Re: [PATCH] hwmon: (max31790) add fanN_enable

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On Mon, Aug 29, 2022 at 11:08 AM Guenter Roeck <linux@xxxxxxxxxxxx> wrote:
>
> On 8/29/22 10:15, Justin Ledford wrote:
> > On Mon, Aug 29, 2022 at 9:11 AM Guenter Roeck <linux@xxxxxxxxxxxx> wrote:
> >>
> >> On Mon, Aug 29, 2022 at 08:09:21AM -0700, Justin Ledford wrote:
> >>> The tach input isn't enabled in the device by default. So the only way
> >>> to start using the fan input sensors is to set the regulator mode
> >>> through the driver to RPM mode and then back to whatever mode you
> >>> actually want to use. The I2C interface to the device doesn't couple
> >>> the tach input to the regulator mode so I don't think it makes sense
> >>> for the driver to do this either.
> >>>
> >> Please don't top-post.
> >>
> >> The above does not answer my question why fan_config[] wound need to
> >> be updated repeatedly.
> >>
> >> Guenter
> >>
> >>> On Mon, Aug 29, 2022 at 6:20 AM Guenter Roeck <linux@xxxxxxxxxxxx> wrote:
> >>>>
> >>>> On Mon, Aug 29, 2022 at 02:43:51AM +0000, Justin Ledford wrote:
> >>>>> The MAX31790 has a tach input enable bit in each fan's configuration
> >>>>> register. This is only enabled by the driver if RPM mode is selected,
> >>>>> but the driver doesn't provide a way to independently enable tachometer
> >>>>> input regardless of the regulator mode.
> >>>>>
> >>>>> By adding the fanN_enable sysfs files, we can decouple the tach input
> >>>>> from the regulator mode. Also update the documentation.
> >>>>>
> >>>>> Signed-off-by: Justin Ledford <justinledford@xxxxxxxxxx>
> >>>>> ---
> >>>>>   Documentation/hwmon/max31790.rst |  1 +
> >>>>>   drivers/hwmon/max31790.c         | 44 +++++++++++++++++++++++++++-----
> >>>>>   2 files changed, 38 insertions(+), 7 deletions(-)
> >>>>>
> >>>>> diff --git a/Documentation/hwmon/max31790.rst b/Documentation/hwmon/max31790.rst
> >>>>> index 7b097c3b9b90..33c5c7330efc 100644
> >>>>> --- a/Documentation/hwmon/max31790.rst
> >>>>> +++ b/Documentation/hwmon/max31790.rst
> >>>>> @@ -38,6 +38,7 @@ Sysfs entries
> >>>>>   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
> >>>>> +fan[1-6]_enable    RW  enable or disable the tachometer input
> >>>>>   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,
> >>>>>                          write: target pwm duty cycle (0-255)
> >>>>> diff --git a/drivers/hwmon/max31790.c b/drivers/hwmon/max31790.c
> >>>>> index 7e9362f6dc29..3ae02be4b41e 100644
> >>>>> --- a/drivers/hwmon/max31790.c
> >>>>> +++ b/drivers/hwmon/max31790.c
> >>>>> @@ -118,6 +118,12 @@ static struct max31790_data *max31790_update_device(struct device *dev)
> >>>>>                                        goto abort;
> >>>>>                                data->target_count[i] = rv;
> >>>>>                        }
> >>>>> +
> >>>>> +                     rv = i2c_smbus_read_byte_data(client,
> >>>>> +                                     MAX31790_REG_FAN_CONFIG(i));
> >>>>> +                     if (rv < 0)
> >>>>> +                             goto abort;
> >>>>> +                     data->fan_config[i] = rv;
> >>>>
> >>>> Why is this needed ?
> >>>>
> >>>> Guenter
> >>>>
> >
> > This is needed in case the fan_config is changed outside the driver
> > with something like i2ctransfer, so that the driver reports the actual
> > state of the device, rather than the state at the time of the last
> > write originating from the driver.
> >
>
> That is not a concern or valid argument. With such an argument,
> not a single I2C (or, for that matter, any other) register would
> be cacheable, and much of the caching code in the kernel would
> not work. Anyone hacking around any driver in the system would
> be on their own. One could even argue that such hacking should
> be undone if possible because it may have severe and unexpected
> impact on any driver operation.
>
> Guenter
>
Thank you for the feedback, that makes sense. I will send an updated
patch with this chunk removed.
> >>>>>                }
> >>>>>
> >>>>>                data->last_updated = jiffies;
> >>>>> @@ -202,6 +208,9 @@ static int max31790_read_fan(struct device *dev, u32 attr, int channel,
> >>>>>                }
> >>>>>                mutex_unlock(&data->update_lock);
> >>>>>                return 0;
> >>>>> +     case hwmon_fan_enable:
> >>>>> +             *val = !!(data->fan_config[channel] & MAX31790_FAN_CFG_TACH_INPUT_EN);
> >>>>> +             return 0;
> >>>>>        default:
> >>>>>                return -EOPNOTSUPP;
> >>>>>        }
> >>>>> @@ -214,7 +223,7 @@ static int max31790_write_fan(struct device *dev, u32 attr, int channel,
> >>>>>        struct i2c_client *client = data->client;
> >>>>>        int target_count;
> >>>>>        int err = 0;
> >>>>> -     u8 bits;
> >>>>> +     u8 bits, fan_config;
> >>>>>        int sr;
> >>>>>
> >>>>>        mutex_lock(&data->update_lock);
> >>>>> @@ -243,6 +252,23 @@ static int max31790_write_fan(struct device *dev, u32 attr, int channel,
> >>>>>                                        MAX31790_REG_TARGET_COUNT(channel),
> >>>>>                                        data->target_count[channel]);
> >>>>>                break;
> >>>>> +     case hwmon_fan_enable:
> >>>>> +             fan_config = data->fan_config[channel];
> >>>>> +             if (val == 0) {
> >>>>> +                     fan_config &= ~MAX31790_FAN_CFG_TACH_INPUT_EN;
> >>>>> +             } else if (val == 1) {
> >>>>> +                     fan_config |= MAX31790_FAN_CFG_TACH_INPUT_EN;
> >>>>> +             } else {
> >>>>> +                     err = -EINVAL;
> >>>>> +                     break;
> >>>>> +             }
> >>>>> +             if (fan_config != data->fan_config[channel]) {
> >>>>> +                     err = i2c_smbus_write_byte_data(client, MAX31790_REG_FAN_CONFIG(channel),
> >>>>> +                                                     fan_config);
> >>>>> +                     if (!err)
> >>>>> +                             data->fan_config[channel] = fan_config;
> >>>>> +             }
> >>>>> +             break;
> >>>>>        default:
> >>>>>                err = -EOPNOTSUPP;
> >>>>>                break;
> >>>>> @@ -270,6 +296,10 @@ 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_enable:
> >>>>> +             if (channel < NR_CHANNEL)
> >>>>> +                     return 0644;
> >>>>> +             return 0;
> >>>>>        default:
> >>>>>                return 0;
> >>>>>        }
> >>>>> @@ -423,12 +453,12 @@ 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_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_INPUT | HWMON_F_FAULT,
> >>>>>                           HWMON_F_INPUT | HWMON_F_FAULT,
> >>>>> --
> >>>>> 2.37.2.672.g94769d06f0-goog
> >>>>>
>



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