linux-kernel - Re: [PATCH v1] thermal/of: Fix cdev lookup in thermal_of_should

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Message-ID: <CAKchOA1gfsE+URhBZCwbNrMmX8Xw+a4LR4DHuv5o+-6-mUd30w@mail.gmail.com>
Date: Sat, 22 Feb 2025 07:27:36 +0800
From: Yu-Che Cheng <giver@...omium.org>
To: "Rafael J. Wysocki" <rjw@...ysocki.net>
Cc: Linux PM <linux-pm@...r.kernel.org>, LKML <linux-kernel@...r.kernel.org>, 
	Lukasz Luba <lukasz.luba@....com>, Daniel Lezcano <daniel.lezcano@...aro.org>, 
	Yu-Che Cheng <giver@...omium.org>
Subject: Re: [PATCH v1] thermal/of: Fix cdev lookup in thermal_of_should_bind()

Reviewed-by: Yu-Che Cheng <giver@...omium.org>
Tested-by: Yu-Che Cheng <giver@...omium.org>

On Sat, Feb 22, 2025 at 12:57 AM Rafael J. Wysocki <rjw@...ysocki.net> wrote:
>
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
>
> Since thermal_of_should_bind() terminates the loop after processing
> the first child found in cooling-maps, it will never match more than
> one cdev to a given trip point which is incorrect, as there may be
> cooling-maps associating one trip point with multiple cooling devices.
>
> Address this by letting the loop continue until either all
> children have been processed or a matching one has been found.
>
> To avoid adding conditionals or goto statements, put the loop in
> question into a separate function and make that function return
> right away after finding a matching cooling-maps entry.
>
> Fixes: 94c6110b0b13 ("thermal/of: Use the .should_bind() thermal zone callback")
> Link: https://lore.kernel.org/linux-pm/20250219-fix-thermal-of-v1-1-de36e7a590c4@chromium.org/
> Reported-by: Yu-Che Cheng <giver@...omium.org>
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> ---
>  drivers/thermal/thermal_of.c |   50 ++++++++++++++++++++++++-------------------
>  1 file changed, 29 insertions(+), 21 deletions(-)
>
> --- a/drivers/thermal/thermal_of.c
> +++ b/drivers/thermal/thermal_of.c
> @@ -274,6 +274,34 @@
>         return true;
>  }
>
> +static bool thermal_of_cm_lookup(struct device_node *cm_np,
> +                                const struct thermal_trip *trip,
> +                                struct thermal_cooling_device *cdev,
> +                                struct cooling_spec *c)
> +{
> +       for_each_child_of_node_scoped(cm_np, child) {
> +               struct device_node *tr_np;
> +               int count, i;
> +
> +               tr_np = of_parse_phandle(child, "trip", 0);
> +               if (tr_np != trip->priv)
> +                       continue;
> +
> +               /* The trip has been found, look up the cdev. */
> +               count = of_count_phandle_with_args(child, "cooling-device",
> +                                                  "#cooling-cells");
> +               if (count <= 0)
> +                       pr_err("Add a cooling_device property with at least one device\n");
> +
> +               for (i = 0; i < count; i++) {
> +                       if (thermal_of_get_cooling_spec(child, i, cdev, c))
> +                               return true;
> +               }
> +       }
> +
> +       return false;
> +}
> +
>  static bool thermal_of_should_bind(struct thermal_zone_device *tz,
>                                    const struct thermal_trip *trip,
>                                    struct thermal_cooling_device *cdev,
> @@ -293,27 +321,7 @@
>                 goto out;
>
>         /* Look up the trip and the cdev in the cooling maps. */
> -       for_each_child_of_node_scoped(cm_np, child) {
> -               struct device_node *tr_np;
> -               int count, i;
> -
> -               tr_np = of_parse_phandle(child, "trip", 0);
> -               if (tr_np != trip->priv)
> -                       continue;
> -
> -               /* The trip has been found, look up the cdev. */
> -               count = of_count_phandle_with_args(child, "cooling-device", "#cooling-cells");
> -               if (count <= 0)
> -                       pr_err("Add a cooling_device property with at least one device\n");
> -
> -               for (i = 0; i < count; i++) {
> -                       result = thermal_of_get_cooling_spec(child, i, cdev, c);
> -                       if (result)
> -                               break;
> -               }
> -
> -               break;
> -       }
> +       result = thermal_of_cm_lookup(cm_np, trip, cdev, c);
>
>         of_node_put(cm_np);
>  out:
>
>
>