linux-kernel - Re: [PATCH 1/3] thermal/drivers/intel: Use generic trip points for quark

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Date:   Tue, 31 Jan 2023 20:11:05 +0100
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Daniel Lezcano <daniel.lezcano@...aro.org>
Cc:     "Rafael J. Wysocki" <rafael@...nel.org>,
        srinivas.pandruvada@...ux.intel.com, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org, rui.zhang@...el.com,
        Amit Kucheria <amitk@...nel.org>
Subject: Re: [PATCH 1/3] thermal/drivers/intel: Use generic trip points for quark_dts

On Tue, Jan 31, 2023 at 5:41 PM Daniel Lezcano
<daniel.lezcano@...aro.org> wrote:
>
> On 26/01/2023 15:15, Rafael J. Wysocki wrote:
> > On Wed, Jan 18, 2023 at 7:16 PM Daniel Lezcano
> > <daniel.lezcano@...aro.org> 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.
> >>
> >> Signed-off-by: Daniel Lezcano <daniel.lezcano@...aro.org>
> >> ---
>
> [ ... ]
>
> >> -       aux_entry->tzone = thermal_zone_device_register("quark_dts",
> >> -                       QRK_MAX_DTS_TRIPS,
> >> -                       wr_mask,
> >> -                       aux_entry, &tzone_ops, NULL, 0, polling_delay);
> >> +       err = get_trip_temp(QRK_DTS_ID_TP_CRITICAL, &temperature);
> >> +       if (err)
> >> +               goto err_ret;
> >> +
> >> +       aux_entry->trips[QRK_DTS_ID_TP_CRITICAL].temperature = temperature;
> >> +       aux_entry->trips[QRK_DTS_ID_TP_CRITICAL].type = THERMAL_TRIP_CRITICAL;
> >> +
> >> +       err = get_trip_temp(QRK_DTS_ID_TP_HOT, &temperature);
> >> +       if (err)
> >> +               goto err_ret;
> >
> > If I'm not mistaken, this won't even try to register the thermal zone
> > if at least one trip cannot be initialized, but previously it was
> > registered in that case, but the trips that failed to respond were
> > disabled.
> >
> > This is a change in behavior that would at least need to be documented
> > in the changelog, but it isn't.
> >
> > I'm not sure if it is safe to make even, however.
>
> Thanks for catching this.
>
> Two solutions:
>
> 1. Set the temperature to THERMAL_TEMP_INVALID and change
> get_thermal_trip() to return -EINVAL or -ERANGE if the temperature is
> THERMAL_TEMP_INVALID
>
> 2. Register only the valid trip points.
>
> What would be the preferable way ?

I think that the trip points that are registered currently need to
still be registered after the change.

Does registering a trip point with the temperature set to
THERMAL_TEMP_INVALID cause it to be effectively disabled?