linux-kernel - Re: [PATCH v3] arm64: dts: freescale: imx93-phycore-som: Delay the phy reset by a gpio

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Message-ID: <a948b903766a82897e5fc17a840ab40e29f5eda4.camel@phytec.de>
Date: Fri, 30 May 2025 13:40:38 +0000
From: Christoph Stoidner <C.Stoidner@...tec.de>
To: Andrew Lunn <andrew@...n.ch>
CC: Stefan Wahren <wahrenst@....net>, Rob Herring <robh@...nel.org>, Krzysztof
 Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, Shawn Guo
	<shawnguo@...nel.org>, Sascha Hauer <s.hauer@...gutronix.de>, Pengutronix
 Kernel Team <kernel@...gutronix.de>, Fabio Estevam <festevam@...il.com>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"imx@...ts.linux.dev" <imx@...ts.linux.dev>,
	"linux-arm-kernel@...ts.infradead.org"
	<linux-arm-kernel@...ts.infradead.org>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, "upstream@...ts.phytec.de"
	<upstream@...ts.phytec.de>
Subject: Re: [PATCH v3] arm64: dts: freescale: imx93-phycore-som: Delay the
 phy reset by a gpio



On Mi, 2025-05-28 at 21:29 +0200, Andrew Lunn wrote:
> > Yes, that's what I measured. For analysis, I added some
> > debug outputs
> > to
> > the phy reset and the 1st phy register access. And as I can see,
> > the
> > phy register access happens when userland sets up the network:
> 
> Please repeat the measurements with NFS root.
> 
> You will find that the kernel brings the interface up right have
> register_netdev() is called, and starts transmitting. It can happen
> before register_netdev() even returns.

Thanks for that hint. As you said, with nfs root the register access
happens much earlier. I measured:

       [   1.713185] DEB-PHY: mdio reset exeucted
       ...
       ...
       ...
       [   2.672892] DEB-PHY: register access

However, the delta time of 0.959707s (9597ms) still meets the T2
("prior to MDC preamble for register access") that is defined in the
PHY's datasheet with 2ms.

Seems to be fine from my point of view.

Regards,
Christoph

> 
>  Andrew