > diff --git a/Documentation/hwmon/max31790.rst b/Documentation/hwmon/max31790.rst
> > index f301385d8cef..8979c8a02cd1 100644
> > --- a/Documentation/hwmon/max31790.rst
> > +++ b/Documentation/hwmon/max31790.rst
> > @@ -34,10 +34,12 @@ also be configured to serve as tachometer inputs.
> >  Sysfs entries
> >  -------------
> >
> > -================== === =======================================================
> > +================== === =============================================================
> > +fan[1-12]_enable   RW  enable fan speed monitoring
> >  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
> > -pwm[1-6]_enable    RW  regulator mode, 0=disabled, 1=manual mode, 2=rpm mode
> > +pwm[1-6]_enable    RW  regulator mode, 0=full speed, 1=manual (pwm) mode, 2=rpm mode
> > +                       setting rpm mode sets fan*_enable to 1
> >  pwm[1-6]           RW  fan target duty cycle (0-255)
> > -================== === =======================================================
> > +================== === =============================================================
> > diff --git a/drivers/hwmon/max31790.c b/drivers/hwmon/max31790.c
> > index e3765ce4444a..ecdd55e12ffe 100644
> > --- a/drivers/hwmon/max31790.c
> > +++ b/drivers/hwmon/max31790.c
> > @@ -39,6 +39,7 @@
> >
> >  #define FAN_RPM_MIN                  120
> >  #define FAN_RPM_MAX                  7864320
> > +#define MAX_PWM                              0XFF80
> >
> >  #define RPM_FROM_REG(reg, sr)                (((reg) >> 4) ? \
> >                                        ((60 * (sr) * 8192) / ((reg) >> 4)) : \
> > @@ -90,6 +91,7 @@ struct max31790_data {
> >       struct regmap *regmap;
> >
> >       struct mutex update_lock;
> > +     bool full_speed[NR_CHANNEL];
> >       u8 fan_config[NR_CHANNEL];
> >       u8 fan_dynamics[NR_CHANNEL];
> >  };
> > @@ -191,6 +193,9 @@ static int max31790_read_fan(struct device *dev, u32 attr, int channel,
> >               else
> >                       *val = !!(fault & (1 << channel));
> >               return 0;
> > +     case hwmon_fan_enable:
> > +             *val = !!(data->fan_config[channel] & MAX31790_FAN_CFG_TACH_INPUT_EN);
> > +             return 0;
> >       default:
> >               return -EOPNOTSUPP;
> >       }
> > @@ -233,6 +238,15 @@ static int max31790_write_fan(struct device *dev, u32 attr, int channel,
> >                                    MAX31790_REG_TARGET_COUNT(channel),
> >                                    target_count);
> >               break;
> > +     case hwmon_fan_enable:
> > +             if (val == 0)
> > +                     data->fan_config[channel] &= ~MAX31790_FAN_CFG_TACH_INPUT_EN;
> > +             else
> > +                     data->fan_config[channel] |= MAX31790_FAN_CFG_TACH_INPUT_EN;
> > +             err = regmap_write(regmap,
> > +                                MAX31790_REG_FAN_CONFIG(channel),
> > +                                data->fan_config[channel]);
> > +             break;
> >       default:
> >               err = -EOPNOTSUPP;
> >               break;
> > @@ -260,6 +274,11 @@ 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_enable:
> > +             if (channel < NR_CHANNEL ||
> > +                 (fan_config & MAX31790_FAN_CFG_TACH_INPUT))
> > +                     return 0644;
> > +             return 0;
> >       default:
> >               return 0;
> >       }
> > @@ -281,12 +300,12 @@ static int max31790_read_pwm(struct device *dev, u32 attr, int channel,
> >               *val = read >> 8;
> >               return 0;
> >       case hwmon_pwm_enable:
> > -             if (data->fan_config[channel] & MAX31790_FAN_CFG_RPM_MODE)
> > +             if (data->full_speed[channel])
> > +                     *val = 0;
> > +             else if (data->fan_config[channel] & MAX31790_FAN_CFG_RPM_MODE)
