Re: invensense mpu9250 ak8963 and devicetree

[Lars-Peter Clausen <lars@metafoo.de>]

On 3/9/21 11:11 AM, Philippe De Muyter wrote:
> Hello Jonathan,
> 
> Thank you for your answer that led me to the explanation.
> 
> On Mon, Mar 08, 2021 at 05:24:27PM +0000, Jonathan Cameron wrote:
>>
>> That's odd because you should get a stub regulator... For simple cases
>> where the regulator is always on, there is no need to specify a regulator,
>> you can just rely on the regulator framework giving you one that basically
>> does nothing.
>>
>> Could you have a look at why you aren't getting a dummy_regulator from the code
>> just below here?
>>
>> https://elixir.bootlin.com/linux/latest/source/drivers/regulator/core.c#L1948
>>
> 
> I use a kernel provided by nvidia that is called tegra-l4t-r32.3.1, but
> is based on v4.9.
> 
> Although the patch that provides automatically stub regulators
>   4ddfebd3b "regulator: core: Provide a dummy regulator with full constraints"
> is older than v3.13, I have found in the commits of my kernel on top of
> v4.9, this one
[...]
> And CONFIG_REGULATOR_DUMMY is disabled in the default kernel configuration
> provided by nvidia :(

To work around this you can add a fixed-regulator to your devicetree and 
connect it to the IMU. 
Seehttps://www.kernel.org/doc/Documentation/devicetree/bindings/regulator/fixed-regulator.txt

- Lars