[v4] thermal/of: support thermal zones w/o trips subnode

From: Icenowy Zheng <uwu@icenowy.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@icenowy.me>
[wenst@chromium.org: Reworked logic and kernel log messages]
Signed-off-by: Chen-Yu Tsai <wenst@chromium.org>
---
This patch is based on Krzysztof's cleanup patches
  - thermal: of: Use scoped memory and OF handling to simplify thermal_of_trips_init() [1]

Changes since v3:
  - Set *ntrips = 0 and return NULL from thermal_of_trips_init() if
    no trip points are found in the device tree (Rafael)
  - Dropped log level of "no trip points found" message to INFO
  - Reworded new "failed to find trip points" message to "no trip points
    found"
  - Reworded existing "failed to find trip points" message to "failed to
    parse trip points"

I dropped Mark's reviewed-by because of the new changes.

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

---
 drivers/thermal/thermal_of.c | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

On 28/10/2024 18:19, Daniel Lezcano wrote:
> From: Icenowy Zheng <uwu@icenowy.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@icenowy.me>
> [wenst@chromium.org: Reworked logic and kernel log messages]
> Signed-off-by: Chen-Yu Tsai <wenst@chromium.org>
> Reviewed-by: Rafael J. Wysocki <rafael@kernel.org>
> Link: https://lore.kernel.org/r/20241018073139.1268995-1-wenst@chromium.org
> Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>

In order to fix a conflict when merging this patch I did the following 
changes. Let me know if you [dis]agree with the changes

This change will go through the 'fixes' branch, so for v6.12

Thanks

> ---
>   drivers/thermal/thermal_of.c | 21 ++++++++++-----------
>   1 file changed, 10 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/thermal/thermal_of.c b/drivers/thermal/thermal_of.c
> index a4caf7899f8e..07e09897165f 100644
> --- a/drivers/thermal/thermal_of.c
> +++ b/drivers/thermal/thermal_of.c
> @@ -99,18 +99,15 @@ static struct thermal_trip *thermal_of_trips_init(struct device_node *np, int *n
>   	struct device_node *trips;
>   	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);
> -	}
> +	if (!trips)
> +		return NULL;
>   
>   	count = of_get_child_count(trips);
> -	if (!count) {
> -		pr_err("No trip point defined\n");
> -		ret = -EINVAL;
> -		goto out_of_node_put;
> -	}
> +	if (!count)
> +		return NULL;
>   
>   	tt = kzalloc(sizeof(*tt) * count, GFP_KERNEL);
>   	if (!tt) {
> @@ -133,7 +130,6 @@ 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);
>   
> @@ -401,11 +397,14 @@ 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);
> +		pr_err("Failed to parse trip points for %pOFn id=%d\n", sensor, id);
>   		ret = PTR_ERR(trips);
>   		goto out_of_node_put;
>   	}
>   
> +	if (!trips)
> +		pr_info("No trip points found for %pOFn id=%d\n", sensor, id);
> +
>   	ret = thermal_of_monitor_init(np, &delay, &pdelay);
>   	if (ret) {
>   		pr_err("Failed to initialize monitoring delays from %pOFn\n", np);