[PATCH v3] drm/i915/hwmon: expose fan speed

[Raag Jadav]

On Wed, Aug 07, 2024 at 02:24:27PM +0100, Andi Shyti wrote:
> Hi Raag,
> 
> > +static umode_t
> > +hwm_fan_is_visible(const struct hwm_drvdata *ddat, u32 attr)
> > +{
> > +	struct i915_hwmon *hwmon = ddat->hwmon;
> > +
> > +	switch (attr) {
> > +	case hwmon_fan_input:
> > +		return i915_mmio_reg_valid(hwmon->rg.fan_speed) ? 0444 : 0;
> > +	default:
> > +		return 0;
> > +	}
> 
> Why do we need switch case here?

Just following the file conventions.

> Why can't this function become a single "return " line?
> 
> > +}
> > +
> > +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;
> > +	u32 reg_val, pulses, time, time_now;
> > +	intel_wakeref_t wakeref;
> > +	long rotations;
> > +	int ret = 0;
> > +
> > +	switch (attr) {
> > +	case hwmon_fan_input:
> > +		with_intel_runtime_pm(ddat->uncore->rpm, wakeref) {
> > +			mutex_lock(&hwmon->hwmon_lock);
> > +
> > +			reg_val = intel_uncore_read(ddat->uncore, hwmon->rg.fan_speed);
> > +			time_now = jiffies_to_msecs(jiffies);
> > +
> > +			/* Handle 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;
> > +
> > +			/*
> > +			 * HW register value is accumulated count of pulses from
> > +			 * PWM fan with the scale of 2 pulses per rotation.
> > +			 */
> > +			rotations = pulses >> 1;
> > +			time = time_now - fi->time_prev;
> > +
> > +			if (unlikely(!time)) {
> > +				ret = -EAGAIN;
> > +				mutex_unlock(&hwmon->hwmon_lock);
> > +				break;
> > +			}
> > +
> > +			/* Convert to minutes for calculating RPM */
> > +			*val = DIV_ROUND_UP(rotations * (60 * MSEC_PER_SEC), time);
> > +
> > +			fi->reg_val_prev = reg_val;
> > +			fi->time_prev = time_now;
> > +
> > +			mutex_unlock(&hwmon->hwmon_lock);
> > +		}
> > +		return ret;
> > +	default:
> > +		return -EOPNOTSUPP;
> > +	}
> 
> same here, can we make this function:
> 
> if (attr != hwmon_fan_input)
> 	return -EOPNOTSUPP;
> 
> and then save all the indentation.

Makes sense for hwm_fan_read(). Let me try this.

> Are we expecting more cases here?

Not for now.

Raag