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

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Date: Wed, 27 Mar 2024 23:02:52 +0100
From: Andreas Kemnade <andreas@...nade.info>
To: Matti Vaittinen <mazziesaccount@...il.com>
Cc: lee@...nel.org, robh+dt@...nel.org, krzysztof.kozlowski+dt@...aro.org,
 conor+dt@...nel.org, devicetree@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/2] mfd: rohm-bd71828: Add power off functionality

Hi Matti,

On Wed, 27 Mar 2024 16:11:36 +0200
Matti Vaittinen <mazziesaccount@...il.com> wrote:

> On 3/27/24 15:04, Andreas Kemnade wrote:
> > Hi,
> > 
> > On Wed, 27 Mar 2024 09:32:29 +0200
> > Matti Vaittinen <mazziesaccount@...il.com> 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.

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

Regards,
Andreas