Re: [PATCH v2 2/2] mfd: rohm-bd71828: Add power off functionality

[Matti Vaittinen]

Morning Andreas,

On 3/28/24 00:02, Andreas Kemnade wrote:
> Hi Matti,
>
> On Wed, 27 Mar 2024 16:11:36 +0200
> Matti Vaittinen <mazziesaccount@xxxxxxxxx> wrote:
>
> > On 3/27/24 15:04, Andreas Kemnade wrote:
> > > Hi,
> > >
> > > On Wed, 27 Mar 2024 09:32:29 +0200
> > > Matti Vaittinen <mazziesaccount@xxxxxxxxx> wrote:
> > >    
> > > > It's worth noting that there is another PMIC, BD71879, which, from the
> > > > driver software point of view, should be (almost?) identical to the
> > > > BD71828. I believe the BD71828 drivers should work with it as well - if
> > > > not out of the box, at least with very minor modifications.
> > > > Unfortunately I don't know products where the BD71879 is used or if it
> > > > is sold via distributors - so I don't know if adding a DT
> > > > compatible/chip type define for it would be beneficial.
> > >
> > > yes, you already told we thet the BD71828 drivers are compatible with
> > > the BD71879 and I am using the latter.
> > > But that at least should be commented somewhere, so that
> > > people do not raise questions, like: Do I have some strange board revision,
> > > etc?
> > > The most terse form to comment it is a separate dt compatible so we are
> > > prepare any "almost identical" surprises.
> >
> > I agree. Reason why I haven't done this already is that I don't always
> > (like in this case) know which of the variant are eventually sold. So,
> > it's balancing dance between adding compatibles for ICs that will never
> > been seen by large audience, and missing compatibles for some of the
> > variants.
> >
> > This is also why I was interested in knowing which variant you had, and
> > where was it used.
> I have found it in the Kobo Clara 2E ebook reader.
> Kobo seems to switch from RC5T619 to BD71879.
> The Kobo Nia rev C also has that one.
> Kobo Libra 2 has several hardware revs out in the wild, some of them
> with the BD71879.

Thanks for the info :) It's a shame we so rarely know where things we 
work for are used. I always find news like this interesting.

> > But yes, I think that as the BD71879 has obviously been found by a
> > community linux kernel user - it would make sense to add a compatible
> > for it!
> >
> > Do you feel like adding the compatible 'rohm,bd71879' in
> > rohm,bd71828-pmic.yaml as part of this series(?)
>
> Do we want a separate chip_type now? Or do we want to add it later if
> we ever see a difference. My personal opinion is to wait until there is
> really a need.

Using the BD71828 chip_id for BD71879 in the MFD driver is fine to me. A 
comment saying they seem "functionally equivalent" can be added to 
explain this choice.

> If we do not need it, then it is a different series I think but sure
> I will produce such a patch.

Great, thanks! I think it's clearer to have it as own patch, but I think 
it fits in the same series - what suits you best. (Don't know if Lee or 
DT peeps have different opinion.)

Yours,
	-- Matti

--
Matti Vaittinen
Linux kernel developer at ROHM Semiconductors
Oulu Finland

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