Message-ID: <20231221181955.422e676e@kmaincent-XPS-13-7390>
Date: Thu, 21 Dec 2023 18:19:55 +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 16:20:10 +0000
Mark Brown <broonie@...nel.org> wrote:

> On Thu, Dec 21, 2023 at 05:10:00PM +0100, Köry Maincent wrote:
> > 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?  
> 
> Whatever it is that PSE does.
> 
> > 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?  
> 
> In that case it sounds like you need the split to allow people to
> substitute in a non-PSE supply, and everything ought to be doing the
> consumer thing?

In case of non-PSE supply we would indeed have a wrapper like this
pse_regulator driver. 

My question was about PSE:
A PSE may indeed need a regulator to work properly. In that case the PSE is
indeed a consumer.
The PSE may also power one or several RJ45 ports. The power capabilities of each
port have some capabilities like regulators (enable/disable, power limit,
current and voltage status ...) and capabilities specific to PoE (class, type
...).
These capabilities are modified by ethtool which will call ops within the PSE
driver. 
As the power capabilities for each ports are kind of similar to regulator
capabilities we wonder if it is a good idea to register regulator for each ports
of a PSE to avoid rewriting the wheel.

So we will have PSE drivers which are regulators consumer for the chip,
regulator providers for all its ports and regulator consumers also for all its
ports. Is it clearer? Would that sound ok for you?

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

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