On Mon, Aug 12, 2024 at 01:45:38PM +0530, Raag Jadav wrote:
> Add hwmon support for fan1_input attribute, which will expose fan speed
> in RPM. With this in place we can monitor fan speed using lm-sensors tool.
>
> $ sensors
> i915-pci-0300
> Adapter: PCI adapter
> in0: 653.00 mV
> fan1: 3833 RPM
> power1: N/A (max = 43.00 W)
> energy1: 32.02 kJ
...
> +static int
> +hwm_fan_read(struct hwm_drvdata *ddat, u32 attr, long *val)
> +{
> + struct i915_hwmon *hwmon = ddat->hwmon;
> + struct hwm_fan_info *fi = &ddat->fi;
> + u64 rotations, time_now, time;
> + intel_wakeref_t wakeref;
> + u32 reg_val, pulses;
> + int ret = 0;
> +
> + if (attr != hwmon_fan_input)
> + return -EOPNOTSUPP;
> +
> + wakeref = intel_runtime_pm_get(ddat->uncore->rpm);
> + mutex_lock(&hwmon->hwmon_lock);
> +
> + reg_val = intel_uncore_read(ddat->uncore, hwmon->rg.fan_speed);
> + time_now = get_jiffies_64();
> + /* Handle HW register overflow */
> + if (reg_val >= fi->reg_val_prev)
> + pulses = reg_val - fi->reg_val_prev;
> + else
> + pulses = UINT_MAX - fi->reg_val_prev + reg_val;
Isn't it the abs_diff() reimplementation?
> + /*
> + * HW register value is accumulated count of pulses from
> + * PWM fan with the scale of 2 pulses per rotation.
> + */
> + rotations = pulses / 2;
> +
> + time = jiffies_delta_to_msecs(time_now - fi->time_prev);
> + if (unlikely(!time)) {
> + ret = -EAGAIN;
> + goto exit;
> + }
> +
> + /*
> + * Convert to minutes for calculating RPM.
> + * RPM = number of rotations * msecs per minute / time in msecs
> + */
> + *val = DIV_ROUND_UP(rotations * (MSEC_PER_SEC * 60), time);
> +
> + fi->reg_val_prev = reg_val;
> + fi->time_prev = time_now;
> +exit:
> + mutex_unlock(&hwmon->hwmon_lock);
> + intel_runtime_pm_put(ddat->uncore->rpm, wakeref);
> + return ret;
> +}
--
With Best Regards,
Andy Shevchenko
