On Fri, Mar 19, 2021 at 3:35 PM Linus Walleij <linus.walleij@xxxxxxxxxx> wrote:
>
> It may happen that the MPU6050 is the only hardware
> trigger available on your system such as this:
>
> > lsiio
> Device 003: hscdtd008a
> Device 001: mpu6050
> Device 002: gp2ap002
> Device 000: ab8500-gpadc
> Trigger 000: mpu6050-dev1
>
> And when you want to use it to read periodically from
> your magnetometer like this:
>
> > iio_generic_buffer -a -c 100 -n hscdtd008a -t mpu6050-dev1
>
> Then the following happens:
>
> [ 209.951334] Internal error: Oops: 5 [#1] SMP ARM
> (...)
> [ 209.981969] Hardware name: ST-Ericsson Ux5x0 platform (Device Tree Support)
> [ 209.988925] PC is at inv_scan_query_mpu6050+0x8/0xb8
> [ 209.993914] LR is at inv_mpu6050_set_enable+0x40/0x194
>
> This is because since we are not using any channels from the
> same device, the indio_dev->active_scan_mask is NULL.
>
> Just checking for that and bailing out is however not enough:
> we have to enable some kind of FIFO for the readout to work.
> So enable the temperature as a dummy FIFO and all works
> fine.
Fixes tag?
> Cc: Jean-Baptiste Maneyrol <jmaneyrol@xxxxxxxxxxxxxx>
> Signed-off-by: Linus Walleij <linus.walleij@xxxxxxxxxx>
> ---
> drivers/iio/imu/inv_mpu6050/inv_mpu_trigger.c | 11 +++++++++++
> 1 file changed, 11 insertions(+)
>
> diff --git a/drivers/iio/imu/inv_mpu6050/inv_mpu_trigger.c b/drivers/iio/imu/inv_mpu6050/inv_mpu_trigger.c
> index f7b5a70be30f..6946d50b874a 100644
> --- a/drivers/iio/imu/inv_mpu6050/inv_mpu_trigger.c
> +++ b/drivers/iio/imu/inv_mpu6050/inv_mpu_trigger.c
> @@ -11,6 +11,17 @@ static unsigned int inv_scan_query_mpu6050(struct iio_dev *indio_dev)
> struct inv_mpu6050_state *st = iio_priv(indio_dev);
> unsigned int mask;
>
> + /*
> + * If the MPU6050 is just used as a trigger, then the scan mask
> + * is not allocated so we simply enable the temperature channel
> + * as a dummy and bail out.
> + */
> + if (!indio_dev->active_scan_mask) {
> + st->chip_config.temp_fifo_enable = true;
> + mask = INV_MPU6050_SENSOR_TEMP;
> + return mask;
A nit-pick:
return INV...;
> + }
> +
> st->chip_config.gyro_fifo_enable =
> test_bit(INV_MPU6050_SCAN_GYRO_X,
> indio_dev->active_scan_mask) ||
> --
> 2.29.2
>
--
With Best Regards,
Andy Shevchenko
