linux-kernel - Re: [PATCH 2/4] phy: s32g: Add serdes subsystem phy

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Message-ID: <aXtvDn_-pCuKPrnf@vaman>
Date: Thu, 29 Jan 2026 20:00:38 +0530
From: Vinod Koul <vkoul@...nel.org>
To: "Russell King (Oracle)" <linux@...linux.org.uk>
Cc: Vincent Guittot <vincent.guittot@...aro.org>, neil.armstrong@...aro.org,
	Simon Horman <horms@...nel.org>, krzk+dt@...nel.org,
	conor+dt@...nel.org, ciprianmarian.costea@....nxp.com, s32@....com,
	p.zabel@...gutronix.de, ghennadi.procopciuc@....com,
	Ionut.Vicovan@....com, linux-phy@...ts.infradead.org,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, netdev@...r.kernel.org,
	Frank.li@....com
Subject: Re: [PATCH 2/4] phy: s32g: Add serdes subsystem phy

On 29-01-26, 13:51, Russell King (Oracle) wrote:
> On Thu, Jan 29, 2026 at 02:36:01PM +0100, Vincent Guittot wrote:
> > On Thu, 29 Jan 2026 at 14:23, Russell King (Oracle)
> > <linux@...linux.org.uk> wrote:
> > >
> > > On Thu, Jan 29, 2026 at 02:01:13PM +0100, Vincent Guittot wrote:
> > > > yes, the usual pattern is :
> > > > - phy_set_mode_ext()
> > > > - then phy_power_on()
> > > > but I can add an additional check
> > >
> > > Please read Documentation/driver-api/phy/phy.rst section "Order of API
> > > calls" which suggests phy_set_mode_ext() after phy_power_on().
> > 
> > Fair enough.
> > That being said, all pcie drivers  that use phy_set_mode_ext(), call
> > it before phy_power_on()
> 
> It looks like many ethernet drivers do the same, so I think maybe the
> generic PHY documentation is incorrect or misleading, or is expressing
> a preference that almost no one follows. Something for the generic PHY
> maintainers to look at and/or comment on.

I would feel it makes sense to configure the mode first and then power
the phy up. As commented above yes it looks like apart from one tegra
driver rest seem to do it this way.

Lets update the documentation

-- 
~Vinod