Message-ID: <20241105112010.17d6f40b@kmaincent-XPS-13-7390>
Date: Tue, 5 Nov 2024 11:20:10 +0100
From: Kory Maincent <kory.maincent@...tlin.com>
To: Oleksij Rempel <o.rempel@...gutronix.de>
Cc: Andrew Lunn <andrew@...n.ch>, "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>, Rob Herring <robh@...nel.org>, Andrew Lunn
 <andrew+netdev@...n.ch>, Simon Horman <horms@...nel.org>, Heiner Kallweit
 <hkallweit1@...il.com>, Russell King <linux@...linux.org.uk>, Liam Girdwood
 <lgirdwood@...il.com>, Mark Brown <broonie@...nel.org>, 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, Maxime Chevallier <maxime.chevallier@...tlin.com>
Subject: Re: [PATCH RFC net-next v2 15/18] net: pse-pd: Add support for
 getting and setting port priority

On Fri, 1 Nov 2024 11:23:06 +0100
Oleksij Rempel <o.rempel@...gutronix.de> wrote:

> On Fri, Nov 01, 2024 at 09:31:43AM +0100, Oleksij Rempel wrote:
> > On Thu, Oct 31, 2024 at 12:11:04PM +0100, Kory Maincent wrote:  
> > > On Thu, 31 Oct 2024 07:54:08 +0100
> > > Oleksij Rempel <o.rempel@...gutronix.de> wrote:
> > >   
>  [...]  
>  [...]  
> > > 
> > > Ack. So we assume PoDL could have the same interruption events.
> > >   
>  [...]  
> > 
> > After thinking about it more overnight, I wanted to revisit the idea of
> > having a priority strategy per port. Right now, if one port is set to
> > static or dynamic mode, all disabled ports seem to have to follow it
> > somehow too. This makes it feel like we should have a strategy for the
> > whole power domain, not just for each port.
> > 
> > I'm having trouble imagining how a per-port priority strategy would work in
> > this setup.

Indeed you are right. I was first thinking of using the same port priority for
all the ports of a PSE but it seems indeed better to have it by Power domain.

> > Another point that came to mind is that we might have two different
> > components here, and we need to keep these two parts separate in follow-up
> > discussions:
> > 
> > - **Budget Evaluation Strategy**: The static approach seems
> > straightforward—if a class requests more than available, appropriate
> > actions are taken. However, the dynamic approach has more complexity, such
> > as determining the threshold, how long violations can be tolerated, and
> > whether a safety margin should be maintained before exceeding maximum load.
> > 
> > - **Disconnection Policy**: Once a budget violation is detected, this
> > decides how to react, like which ports should be disconnected and in what
> > order.
> > 
> > Would it make more sense to have a unified strategy for power domains,
> > where we apply the same budget evaluation mode (static or dynamic) and
> > disconnection policy to all ports in that domain? This could make the
> > configuration simpler and the power management more predictable.  

Yes, these policies and the port priority mode should be per power domains. 

> Except of user reports, do we have documented confirmation about dynamic
> Budget Evaluation Strategy in PD692x0 firmware?
> 
> Do this configuration bits are what I called Budget Evaluation Strategy?
> Version 3.55:
> Bits [3..0]—BT port PM mode
> 0x0: The port power that is used for power management purposes is
>      dynamic (Iport x Vmain).

Yes it seems so. I can't find any more configurations on the budget evaluation
strategy than the power limit.

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

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