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

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Message-ID: <CAFBinCDXqnPQtu4ZQW2ngxKVSbRQNFbnhy6M04gE+Mc8HOTM8g@mail.gmail.com>
Date:   Sun, 13 Dec 2020 17:59:05 +0100
From:   Martin Blumenstingl <martin.blumenstingl@...glemail.com>
To:     Rob Herring <robh@...nel.org>
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

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


Best regards,
Martin