Re: [PATCH v1] drm/i915/hwmon: expose fan speed

[Raag Jadav <raag.jadav@intel.com>]

On Wed, Jul 24, 2024 at 02:11:40PM +0530, Nilawar, Badal wrote:
> 
> 
> On 12-07-2024 17:53, 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
> > 
> > Signed-off-by: Raag Jadav <raag.jadav@intel.com>
> > ---
> >   drivers/gpu/drm/i915/gt/intel_gt_regs.h |  2 +
> >   drivers/gpu/drm/i915/i915_hwmon.c       | 71 +++++++++++++++++++++++++
> >   2 files changed, 73 insertions(+)
> > 
> > diff --git a/drivers/gpu/drm/i915/gt/intel_gt_regs.h b/drivers/gpu/drm/i915/gt/intel_gt_regs.h
> > index e42b3a5d4e63..407d8152755a 100644
> > --- a/drivers/gpu/drm/i915/gt/intel_gt_regs.h
> > +++ b/drivers/gpu/drm/i915/gt/intel_gt_regs.h
> > @@ -1553,6 +1553,8 @@
> >   #define VLV_RENDER_C0_COUNT			_MMIO(0x138118)
> >   #define VLV_MEDIA_C0_COUNT			_MMIO(0x13811c)
> > +#define GEN12_PWM_FAN_SPEED			_MMIO(0x138140)
> > +
> >   #define GEN12_RPSTAT1				_MMIO(0x1381b4)
> >   #define   GEN12_VOLTAGE_MASK			REG_GENMASK(10, 0)
> >   #define   GEN12_CAGF_MASK			REG_GENMASK(19, 11)
> > diff --git a/drivers/gpu/drm/i915/i915_hwmon.c b/drivers/gpu/drm/i915/i915_hwmon.c
> > index 49db3e09826c..f829c7837d83 100644
> > --- a/drivers/gpu/drm/i915/i915_hwmon.c
> > +++ b/drivers/gpu/drm/i915/i915_hwmon.c
> > @@ -36,6 +36,7 @@ struct hwm_reg {
> >   	i915_reg_t pkg_rapl_limit;
> >   	i915_reg_t energy_status_all;
> >   	i915_reg_t energy_status_tile;
> > +	i915_reg_t fan_speed;
> >   };
> >   struct hwm_energy_info {
> > @@ -43,11 +44,17 @@ struct hwm_energy_info {
> >   	long accum_energy;			/* Accumulated energy for energy1_input */
> >   };
> > +struct hwm_fan_info {
> > +	u32 reg_val_prev;
> > +	u32 time_prev;
> > +};
> > +
> >   struct hwm_drvdata {
> >   	struct i915_hwmon *hwmon;
> >   	struct intel_uncore *uncore;
> >   	struct device *hwmon_dev;
> >   	struct hwm_energy_info ei;		/*  Energy info for energy1_input */
> > +	struct hwm_fan_info fi;			/*  Fan info for fan1_input */
> >   	char name[12];
> >   	int gt_n;
> >   	bool reset_in_progress;
> > @@ -276,6 +283,7 @@ static const struct hwmon_channel_info * const hwm_info[] = {
> >   	HWMON_CHANNEL_INFO(power, HWMON_P_MAX | HWMON_P_RATED_MAX | HWMON_P_CRIT),
> >   	HWMON_CHANNEL_INFO(energy, HWMON_E_INPUT),
> >   	HWMON_CHANNEL_INFO(curr, HWMON_C_CRIT),
> > +	HWMON_CHANNEL_INFO(fan, HWMON_F_INPUT),
> >   	NULL
> >   };
> > @@ -613,6 +621,55 @@ hwm_curr_write(struct hwm_drvdata *ddat, u32 attr, long val)
> >   	}
> >   }
> > +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;
> > +	}
> > +}
> > +
> > +static int
> > +hwm_fan_read(struct hwm_drvdata *ddat, u32 attr, long *val)
> > +{
> > +	struct i915_hwmon *hwmon = ddat->hwmon;
> > +	u32 reg_val, rotation, time, time_now;
> > +	intel_wakeref_t wakeref;
> > +
> > +	switch (attr) {
> > +	case hwmon_fan_input:
> > +		with_intel_runtime_pm(ddat->uncore->rpm, wakeref)
> Do we expect fan running when device is in D3? If not then we should use
> with_intel_runtime_pm_if_active here otherwise report fan speed 0.

Yes, it can be running depending on package temperature.
So better to rely on hardware value.

Raag