linux-kernel - Re: [PATCH 2/3] thermal/drivers/intel: Use generic trip points for processor_thermal_device

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Date:   Mon, 23 Jan 2023 11:31:54 -0800
From:   srinivas pandruvada <srinivas.pandruvada@...ux.intel.com>
To:     Daniel Lezcano <daniel.lezcano@...aro.org>, rafael@...nel.org
Cc:     linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
        rui.zhang@...el.com, Amit Kucheria <amitk@...nel.org>,
        Sumeet Pawnikar <sumeet.r.pawnikar@...el.com>,
        Shang XiaoJing <shangxiaojing@...wei.com>
Subject: Re: [PATCH 2/3] thermal/drivers/intel: Use generic trip points for
 processor_thermal_device_pci

Hi Daniel,

On Mon, 2023-01-23 at 19:02 +0100, Daniel Lezcano wrote:
> 
> Hi Srinivas,
> 
> 
> On 18/01/2023 20:09, srinivas pandruvada wrote:
> > On Wed, 2023-01-18 at 19:16 +0100, Daniel Lezcano wrote:
> > > The thermal framework gives the possibility to register the trip
> > > points with the thermal zone. When that is done, no get_trip_*
> > > ops
> > > are
> > > needed and they can be removed.
> > > 
> > > Convert ops content logic into generic trip points and register
> > > them
> > > with the
> > > thermal zone.
> > > 
> > In this scheme is the assumption is that trip point temperature
> > never
> > changes? If firmware updated the trip temperature, what needs to be
> > done?
> 
> I'm a bit confused about the situation where the firmware can change
> the 
> trip point in the back of the OSPM.
> 
> Does the firmware send a notification about the trip change? Or does
> it 
> assume the OSPM will be reading the trip point while
> monitoring/polling 
> the thermal zone ?
Firmware sends an ACPI notification. For example INT3403.

https://elixir.bootlin.com/linux/latest/C/ident/INT3403_PERF_TRIP_POINT_CHANGED


> 
> Is the question for this particular driver?
This PCH driver trips are not changed by firmware hence we don't have
to worry about here.

Thanks,
Srinivas

> 
> If the trip point is changed by the userspace (via sysfs), 
> thermal_zone_set_trip() is used which in turn changes the thermal
> trip 
> temperature directly in the generic structure and then calls the back
> set_trip_temp.
>