[PATCH v2] iio: imu: bmi270: fix zero timestamp in triggered buffer

[Liu Yufei <lyf98405@gmail.com>]

The BMI270's own trigger uses iio_trigger_poll_nested() from
the threaded IRQ handler, bypassing the pollfunc top half.
This leaves the buffer timestamp at zero or a stale value.

Capture the timestamp in the hard IRQ handler for the device's
own trigger. Preserve the pollfunc timestamp for ordinary
external triggers, and use the current IIO clock when a nested
external trigger has no timestamp. Clear the pollfunc timestamp
after processing.

Testing on Orange Pi Zero 2W reproduced 256 zero timestamps
with the original own trigger and 256 repeated stale timestamps
after switching from an ordinary to a nested external trigger.
With v2, 1280 samples across the tested trigger and restart
paths had no zero or non-increasing timestamps.

Fixes: a1854d55f54b ("iio: imu: bmi270: add support for data ready interrupt trigger")
Cc: stable@vger.kernel.org
Signed-off-by: Liu Yufei <lyf98405@gmail.com>
---
Fix invalid BMI270 IIO buffer timestamps when the device's own
trigger uses iio_trigger_poll_nested(). This bypasses the
pollfunc top half, so its timestamp can remain zero or retain
an old value.

Capture the timestamp in the hard IRQ handler for the device's
own trigger. Keep pollfunc timestamps for ordinary external
triggers, and use the current IIO clock when a nested external
trigger has no timestamp. Clear the pollfunc timestamp after use.

Tested on Orange Pi Zero 2W (arm64, Linux 7.3.0), with a
physical BMI270 connected over I2C, using INT1 at 100 Hz.
The baseline produced 256/256 zero timestamps using its own
trigger, and 256/256 stale timestamps after switching an
external trigger from ordinary to nested polling.

With v2, 1,280 samples across own hardware triggering,
ordinary and nested external triggering, and stop/restart
tests had no zero, repeated, or decreasing timestamps.
External triggers were generated by a temporary test module;
sensor data was read from the physical BMI270.
---
Changes in v2:
- Capture the timestamp in the hard IRQ handler.
- Use the IRQ timestamp for the device's own trigger.
- Fall back to the current time when no pollfunc timestamp exists.
- Clear the pollfunc timestamp after processing.
- Link to v1: https://patch.msgid.link/20261028-bmi270-fix-timestamp-v1-1-99c0e5fe7d0c@gmail.com

To: Alex Lanzano <lanzano.alex@gmail.com>
To: Jonathan Cameron <jic23@kernel.org>
To: David Lechner <dlechner@baylibre.com>
To: Nuno Sá <nuno.sa@analog.com>
To: Andy Shevchenko <andy@kernel.org>
To: Gustavo Silva <gustavograzs@gmail.com>
Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Cc: linux-iio@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
---
 drivers/iio/imu/bmi270/bmi270_core.c | 21 ++++++++++++++++++++-
 1 file changed, 20 insertions(+), 1 deletion(-)

diff --git a/drivers/iio/imu/bmi270/bmi270_core.c b/drivers/iio/imu/bmi270/bmi270_core.c
index fbcf6bb87acc..6b11e91eabff 100644
--- a/drivers/iio/imu/bmi270/bmi270_core.c
+++ b/drivers/iio/imu/bmi270/bmi270_core.c
@@ -157,6 +157,7 @@ struct bmi270_data {
 	const struct bmi270_chip_info *chip_info;
 	enum bmi270_irq_pin irq_pin;
 	struct iio_trigger *trig;
+	s64 irq_timestamp;
 	 /* Protect device's private data from concurrent access */
 	struct mutex mutex;
 	bool steps_enabled;
@@ -755,6 +756,16 @@ static int bmi270_get_odr(struct bmi270_data *data, int chan_type, int *odr,
 	return -EINVAL;
 }
 
+static irqreturn_t bmi270_irq_handler(int irq, void *private)
+{
+	struct iio_dev *indio_dev = private;
+	struct bmi270_data *data = iio_priv(indio_dev);
+
+	data->irq_timestamp = iio_get_time_ns(indio_dev);
+
+	return IRQ_WAKE_THREAD;
+}
+
 static irqreturn_t bmi270_irq_thread_handler(int irq, void *private)
 {
 	struct iio_dev *indio_dev = private;
@@ -842,6 +853,13 @@ static irqreturn_t bmi270_trigger_handler(int irq, void *p)
 	struct bmi270_data *data = iio_priv(indio_dev);
 	int ret;
 
+	if (iio_trigger_using_own(indio_dev)) {
+		pf->timestamp = data->irq_timestamp;
+		data->irq_timestamp = 0;
+	} else if (!pf->timestamp) {
+		pf->timestamp = iio_get_time_ns(indio_dev);
+	}
+
 	guard(mutex)(&data->mutex);
 
 	ret = regmap_bulk_read(data->regmap, BMI270_ACCEL_X_REG,
@@ -854,6 +872,7 @@ static irqreturn_t bmi270_trigger_handler(int irq, void *p)
 	iio_push_to_buffers_with_timestamp(indio_dev, &data->buffer,
 					   pf->timestamp);
 done:
+	pf->timestamp = 0;
 	iio_trigger_notify_done(indio_dev->trig);
 	return IRQ_HANDLED;
 }
@@ -1430,7 +1449,7 @@ static int bmi270_trigger_probe(struct bmi270_data *data,
 	data->trig->ops = &bmi270_trigger_ops;
 	iio_trigger_set_drvdata(data->trig, data);
 
-	ret = devm_request_threaded_irq(data->dev, irq, NULL,
+	ret = devm_request_threaded_irq(data->dev, irq, bmi270_irq_handler,
 					bmi270_irq_thread_handler,
 					IRQF_ONESHOT, "bmi270-int", indio_dev);
 	if (ret)

---
base-commit: 09f742b49cb2728086d78be2b0b35e4d1d71fc85
change-id: 20261028-bmi270-fix-timestamp-48a194b69db1

Best regards,
--  
Liu Yufei <lyf98405@gmail.com>