netdev - Re: [PATCH RESEND net-next v2 1/8] dt-bindings: net: dwmac-sun8i: Clean up clock delay chain descriptions

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Message-ID: <20180513202938.GH12738@lunn.ch>
Date:   Sun, 13 May 2018 22:29:38 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     Chen-Yu Tsai <wens@...e.org>
Cc:     Giuseppe Cavallaro <peppe.cavallaro@...com>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        devicetree <devicetree@...r.kernel.org>,
        netdev <netdev@...r.kernel.org>,
        Corentin Labbe <clabbe.montjoie@...il.com>,
        Icenowy Zheng <icenowy@...c.io>,
        Maxime Ripard <maxime.ripard@...tlin.com>,
        Rob Herring <robh+dt@...nel.org>
Subject: Re: [PATCH RESEND net-next v2 1/8] dt-bindings: net: dwmac-sun8i:
 Clean up clock delay chain descriptions

On Sun, May 13, 2018 at 01:11:08PM -0700, Chen-Yu Tsai wrote:
> On Sun, May 13, 2018 at 1:05 PM, Andrew Lunn <andrew@...n.ch> wrote:
> >> > Hi Chen-Yu
> >> >
> >> > Are these delays the MAC applies? Not the PHY. It would be good to
> >> > make it clear here these are MAC imposed delays.
> >>
> >> Yes these are applied on the MAC side. Being described in the device
> >> tree bindings for the MAC, I thought this was implied to be the case?
> >> Are there known exceptions?
> >
> > There is frequent confusion with this. Most of the time, the PHY does
> > the delay, not the MAC, based on the phy-mode. So the MAC doing it is
> > an exception in itself.
> >
> > Do you actually need these delays for the board you adding support
> > for? Does the PHY not support adding the needed delays? If you don't
> > need the delays, i would not even implement them.
> 
> Yes this is already used on the Bananapi M3. This patch merely reformats
> the description and adds a note saying this only applies to RGMII mode.

Yes, the current code is needed for the Bananapi M3. But you have
another patch which extends the code to support a smaller range. Do
you have a board which actually needs this? If not, i would not add
that new code.

     Andrew