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

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Date:   Mon, 26 Oct 2020 00:51:05 +0800
From:   Icenowy Zheng <icenowy@...c.io>
To:     andrew@...n.ch, 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>,
        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



于 2020年10月25日 GMT+08:00 下午10:36:08, Andrew Lunn <andrew@...n.ch> 写到:
>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.

However, we still need to tell the MAC it's RGMII mode that is in use, not
MII/RMII/*MII. So the phy-mode still needs to be something that
contains rgmii.

>
>> 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