linux-kernel - Re: [PATCH v3] drm/i915/hwmon: expose fan speed

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Message-ID: <ZrN1i2snlz8tSA1M@ashyti-mobl2.lan>
Date: Wed, 7 Aug 2024 14:24:27 +0100
From: Andi Shyti <andi.shyti@...ux.intel.com>
To: Raag Jadav <raag.jadav@...el.com>
Cc: jani.nikula@...ux.intel.com, joonas.lahtinen@...ux.intel.com,
	rodrigo.vivi@...el.com, tursulin@...ulin.net, airlied@...il.com,
	daniel@...ll.ch, linux@...ck-us.net,
	intel-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
	linux-hwmon@...r.kernel.org, linux-kernel@...r.kernel.org,
	anshuman.gupta@...el.com, badal.nilawar@...el.com,
	riana.tauro@...el.com, ashutosh.dixit@...el.com,
	karthik.poosa@...el.com, andriy.shevchenko@...ux.intel.com
Subject: Re: [PATCH v3] drm/i915/hwmon: expose fan speed

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?
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.

Are we expecting more cases here?

Andi