linux-kernel - Re: [PATCH net-next v2 3/3] net: pse-pd: pd692x0: Preserve PSE configuration across reboots

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Message-ID: <aO5Y9_7OxF9mH8wb@horms.kernel.org>
Date: Tue, 14 Oct 2025 15:06:47 +0100
From: Simon Horman <horms@...nel.org>
To: Kory Maincent <kory.maincent@...tlin.com>
Cc: Oleksij Rempel <o.rempel@...gutronix.de>,
	Andrew Lunn <andrew+netdev@...n.ch>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
	kernel@...gutronix.de,
	Dent Project <dentproject@...uxfoundation.org>,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next v2 3/3] net: pse-pd: pd692x0: Preserve PSE
 configuration across reboots

On Tue, Oct 14, 2025 at 11:56:59AM +0200, Kory Maincent wrote:
> On Tue, 14 Oct 2025 09:58:56 +0100
> Simon Horman <horms@...nel.org> wrote:
> 
> > On Mon, Oct 13, 2025 at 04:05:33PM +0200, Kory Maincent wrote:
> > > From: Kory Maincent (Dent Project) <kory.maincent@...tlin.com>
> > > 
> > > Detect when PSE hardware is already configured (user byte == 42) and
> > > skip hardware initialization to prevent power interruption to connected
> > > devices during system reboots.
> > > 
> > > Previously, the driver would always reconfigure the PSE hardware on
> > > probe, causing a port matrix reflash that resulted in temporary power
> > > loss to all connected devices. This change maintains power continuity
> > > by preserving existing configuration when the PSE has been previously
> > > initialized.
> > > 
> > > Signed-off-by: Kory Maincent <kory.maincent@...tlin.com>  
> > 
> > Hi Kory,
> > 
> > Perhaps I'm over thinking things here. But I'm wondering
> > what provision there is for a situation whereby:
> > 
> > 1. The driver configures the device
> > 2. A reboot occurs
> > 2. The (updated) driver wants to (re)configure the device
> >    with a different configuration, say because it turns
> >    out there was a bug in or enhancement to the procedure at 1.
> > 
> > ...
> 
> You have to find a way to turn off the power supply of the PSE
> controller.  As adding a devlink uAPI for this was not accepted, a hard
> reset for the PSE controller is the only way to clean the user byte
> register and (re)configure the controller at boot time.

Ok, as long as there is a way.
Maybe worth mentioning in the commit message.
But either way this patch looks good to me.

Reviewed-by: Simon Horman <horms@...nel.org>