linux-kernel - Re: [PATCH v3] net: phy: add driver for Motorcomm yt8511 phy

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Date:   Fri, 14 May 2021 11:25:35 -0400
From:   Peter Geis <pgwipeout@...il.com>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     Heiner Kallweit <hkallweit1@...il.com>,
        Russell King <linux@...linux.org.uk>,
        "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>,
        "open list:ARM/Rockchip SoC..." <linux-rockchip@...ts.infradead.org>
Subject: Re: [PATCH v3] net: phy: add driver for Motorcomm yt8511 phy

On Fri, May 14, 2021 at 10:52 AM Andrew Lunn <andrew@...n.ch> wrote:
>
> > > I also wonder about bits 15:12 of PHY EXT ODH: Delay and driver
> > > strength CFG register.
> >
> > The default value *works*, and from an emi perspective we want the
> > lowest strength single that is reliable.
>
> I was not meaning signal strength, but Txc_delay_sel_fe,
>
>   selecte tx_clk_rgmii delay in chip which is used to latch txd_rgmii
>   in 100BT/10BTe mode. 150ps step. Default value 15 means about 2ns
>   clock delay compared to txd_rgmii in typical cornor.
>
> [Typos courtesy of the datasheet, not me!]
>
> This sounds like more RGMII delays. It seems like PHY EXT 0CH is about
> 1G mode, and PHY EXT 0DH is about 10/100 mode. I think you probably
> need to set this bits as well. Have you tested against a link peer at
> 10 Half? 100 Full?

Good Catch!

Guess I'll have to set that too, anything else you'd recommend looking into?

>
>    Andrew