linux-kernel - Re: [PATCH v3] thermal/of: support thermal zones w/o trips subnode

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Message-ID: <CAJZ5v0hZUzubeLt2OBcG=F5QKFh-0V8yqYRoQL0iHK+y+zeZFg@mail.gmail.com>
Date: Thu, 17 Oct 2024 12:56:47 +0200
From: "Rafael J. Wysocki" <rafael@...nel.org>
To: Chen-Yu Tsai <wenst@...omium.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 v3] thermal/of: support thermal zones w/o trips subnode

On Thu, Oct 17, 2024 at 11:05 AM Chen-Yu Tsai <wenst@...omium.org> 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>
> ---
> Changes since v2:
> - Stacked on top of Krzysztof's cleanup patches
>   - thermal: of: Use scoped memory and OF handling to simplify thermal_of_trips_init() [1]
> - Adjusted to account for eliminated error path
>
> [1] https://lore.kernel.org/all/20241010-b4-cleanup-h-of-node-put-thermal-v4-2-bfbe29ad81f4@linaro.org/
>
> 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 | 20 +++++++++++++-------
>  1 file changed, 13 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/thermal/thermal_of.c b/drivers/thermal/thermal_of.c
> index 93f7c6f8d06d..be1fa6478c21 100644
> --- a/drivers/thermal/thermal_of.c
> +++ b/drivers/thermal/thermal_of.c
> @@ -99,14 +99,14 @@ static struct thermal_trip *thermal_of_trips_init(struct device_node *np, int *n
>
>         struct device_node *trips __free(device_node) = 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);

Why not

*ntrips = 0;
return NULL;

>         }
>
>         count = of_get_child_count(trips);
>         if (!count) {
> -               pr_err("No trip point defined\n");
> -               return ERR_PTR(-EINVAL);
> +               pr_debug("No trip point defined\n");
> +               return ERR_PTR(-ENXIO);

Is this based on the current mainline code?

>         }
>
>         struct thermal_trip *tt __free(kfree) = kzalloc(sizeof(*tt) * count, GFP_KERNEL);
> @@ -386,9 +386,15 @@ 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);
> -               ret = PTR_ERR(trips);
> -               goto out_of_node_put;
> +               if (PTR_ERR(trips) != -ENXIO) {
> +                       pr_err("Failed to find trip points for %pOFn id=%d\n", sensor, id);
> +                       ret = PTR_ERR(trips);
> +                       goto out_of_node_put;
> +               }
> +
> +               pr_warn("Failed to find trip points for %pOFn id=%d\n", sensor, id);

Wouldn't pr_info() be sufficient for this?

> +               trips = NULL;
> +               ntrips = 0;
>         }
>
>         ret = thermal_of_monitor_init(np, &delay, &pdelay);
> --