netdev - Re: [PATCH net-next 08/12] net: pse-pd: pd692x0: Add support for PSE PI priority feature

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Message-ID: <ZwU6QuGSbWF36hhF@pengutronix.de>
Date: Tue, 8 Oct 2024 15:57:22 +0200
From: Oleksij Rempel <o.rempel@...gutronix.de>
To: Andrew Lunn <andrew@...n.ch>
Cc: Kory Maincent <kory.maincent@...tlin.com>,
	"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>,
	Donald Hunter <donald.hunter@...il.com>,
	Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
	linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
	linux-doc@...r.kernel.org, Kyle Swenson <kyle.swenson@....tech>,
	Dent Project <dentproject@...uxfoundation.org>,
	kernel@...gutronix.de
Subject: Re: [PATCH net-next 08/12] net: pse-pd: pd692x0: Add support for PSE
 PI priority feature

On Thu, Oct 03, 2024 at 01:41:02AM +0200, Andrew Lunn wrote:
> > +	msg = pd692x0_msg_template_list[PD692X0_MSG_SET_PORT_PARAM];
> > +	msg.sub[2] = id;
> > +	/* Controller priority from 1 to 3 */
> > +	msg.data[4] = prio + 1;
> 
> Does 0 have a meaning? It just seems an odd design if it does not.

0 is not documented. But there are sub-priority which are not directly
configured by user, but affect the system behavior.

Priority#: Critical – 1; high – 2; low – 3
 For ports with the same priority, the PoE Controller sets the
 sub-priority according to the logic port number. (Lower number gets
 higher priority).

Port priority affects:
1. Power-up order: After a reset, the ports are powered up according to
 their priority, highest to lowest, highest priority will power up first.
2. Shutdown order: When exceeding the power budget, lowest priority
 ports will turn off first.

Should we return sub priorities on the prio get request?

If i see it correctly, even if user do not actively configures priorities,
they are always present. For example port 0 will have always a Prio
higher than Port 10.

Regards,
Oleksij
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