[PATCH v2] iio: imu: inv_mpu6050: fix FIFO parsing when empty

[PATCH v2] iio: imu: inv_mpu6050: fix FIFO parsing when empty

[inv.git-commit]

From: Jean-Baptiste Maneyrol <jean-baptiste.maneyrol@tdk.com>

Now that we are reading the full FIFO in the interrupt handler,
it is possible to have an emply FIFO since we are still receiving
1 interrupt per data. Handle correctly this case instead of having
an error causing a reset of the FIFO.

Fixes: 0829edc43e0a ("iio: imu: inv_mpu6050: read the full fifo when processing data")
Cc: stable@vger.kernel.org
Signed-off-by: Jean-Baptiste Maneyrol <jean-baptiste.maneyrol@tdk.com>
---
V2: add missing stable tag

 drivers/iio/imu/inv_mpu6050/inv_mpu_ring.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/iio/imu/inv_mpu6050/inv_mpu_ring.c b/drivers/iio/imu/inv_mpu6050/inv_mpu_ring.c
index 66d4ba088e70..d4f9b5d8d28d 100644
--- a/drivers/iio/imu/inv_mpu6050/inv_mpu_ring.c
+++ b/drivers/iio/imu/inv_mpu6050/inv_mpu_ring.c
@@ -109,6 +109,8 @@ irqreturn_t inv_mpu6050_read_fifo(int irq, void *p)
 	/* compute and process only all complete datum */
 	nb = fifo_count / bytes_per_datum;
 	fifo_count = nb * bytes_per_datum;
+	if (nb == 0)
+		goto end_session;
 	/* Each FIFO data contains all sensors, so same number for FIFO and sensor data */
 	fifo_period = NSEC_PER_SEC / INV_MPU6050_DIVIDER_TO_FIFO_RATE(st->chip_config.divider);
 	inv_sensors_timestamp_interrupt(&st->timestamp, fifo_period, nb, nb, pf->timestamp);
--
2.34.1

Re: [PATCH v2] iio: imu: inv_mpu6050: fix FIFO parsing when empty

[Jonathan Cameron]

On Mon, 19 Feb 2024 15:48:25 +0000
inv.git-commit@tdk.com wrote:

> From: Jean-Baptiste Maneyrol <jean-baptiste.maneyrol@tdk.com>
> 
> Now that we are reading the full FIFO in the interrupt handler,
> it is possible to have an emply FIFO since we are still receiving
> 1 interrupt per data. Handle correctly this case instead of having
> an error causing a reset of the FIFO.
> 
> Fixes: 0829edc43e0a ("iio: imu: inv_mpu6050: read the full fifo when processing data")
> Cc: stable@vger.kernel.org
> Signed-off-by: Jean-Baptiste Maneyrol <jean-baptiste.maneyrol@tdk.com>

Would have been nice to call out that the error comes from a zero length
read (I think!).

Anyhow, applied to the fixes-togreg branch of iio.git.

I might pull this into my queue for the next merge window as we are getting close
to the end of the cycle.

Jonathan

> ---
> V2: add missing stable tag
> 
>  drivers/iio/imu/inv_mpu6050/inv_mpu_ring.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/iio/imu/inv_mpu6050/inv_mpu_ring.c b/drivers/iio/imu/inv_mpu6050/inv_mpu_ring.c
> index 66d4ba088e70..d4f9b5d8d28d 100644
> --- a/drivers/iio/imu/inv_mpu6050/inv_mpu_ring.c
> +++ b/drivers/iio/imu/inv_mpu6050/inv_mpu_ring.c
> @@ -109,6 +109,8 @@ irqreturn_t inv_mpu6050_read_fifo(int irq, void *p)
>  	/* compute and process only all complete datum */
>  	nb = fifo_count / bytes_per_datum;
>  	fifo_count = nb * bytes_per_datum;
> +	if (nb == 0)
> +		goto end_session;
>  	/* Each FIFO data contains all sensors, so same number for FIFO and sensor data */
>  	fifo_period = NSEC_PER_SEC / INV_MPU6050_DIVIDER_TO_FIFO_RATE(st->chip_config.divider);
>  	inv_sensors_timestamp_interrupt(&st->timestamp, fifo_period, nb, nb, pf->timestamp);
> --
> 2.34.1
>