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

[Chen-Yu Tsai]

From: Icenowy Zheng <uwu at 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 at icenowy.me>
[wenst at chromium.org: Reworked logic and kernel log messages]
Signed-off-by: Chen-Yu Tsai <wenst at 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(-)

diff --git a/drivers/thermal/thermal_of.c b/drivers/thermal/thermal_of.c
index 93f7c6f8d06d..abafce22c91f 100644
--- a/drivers/thermal/thermal_of.c
+++ b/drivers/thermal/thermal_of.c
@@ -99,14 +99,16 @@ 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");
+		*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");
+		*ntrips = 0;
+		return NULL;
 	}
 
 	struct thermal_trip *tt __free(kfree) = kzalloc(sizeof(*tt) * count, GFP_KERNEL);
@@ -386,11 +388,14 @@ 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);
-- 
2.47.0.rc1.288.g06298d1525-goog