Re: [PATCH v4 0/6] Add support for the LTM8054 voltage regulator

[Romain Gantois]

On Sunday, 7 December 2025 19:48:18 CET Jonathan Cameron wrote:

> On Tue, 25 Nov 2025 08:37:20 -0800

>

> Guenter Roeck <linux@xxxxxxxxxxxx> wrote:

> > On 11/25/25 02:25, H. Nikolaus Schaller wrote:

> > ...

> >

> > > Another suggestion: what extending the "regulator-fixed",

> > > "regulator-gpio",

> > > "regulator-fixed-clock" pattern by some

> > > "regulator-gpio-iio-dac-current-limiter" driver to make it independent

> > > of your specific chip?

> >

> > The name is terrible ;-), but that is what I would have suggested as well.

> > I don't see anything chip specific in this code. If there is a need for

> > a regulator driver which uses gpio to enable it and a DAC for current

> > limiting, it should be made generic.

>

> Agreed - something generic is the ideal way to go.

>

> However, before going too far it is worth exploring what are common circuits

> with these things to identify what parameters we need to describe how the

> DAC channel is used - e.g is linear scaling enough?  You'll need to that to

> define a DT binding. If it turns out to be too complex, then fallback to

> specific compatibles in a generic driver to cover the ones that don't fit

> with a common scheme.  A similar case we already have is discrete

> components as analog front ends for ADCs - mostly they fall into a few

> categories and we have drivers covering those, but some are very odd indeed

> and for those ones we do have a driver even though they don't have anything

> to control as such - most extreme case being when it's a non linear analog

> sensor.

>

I actually did use a modified version of iio-rescale in my downstream code. My

use case includes an OpAmp inverter circuit placed in front of a DAC, and it's

useful for me to be able to describe this in a modular fashion, as two IIO

device tree nodes representing respectively the DAC and the OpAmp circuit

front-end.

Moreover, the LTM8054 takes a voltage on its CTL pin and infers a current

limit from it. This is also something which could be represented as a sort of

AFE node.

 LTM8054 output voltage control:          

+---+ +------------+ +--------------------+

|DAC+->Inverter AFE+->Feedback circuit AFE|

+---+ +------------+ +--------------------+

                                          

 LTM8054 output current limit control:    

+---+ +--------------------+              

|DAC+->Voltage-controller  |              

+---+ |current limiter AFE |              

      +--------------------+              

Thanks,

--

Romain Gantois, Bootlin

Embedded Linux and Kernel engineering

https://bootlin.com

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