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

[Andrew Lunn <andrew@lunn.ch>]

On Fri, May 30, 2025 at 01:40:38PM +0000, Christoph Stoidner wrote:
> 
> 
> 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.

I agree it is long enough, but i'm also surprised how slow the kernel
was. Are you using a fixed IP address, or dhcp?

	Andrew