linux-kernel - Re: [PATCH v2] thermal/of: support thermal zones w/o trips subnode

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Message-ID: <CAGXv+5ERoH=jQGzo=mo2K-r3Meh2-5Kgvjf9Eh7bfNgcQYfWoA@mail.gmail.com>
Date: Mon, 12 Aug 2024 12:46:35 +0800
From: Chen-Yu Tsai <wenst@...omium.org>
To: Dragan Simic <dsimic@...jaro.org>
Cc: Daniel Lezcano <daniel.lezcano@...aro.org>, Amit Kucheria <amitk@...nel.org>, 
	Zhang Rui <rui.zhang@...el.com>, Icenowy Zheng <uwu@...nowy.me>, Mark Brown <broonie@...nel.org>, 
	linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-arm-kernel@...ts.infradead.org, linux-sunxi@...ts.linux.dev, 
	Nícolas F. R. A. Prado <nfraprado@...labora.com>, 
	AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>, 
	Matthias Brugger <matthias.bgg@...il.com>, linux-mediatek@...ts.infradead.org, 
	Hsin-Te Yuan <yuanhsinte@...omium.org>
Subject: Re: [PATCH v2] thermal/of: support thermal zones w/o trips subnode

On Mon, Aug 12, 2024 at 9:22 AM Dragan Simic <dsimic@...jaro.org> wrote:
>
> Hello Chen-Yu,
>
> Thanks for the patch.  Please see one comment below.
>
> On 2024-08-09 09:08, Chen-Yu Tsai wrote:
> > From: Icenowy Zheng <uwu@...nowy.me>
> >
> > Although the current device tree binding of thermal zones require the
> > trips subnode, the binding in kernel v5.15 does not require it, and
> > many
> > device trees shipped with the kernel, for example,
> > allwinner/sun50i-a64.dtsi and mediatek/mt8183-kukui.dtsi in ARM64,
> > still
> > comply to the old binding and contain no trips subnode.
> >
> > Allow the code to successfully register thermal zones w/o trips subnode
> > for DT binding compatibility now.
> >
> > Furtherly, the inconsistency between DTs and bindings should be
> > resolved
> > by either adding empty trips subnode or dropping the trips subnode
> > requirement.
> >
> > Fixes: d0c75fa2c17f ("thermal/of: Initialize trip points separately")
> > Signed-off-by: Icenowy Zheng <uwu@...nowy.me>
> > Reviewed-by: Mark Brown <broonie@...nel.org>
> > Signed-off-by: Chen-Yu Tsai <wenst@...omium.org>
> > ---
> > Resurrecting this patch specifically for MediaTek MT8183 Kukui devices.
> >
> > Changes since v1:
> > - set *ntrips at beginning of thermal_of_trips_init()
> > - Keep goto out_of_node_put in of_get_child_count(trips) == 0 branch
> > - Check return value of thermal_of_trips_init(), if it is -ENXIO, print
> >   warning and clear |trips| pointer
> > - Drop |mask| change, as the variable was removed
> >
> > I kept Mark's reviewed-by since the changes are more stylish than
> > functional.
> > ---
> >  drivers/thermal/thermal_of.c | 19 ++++++++++++-------
> >  1 file changed, 12 insertions(+), 7 deletions(-)
> >
> > diff --git a/drivers/thermal/thermal_of.c
> > b/drivers/thermal/thermal_of.c
> > index aa34b6e82e26..f237e74c92fc 100644
> > --- a/drivers/thermal/thermal_of.c
> > +++ b/drivers/thermal/thermal_of.c
> > @@ -128,16 +128,17 @@ static struct thermal_trip
> > *thermal_of_trips_init(struct device_node *np, int *n
> >       struct device_node *trips, *trip;
> >       int ret, count;
> >
> > +     *ntrips = 0;
> >       trips = of_get_child_by_name(np, "trips");
> >       if (!trips) {
> > -             pr_err("Failed to find 'trips' node\n");
> > -             return ERR_PTR(-EINVAL);
> > +             pr_debug("Failed to find 'trips' node\n");
> > +             return ERR_PTR(-ENXIO);
> >       }
> >
> >       count = of_get_child_count(trips);
> >       if (!count) {
> > -             pr_err("No trip point defined\n");
> > -             ret = -EINVAL;
> > +             pr_debug("No trip point defined\n");
> > +             ret = -ENXIO;
> >               goto out_of_node_put;
> >       }
> >
> > @@ -162,7 +163,6 @@ static struct thermal_trip
> > *thermal_of_trips_init(struct device_node *np, int *n
> >
> >  out_kfree:
> >       kfree(tt);
> > -     *ntrips = 0;
> >  out_of_node_put:
> >       of_node_put(trips);
>
> It might be a bit cleaner to keep the "*ntrips = 0" assignment
> in the error handling path(s) only, with the positions of the goto
> labels adjusted a bit, and then assign -ENXIO to "ret" and jump
> to the right label when of_get_child_by_name(np, "trips") fails,
> instead of returning from there.
>
> If it's unclear what I'm talking about, please let me know and
> I'll send back the proposed hunk.

I think I understand: move "*ntrips = 0" to after of_node_put() in the
error path, and have the "!trips" branch jump to "out_of_node_put" as
well. That works since of_node_put() checks the pointer first.

I'll wait a bit and see if there are any more comments.

ChenYu

> > @@ -490,8 +490,13 @@ static struct thermal_zone_device
> > *thermal_of_zone_register(struct device_node *
> >
> >       trips = thermal_of_trips_init(np, &ntrips);
> >       if (IS_ERR(trips)) {
> > -             pr_err("Failed to find trip points for %pOFn id=%d\n", sensor, id);
> > -             return ERR_CAST(trips);
> > +             if (PTR_ERR(trips) != -ENXIO) {
> > +                     pr_err("Failed to find trip points for %pOFn id=%d\n", sensor, id);
> > +                     return ERR_CAST(trips);
> > +             }
> > +
> > +             pr_warn("Failed to find trip points for %pOFn id=%d\n", sensor, id);
> > +             trips = NULL;
> >       }
> >
> >       ret = thermal_of_monitor_init(np, &delay, &pdelay);