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iio: imu: inv_mpu6050: Use as standalone trigger

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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.

Not suitable for backporting to stable.  It is an odd corner case
and does not represent a regression.

Fixes: 09a642b785 ("Invensense MPU6050 Device Driver.")
Cc: Jean-Baptiste Maneyrol <jmaneyrol@invensense.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Jean-Baptiste Maneyrol <jmaneyrol@invensense.com>
Link: https://lore.kernel.org/r/20210322132408.1003443-1-linus.walleij@linaro.org
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
This commit is contained in:
Linus Walleij 2021-03-22 14:24:08 +01:00 committed by Jonathan Cameron
parent 4e102429f3
commit 454c219f5d
1 changed files with 10 additions and 0 deletions
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10
drivers/iio/imu/inv_mpu6050/inv_mpu_trigger.c
View file

@ -11,6 +11,16 @@ 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;
return INV_MPU6050_SENSOR_TEMP;
}
st->chip_config.gyro_fifo_enable =
test_bit(INV_MPU6050_SCAN_GYRO_X,
indio_dev->active_scan_mask) ||