[PATCH v1] drm/i915/hwmon: expose package temperature

[Raag Jadav]

On Wed, Aug 28, 2024 at 04:59:00PM +0300, Andy Shevchenko wrote:
> On Wed, Aug 28, 2024 at 10:15:12AM +0530, Raag Jadav wrote:
> > Add hwmon support for temp1_input attribute, which will expose package
> > temperature in millidegree Celsius. With this in place we can monitor
> > package temperature using lm-sensors tool.
> > 
> > $ sensors
> > i915-pci-0300
> > Adapter: PCI adapter
> > in0:         990.00 mV
> > fan1:        1260 RPM
> > temp1:        +45.0°C
> > power1:           N/A  (max =  35.00 W)
> > energy1:      12.62 kJ
> 
> ...
> 
> > +static umode_t
> > +hwm_temp_is_visible(const struct hwm_drvdata *ddat, u32 attr)
> > +{
> > +	struct i915_hwmon *hwmon = ddat->hwmon;
> > +
> > +	if (attr == hwmon_temp_input && i915_mmio_reg_valid(hwmon->rg.pkg_temp))
> > +		return 0444;
> > +
> > +	return 0;
> 
> Just a question (I'm fine with this implementation): is the style in this file
> to check for correct cases first and return an err/etc at the end?

The convention is to use switch case with err being the default, so I'd say yes.

> > +}
> > +
> > +static int
> > +hwm_temp_read(struct hwm_drvdata *ddat, u32 attr, long *val)
> > +{
> > +	struct i915_hwmon *hwmon = ddat->hwmon;
> > +	intel_wakeref_t wakeref;
> > +	u32 reg_val;
> > +
> > +	if (attr == hwmon_temp_input) {
> > +		with_intel_runtime_pm(ddat->uncore->rpm, wakeref)
> > +			reg_val = intel_uncore_read(ddat->uncore, hwmon->rg.pkg_temp);
> > +
> > +		/* HW register value is in degrees, convert to millidegrees. */
> > +		*val = REG_FIELD_GET(TEMP_MASK, reg_val) * MILLIDEGREE_PER_DEGREE;
> > +		return 0;
> > +	}
> 
> ...because here we may drop an indentation level by doing it opposite
> 
> 	if (x != y)
> 		return -E...;
> 

True, but the idea is to allow more cases in the future with minimal changes.

Raag