[PATCH 09/15] thermal/drivers/samsung: acpm-tmu: Fix IRQ locking and error handling

[Tudor Ambarus]

acpm_tmu_has_pending_irq() acquires and releases sensor->lock around the
INTPEND read, and acpm_tmu_thread_fn() re-acquires it to call
ops->clear_tz_irq(), leaving a window where concurrent .set_trips() or
.change_mode() calls can modify sensor state in between. Moreover, if
ops->clear_tz_irq() fails, acpm_tmu_thread_fn() still sets handled = true
and updates the thermal zone while INTPEND remains asserted; conversely,
returning IRQ_NONE on a level-high IRQF_ONESHOT line re-triggers the
interrupt up to 100,000 times before the spurious IRQ detector disables
it, so unthrottled dev_err() calls flood the kernel log.

Replace acpm_tmu_has_pending_irq() with acpm_tmu_clear_pending_irq() so
both the INTPEND check and ops->clear_tz_irq() run under a single
guard(mutex)(&sensor->lock), only mark the IRQ handled and update the
thermal zone when an interrupt was pending and cleared, and rate-limit
the error messages on both IRQ_NONE failure paths in the threaded IRQ
handler.

Fixes: 50a2c5d4062a ("thermal/drivers/samsung: Add Exynos ACPM TMU driver GS101")
Signed-off-by: Tudor Ambarus <tudor.ambarus at linaro.org>
---
 drivers/thermal/samsung/acpm-tmu.c | 42 ++++++++++++++++++--------------------
 1 file changed, 20 insertions(+), 22 deletions(-)

diff --git a/drivers/thermal/samsung/acpm-tmu.c b/drivers/thermal/samsung/acpm-tmu.c
index 65be8884a8c5..42b338d8d093 100644
--- a/drivers/thermal/samsung/acpm-tmu.c
+++ b/drivers/thermal/samsung/acpm-tmu.c
@@ -330,11 +330,12 @@ static const struct thermal_zone_device_ops acpm_tmu_sensor_ops = {
 	.set_trips = acpm_tmu_set_trips,
 };
 
-static int acpm_tmu_has_pending_irq(struct acpm_tmu_sensor *sensor,
-				    bool *pending_irq)
+static bool acpm_tmu_clear_pending_irq(struct acpm_tmu_sensor *sensor)
 {
 	struct acpm_tmu_priv *priv = sensor->priv;
+	const struct acpm_tmu_ops *ops = &priv->handle->ops->tmu;
 	unsigned long mask = sensor->group->mask;
+	bool pending_irq = false;
 	int i, ret;
 	u32 val;
 
@@ -343,53 +344,50 @@ static int acpm_tmu_has_pending_irq(struct acpm_tmu_sensor *sensor,
 	for_each_set_bit(i, &mask, EXYNOS_TMU_SENSORS_MAX_COUNT) {
 		ret = regmap_field_read(priv->regmap_fields[i], &val);
 		if (ret)
-			return ret;
+			return false;
 
 		if (val) {
-			*pending_irq = true;
+			pending_irq = true;
 			break;
 		}
 	}
 
-	return 0;
+	if (!pending_irq)
+		return false;
+
+	ret = ops->clear_tz_irq(priv->handle, priv->mbox_chan_id,
+				sensor->group->id);
+	if (ret) {
+		dev_err_ratelimited(priv->dev,
+				    "Sensor %u: failed to clear IRQ (%d)\n",
+				    sensor->group->id, ret);
+		return false;
+	}
+
+	return true;
 }
 
 static irqreturn_t acpm_tmu_thread_fn(int irq, void *id)
 {
 	struct acpm_tmu_priv *priv = id;
-	struct acpm_handle *handle = priv->handle;
-	const struct acpm_tmu_ops *ops = &handle->ops->tmu;
 	struct device *dev = priv->dev;
 	bool handled = false;
 	int i, ret;
 
 	ret = pm_runtime_resume_and_get(dev);
 	if (ret) {
-		dev_err(dev, "Failed to resume: %d\n", ret);
+		dev_err_ratelimited(dev, "Failed to resume: %d\n", ret);
 		return IRQ_NONE;
 	}
 
 	for (i = 0; i < priv->num_sensors; i++) {
 		struct acpm_tmu_sensor *sensor = &priv->sensors[i];
-		bool pending_irq = false;
-
-		if (!sensor->tzd)
-			continue;
 
-		ret = acpm_tmu_has_pending_irq(sensor, &pending_irq);
-		if (ret || !pending_irq)
+		if (!sensor->tzd || !acpm_tmu_clear_pending_irq(sensor))
 			continue;
 
 		handled = true;
 
-		scoped_guard(mutex, &sensor->lock) {
-			ret = ops->clear_tz_irq(handle, priv->mbox_chan_id,
-						sensor->group->id);
-			if (ret)
-				dev_err(priv->dev, "Sensor %d: failed to clear IRQ (%d)\n",
-					i, ret);
-		}
-
 		thermal_zone_device_update(sensor->tzd,
 					   THERMAL_EVENT_UNSPECIFIED);
 	}

-- 
2.56.0.257.gf7497c7d27-goog