Re: [PATCH v3 4/7] thermal/drivers/tegra: Add driver for Tegra30 thermal sensor

Viresh Kumar
2021-06-15T10:26:40Z

On 15-06-21, 12:03, Daniel Lezcano wrote:
>
> [Cc Viresh]
>
> On 29/05/2021 19:09, Dmitry Osipenko wrote:
> > All NVIDIA Tegra30 SoCs have a two-channel on-chip sensor unit which
> > monitors temperature and voltage of the SoC. Sensors control CPU frequency
> > throttling, which is activated by hardware once preprogrammed temperature
> > level is breached, they also send signal to Power Management controller to
> > perform emergency shutdown on a critical overheat of the SoC die. Add
> > driver for the Tegra30 TSENSOR module, exposing it as a thermal sensor
> > and a cooling device.
>
> IMO it does not make sense to expose the hardware throttling mechanism
> as a cooling device because it is not usable anywhere from the thermal
> framework.
>
> Moreover, that will collide with the thermal / cpufreq framework
> mitigation (hardware sets the frequency but the software thinks the freq
> is different), right ?

I am not even sure what the cooling device is doing here:

tegra_tsensor_set_cur_state() is not implemented and it says hardware
changed it by itself. What is the benefit you are getting out of the
cooling device here ?

> The hardware limiter should let know the cpufreq framework about the
> frequency change.
>
> https://lkml.org/lkml/2021/6/8/1792
>
> May be post the sensor without the hw limiter for now and address that
> in a separate series ?

--
viresh