netdev - Re: PoE complex usage of regulator API

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Message-ID: <Zi_Dnr9ye0IGoVMT@finisterre.sirena.org.uk>
Date: Tue, 30 Apr 2024 00:58:22 +0900
From: Mark Brown <broonie@...nel.org>
To: Andrew Lunn <andrew@...n.ch>
Cc: Oleksij Rempel <o.rempel@...gutronix.de>,
	Kory Maincent <kory.maincent@...tlin.com>,
	Kyle Swenson <kyle.swenson@....tech>,
	Liam Girdwood <lgirdwood@...il.com>, linux-kernel@...r.kernel.org,
	netdev@...r.kernel.org,
	Thomas Petazzoni <thomas.petazzoni@...tlin.com>
Subject: Re: PoE complex usage of regulator API

On Mon, Apr 29, 2024 at 04:57:35PM +0200, Andrew Lunn wrote:

> I was not expecting over-provisioning to happen. So prioritisation
> does not make much sense. You either have the power budget, or you
> don't. The SFP gets to use a higher power class if there is budget, or
> it is kept at a lower power class if there is no budget. I _guess_ you
> could give it a high power class, let it establish link, monitor its
> actual power consumption, and then decide to drop it to a lower class
> if the actual consumption indicates it could work at a lower
> class. But the danger is, you are going to loose link.

I suspect these devices will be like most other modern systems and
typically not consume anything like their peak current most of the time,
for networking hardware I'd imagine this will only be when the link is
saturated and could depend on factors like how long the physical links
are.  If it's anything like other similar hardware you may also be
making power requests with a very low resolution specification of the
consumption so have conservative allocation end up rejecting systems
that should work.

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