> >                       *val = 2;
> > -             else if (data->fan_config[channel] & MAX31790_FAN_CFG_TACH_INPUT_EN)
> > +             else
> >                       *val = 1;
> > -             else
> > -                     *val = 0;
> >               return 0;
> >       default:
> >               return -EOPNOTSUPP;
> > @@ -305,28 +324,42 @@ static int max31790_write_pwm(struct device *dev, u32 attr, int channel,
> >
> >       switch (attr) {
> >       case hwmon_pwm_input:
> > -             if (val < 0 || val > 255) {
> > +             if (data->full_speed[channel] || val < 0 || val > 255) {
> >                       err = -EINVAL;
> >                       break;
> >               }
> > +
> >               err = write_reg_word(regmap, MAX31790_REG_PWMOUT(channel), val << 8);
> >               break;
> >       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);
> > -             } else if (val == 1) {
> > -                     fan_config = (fan_config |
> > -                                   MAX31790_FAN_CFG_TACH_INPUT_EN) &
> > -                                  ~MAX31790_FAN_CFG_RPM_MODE;
> > +             if (val == 0 || val == 1) {
> > +                     fan_config &= ~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_RPM_MODE;
> >               } else {
> >                       err = -EINVAL;
> >                       break;
> >               }
> > +
> > +             /*
> > +              * The chip sets PWM to zero when using its "monitor only" mode
> > +              * and 0 means full speed.
> > +              */
> > +             if (val == 0) {
> > +                     data->full_speed[channel] = true;
> > +                     err = write_reg_word(regmap, MAX31790_REG_PWMOUT(channel), MAX_PWM);
> > +             } else {
> > +                     data->full_speed[channel] = false;
> > +             }
> > +
> > +             /*
> > +              * RPM mode implies enabled TACH input, so enable it in RPM
> > +              * mode.
> > +              */
> > +             if (val == 2)
> > +                     fan_config |= MAX31790_FAN_CFG_TACH_INPUT_EN;
> > +
> >               data->fan_config[channel] = fan_config;
> >               err = regmap_write(regmap,
> >                                  MAX31790_REG_FAN_CONFIG(channel),
> > @@ -400,18 +433,18 @@ static umode_t max31790_is_visible(const void *data,
> >
> >  static const struct hwmon_channel_info *max31790_info[] = {
> >       HWMON_CHANNEL_INFO(fan,
> > -                        HWMON_F_INPUT | HWMON_F_TARGET | HWMON_F_FAULT,
> > -                        HWMON_F_INPUT | HWMON_F_TARGET | HWMON_F_FAULT,
> > -                        HWMON_F_INPUT | HWMON_F_TARGET | HWMON_F_FAULT,
> > -                        HWMON_F_INPUT | HWMON_F_TARGET | HWMON_F_FAULT,
> > -                        HWMON_F_INPUT | HWMON_F_TARGET | HWMON_F_FAULT,
> > -                        HWMON_F_INPUT | HWMON_F_TARGET | HWMON_F_FAULT,
> > -                        HWMON_F_INPUT | HWMON_F_FAULT,
> > -                        HWMON_F_INPUT | HWMON_F_FAULT,
> > -                        HWMON_F_INPUT | HWMON_F_FAULT,
> > -                        HWMON_F_INPUT | HWMON_F_FAULT,
> > -                        HWMON_F_INPUT | HWMON_F_FAULT,
> > -                        HWMON_F_INPUT | 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_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_CHANNEL_INFO(pwm,
> >                          HWMON_PWM_INPUT | HWMON_PWM_ENABLE,
> >                          HWMON_PWM_INPUT | HWMON_PWM_ENABLE,
> > @@ -448,6 +481,8 @@ static int max31790_init_client(struct regmap *regmap,
> >               if (rv < 0)
> >                       return rv;
> >               data->fan_dynamics[i] = rv;
> > +
> > +             data->full_speed[i] = false;
> >       }
> >
> >       return 0;