Re: invensense mpu9250 ak8963 and devicetree

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

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

commit 7f25dfa01aafe3d3ac1983a0d0f895775a80c005
Author: Laxman Dewangan <ldewangan@nvidia.com>
Date:   Tue Aug 11 18:28:53 2015 +0530

    regulator: core: do not allow dummy regulator if config not selected

    Do not allow dummy regulator if DUMMY REGULATOR not selected from
    config.

    Bug 200223300

    Change-Id: I672fb4f9d70f05bf3044b63c904be54e19c8ab36
    Signed-off-by: Laxman Dewangan <ldewangan@nvidia.com>
    Reviewed-on: http://git-master/r/781784
    (cherry picked from commit 4e11e2b997d315587956e8537064277c5687bf70)
    Reviewed-on: http://git-master/r/1195179
    Signed-off-by: Venkat Reddy Talla <vreddytalla@nvidia.com>
    Reviewed-on: https://git-master.nvidia.com/r/1550248
    Tested-by: Ujwal Patel <ujwalp@nvidia.com>
    Reviewed-by: svc-mobile-coverity <svc-mobile-coverity@nvidia.com>
    Reviewed-by: svccoveritychecker <svccoveritychecker@nvidia.com>
    Reviewed-by: Shardar Mohammed <smohammed@nvidia.com>
    Tested-by: Shardar Mohammed <smohammed@nvidia.com>
    GVS: Gerrit_Virtual_Submit

And CONFIG_REGULATOR_DUMMY is disabled in the default kernel configuration
provided by nvidia :(

Philippe