netdev - Re: [linux-sunxi] Re: [PATCH] net: phy: realtek: omit setting PHY-side delay when "rgmii" specified

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Message-ID: <20201025143608.GD792004@lunn.ch>
Date:   Sun, 25 Oct 2020 15:36:08 +0100
From:   Andrew Lunn <andrew@...n.ch>
To:     Icenowy Zheng <icenowy@...c.io>
Cc:     Heiner Kallweit <hkallweit1@...il.com>,
        Russell King <linux@...linux.org.uk>,
        "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Willy Liu <willy.liu@...ltek.com>,
        Jernej Skrabec <jernej.skrabec@...l.net>,
        Rob Herring <robh+dt@...nel.org>, netdev@...r.kernel.org,
        devicetree@...r.kernel.org, linux-sunxi@...glegroups.com
Subject: Re: [linux-sunxi] Re: [PATCH] net: phy: realtek: omit setting
 PHY-side delay when "rgmii" specified

On Sun, Oct 25, 2020 at 10:27:05PM +0800, Icenowy Zheng wrote:
> 
> 
> 于 2020年10月25日 GMT+08:00 下午10:18:25, Andrew Lunn <andrew@...n.ch> 写到:
> >On Sun, Oct 25, 2020 at 04:55:56PM +0800, Icenowy Zheng wrote:
> >> Currently there are many boards that just set "rgmii" as phy-mode in
> >the
> >> device tree, and leave the hardware [TR]XDLY pins to set PHY delay
> >mode.
> >> 
> >> In order to keep old device tree working, omit setting delay for just
> >> "RGMII" without any internal delay suffix, otherwise many devices are
> >> broken.
> >
> >Hi Icenowy
> >
> >We have been here before with the Atheros PHY. It did not correctly
> >implement one of the delay modes, until somebody really did need that
> >mode. So the driver was fixed. And we then found a number of device
> >trees were also buggy. It was painful for a while, but all the device
> >trees got fixed.
> 
> 1. As the PHY chip has hardware configuration for configuring delays,
> we should at least have a mode that respects what's set on the hardware.

Yes, that is PHY_INTERFACE_MODE_NA. In DT, set the phy-mode to "". Or
for most MAC drivers, don't list a phy-mode at all.

> 2. As I know, at least Fedora ships a device tree with their bootloader, and
> the DT will not be updated with kernel.

I would check that. Debian does the exact opposite, the last time i
looked. It always uses the DT that come with the kernel because it
understands DT can have bugs, like all software.

      Andrew