Re: invensense mpu9250 ak8963 and devicetree

[Philippe De Muyter <phdm@macq.eu>]

Hello Jean-Baptiste,

thank you for your answer

I work actually with a nvidia-provided 4.9 kernel that I cannot change.
Up to now I have incorporated the mpu9250 related patches up to v4.12.

Do you think I should simply replace the inv_mpu6050 driver files of v4.9
by their v5.11 (or newer) counterparts ?

Thanks

Philippe

On Thu, Mar 04, 2021 at 09:12:47AM +0000, Jean-Baptiste Maneyrol wrote:
> Hello Philippe,
> 
> I would recommend letting mpu9250 chip drives the magnetometer instead of using the ak8963 driver.
> 
> This is simpler to use and guarantees a good synchronization between all sensors and no possible latency coming from kernel scheduling when polling the magnetometer. And it enables the use of spi bus for connecting the device.
> 
> You just need to define mpu9250 dts without an i2c-gate, and delete all definition of ak8963 chip.
> 
> Best regards,
> JB
> 
> 
> From: Philippe De Muyter <phdm@macq.eu>
> Sent: Wednesday, March 3, 2021 16:31
> To: linux-iio@vger.kernel.org <linux-iio@vger.kernel.org>
> Subject: invensense mpu9250 ak8963 and devicetree 
>  
> Hello,
> 
> I am trying to use a mpu9250 imu, but I have trouble with the ak8963 part.
> 
> Currently, ak8975_probe fails in this code :
> 
>         /* Fetch the regulators */
>         data->vdd = devm_regulator_get(&client->dev, "vdd");
>         if (IS_ERR(data->vdd))
>                 return PTR_ERR(data->vdd);
>         data->vid = devm_regulator_get(&client->dev, "vid");
>         if (IS_ERR(data->vid))
>                 return PTR_ERR(data->vid);
> 
> but Documentation/devicetree/bindings/iio/magnetometer/asahi-kasei,ak8975.yaml
> says :
> 
>   vdd-supply:
>     description: |
>       an optional regulator that needs to be on to provide VDD power to
>       the sensor.
> 
> I have no vdd or vdd-supply property in my ak8963 description.
> 
> Is that unrelated ?
> 
> What should I write in my dts file for this ak8963 embedded in a mpu9250 ?
> 
> Thanks in advance
> 
> Philippe
> 
> -- 
> Philippe De Muyter +32 2 6101532 Macq SA rue de l'Aeronef 2 B-1140 Bruxelles