[PATCH v3 RESEND] thermal: qoriq: Only enable sites that actually exist

[Sebastian Krzyszkowiak]

On i.MX8MQ, enabling monitoring sites that aren't connected to anything
can cause unwanted side effects on some units. This seems to happen
once some of these sites report out-of-range readings and results in
sensor misbehavior, such as thermal zone readings getting stuck or even
suddenly reporting an impossibly high value, triggering emergency
shutdowns.

The datasheet lists all non-existent sites as "reserved" and doesn't
make any guarantees about being able to enable them at all, so let's
not do that. Instead, iterate over sensor DT nodes and only enable
monitoring sites that are specified there prior to registering their
thermal zones. This still fixes the issue with bogus data being
reported on the first reading, but doesn't introduce problems that
come with reading from non-existent sites.

Fixes: 45038e03d633 ("thermal: qoriq: Enable all sensors before registering them")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Sebastian Krzyszkowiak <sebastian.krzyszkowiak@xxxxxxx>
---
Resent <20220321170852.654094-1-sebastian.krzyszkowiak@xxxxxxx>
v3: add cc: stable
v2: augment the commit message with details on what the patch is doing
---
 drivers/thermal/qoriq_thermal.c | 63 ++++++++++++++++++++++-----------
 1 file changed, 43 insertions(+), 20 deletions(-)

diff --git a/drivers/thermal/qoriq_thermal.c b/drivers/thermal/qoriq_thermal.c
index 73049f9bea25..ef0848849ee2 100644
--- a/drivers/thermal/qoriq_thermal.c
+++ b/drivers/thermal/qoriq_thermal.c
@@ -32,7 +32,6 @@
 #define TMR_DISABLE	0x0
 #define TMR_ME		0x80000000
 #define TMR_ALPF	0x0c000000
-#define TMR_MSITE_ALL	GENMASK(15, 0)
 
 #define REGS_TMTMIR	0x008	/* Temperature measurement interval Register */
 #define TMTMIR_DEFAULT	0x0000000f
@@ -129,33 +128,51 @@ static const struct thermal_zone_of_device_ops tmu_tz_ops = {
 static int qoriq_tmu_register_tmu_zone(struct device *dev,
 				       struct qoriq_tmu_data *qdata)
 {
-	int id;
+	int ret = 0;
+	struct device_node *np, *child, *sensor_np;
 
-	if (qdata->ver == TMU_VER1) {
-		regmap_write(qdata->regmap, REGS_TMR,
-			     TMR_MSITE_ALL | TMR_ME | TMR_ALPF);
-	} else {
-		regmap_write(qdata->regmap, REGS_V2_TMSR, TMR_MSITE_ALL);
-		regmap_write(qdata->regmap, REGS_TMR, TMR_ME | TMR_ALPF_V2);
-	}
+	np = of_find_node_by_name(NULL, "thermal-zones");
+	if (!np)
+		return -ENODEV;
+
+	sensor_np = of_node_get(dev->of_node);
 
-	for (id = 0; id < SITES_MAX; id++) {
+	for_each_available_child_of_node(np, child) {
 		struct thermal_zone_device *tzd;
-		struct qoriq_sensor *sensor = &qdata->sensor[id];
-		int ret;
+		struct qoriq_sensor *sensor;
+		int id, site;
+
+		ret = thermal_zone_of_get_sensor_id(child, sensor_np, &id);
+
+		if (ret < 0) {
+			dev_err(dev, "failed to get valid sensor id: %d\n", ret);
+			of_node_put(child);
+			break;
+		}
 
+		sensor = &qdata->sensor[id];
 		sensor->id = id;
 
+		/* Enable monitoring */
+		if (qdata->ver == TMU_VER1) {
+			site = 0x1 << (15 - id);
+			regmap_update_bits(qdata->regmap, REGS_TMR,
+					   site | TMR_ME | TMR_ALPF,
+					   site | TMR_ME | TMR_ALPF);
+		} else {
+			site = 0x1 << id;
+			regmap_update_bits(qdata->regmap, REGS_V2_TMSR, site, site);
+			regmap_write(qdata->regmap, REGS_TMR, TMR_ME | TMR_ALPF_V2);
+		}
+
 		tzd = devm_thermal_zone_of_sensor_register(dev, id,
 							   sensor,
 							   &tmu_tz_ops);
-		ret = PTR_ERR_OR_ZERO(tzd);
-		if (ret) {
-			if (ret == -ENODEV)
-				continue;
-
-			regmap_write(qdata->regmap, REGS_TMR, TMR_DISABLE);
-			return ret;
+		if (IS_ERR(tzd)) {
+			ret = PTR_ERR(tzd);
+			dev_err(dev, "failed to register thermal zone: %d\n", ret);
+			of_node_put(child);
+			break;
 		}
 
 		if (devm_thermal_add_hwmon_sysfs(tzd))
@@ -164,7 +181,13 @@ static int qoriq_tmu_register_tmu_zone(struct device *dev,
 
 	}
 
-	return 0;
+	of_node_put(sensor_np);
+	of_node_put(np);
+
+	if (ret)
+		regmap_write(qdata->regmap, REGS_TMR, TMR_DISABLE);
+
+	return ret;
 }
 
 static int qoriq_tmu_calibration(struct device *dev,
-- 
2.35.1