linux-kernel - Re: [PATCH net-next v2 8/8] net: pse-pd: Add PD692x0 PSE controller driver

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Date: Thu, 21 Dec 2023 17:10:00 +0100
From: Köry Maincent <kory.maincent@...tlin.com>
To: Mark Brown <broonie@...nel.org>
Cc: Oleksij Rempel <o.rempel@...gutronix.de>, "David S. Miller"
 <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski
 <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, Jonathan Corbet
 <corbet@....net>, Luis Chamberlain <mcgrof@...nel.org>, Russ Weight
 <russ.weight@...ux.dev>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
 "Rafael J. Wysocki" <rafael@...nel.org>, Rob Herring <robh+dt@...nel.org>,
 Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>, Conor Dooley
 <conor+dt@...nel.org>, Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
 netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-doc@...r.kernel.org, devicetree@...r.kernel.org, Dent Project
 <dentproject@...uxfoundation.org>, Liam Girdwood <lgirdwood@...il.com>
Subject: Re: [PATCH net-next v2 8/8] net: pse-pd: Add PD692x0 PSE controller
 driver

On Thu, 21 Dec 2023 15:43:21 +0000
Mark Brown <broonie@...nel.org> wrote:

> On Thu, Dec 21, 2023 at 04:36:10PM +0100, Köry Maincent wrote:
> > Mark Brown <broonie@...nel.org> wrote:  
> 
> > > OK...  I mean, if they're not using the regulator framework I'm not sure
> > > it has much impact - there are plenty of internal regulators in devices
> > > already so it wouldn't be *too* unusual other than the fact that AFAICT
> > > this is somewhat split between devices within the subsystem?  Neither of
> > > the messages was super clear.  
> 
> > PSE Power Interface (which is kind of the RJ45 in PSE world) have similar
> > functionalities as regulators. We wondered if registering a regulator for
> > each PSE PI (RJ45 ports) is a good idea. The point is that the PSE
> > controller driver will be its own regulator consumer.
> > I can't find any example in Linux with such a case of a driver being a
> > provider and a consumer of its own regulator. This idea of a regulator
> > biting its own tail seems weird to me. Maybe it is better to implement the
> > PSE functionalities even if they are like the regulator functionalities.  
> 
> Is it at all plausible that a system (perhaps an embedded one) might use
> something other than PSE?

Do you mean to supply power to a RJ45 port?
This can be done with a simple regulator. In that case we use the pse_regulator
driver which is a regulator consumer.
I don't know about other cases. Oleksij do you?

Regards,
-- 
Köry Maincent, Bootlin
Embedded Linux and kernel engineering
https://bootlin.com