linux-kernel - Re: [PATCH RFC v2 1/5] dt-bindings: net: dwmac-meson: use picoseconds for the RGMII RX delay

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Message-ID: <20201215134038.GA3702703@robh.at.kernel.org>
Date:   Tue, 15 Dec 2020 07:40:38 -0600
From:   Rob Herring <robh@...nel.org>
To:     Martin Blumenstingl <martin.blumenstingl@...glemail.com>
Cc:     davem@...emloft.net, kuba@...nel.org,
        linux-amlogic@...ts.infradead.org, devicetree@...r.kernel.org,
        netdev@...r.kernel.org, jianxin.pan@...ogic.com,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        khilman@...libre.com, Neil Armstrong <narmstrong@...libre.com>,
        jbrunet@...libre.com, andrew@...n.ch, f.fainelli@...il.com
Subject: Re: [PATCH RFC v2 1/5] dt-bindings: net: dwmac-meson: use
 picoseconds for the RGMII RX delay

On Sun, Dec 13, 2020 at 05:59:05PM +0100, Martin Blumenstingl wrote:
> Hi Rob,
> 
> On Mon, Dec 7, 2020 at 8:17 PM Rob Herring <robh@...nel.org> wrote:
> >
> > On Sun, Nov 15, 2020 at 07:52:06PM +0100, Martin Blumenstingl wrote:
> > > Amlogic Meson G12A, G12B and SM1 SoCs have a more advanced RGMII RX
> > > delay register which allows picoseconds precision. Deprecate the old
> > > "amlogic,rx-delay-ns" in favour of a new "amlogic,rgmii-rx-delay-ps"
> > > property.
> > >
> > > For older SoCs the only known supported values were 0ns and 2ns. The new
> > > SoCs have 200ps precision and support RGMII RX delays between 0ps and
> > > 3000ps.
> > >
> > > While here, also update the description of the RX delay to indicate
> > > that:
> > > - with "rgmii" or "rgmii-id" the RX delay should be specified
> > > - with "rgmii-id" or "rgmii-rxid" the RX delay is added by the PHY so
> > >   any configuration on the MAC side is ignored
> > > - with "rmii" the RX delay is not applicable and any configuration is
> > >   ignored
> > >
> > > Signed-off-by: Martin Blumenstingl <martin.blumenstingl@...glemail.com>
> > > ---
> > >  .../bindings/net/amlogic,meson-dwmac.yaml     | 61 +++++++++++++++++--
> > >  1 file changed, 56 insertions(+), 5 deletions(-)
> >
> > Don't we have common properties for this now?
> I did a quick:
> $ grep -R rx-delay Documentation/devicetree/bindings/net/
> 
> I could find "rx-delay" without vendor prefix, but that's not using
> any unit in the name (ns, ps, ...)
> Please let me know if you aware of any "generic" property for the RX
> delay in picosecond precision

{rx,tx}-internal-delay-ps in ethernet-controller.yaml and 
ethernet-phy.yaml.