linux-kernel - Re: [PATCH v2] ARM: imx: allow to disable board specific PHY fixups

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Date:   Tue, 31 Mar 2020 14:54:33 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     David Jander <david@...tonic.nl>
Cc:     Russell King - ARM Linux admin <linux@...linux.org.uk>,
        Florian Fainelli <f.fainelli@...il.com>,
        Oleksij Rempel <o.rempel@...gutronix.de>,
        netdev@...r.kernel.org, Sascha Hauer <s.hauer@...gutronix.de>,
        linux-kernel@...r.kernel.org, Fabio Estevam <festevam@...il.com>,
        linux-imx@....com, kernel@...gutronix.de,
        Shawn Guo <shawnguo@...nel.org>,
        linux-arm-kernel@...ts.infradead.org,
        Heiner Kallweit <hkallweit1@...il.com>
Subject: Re: [PATCH v2] ARM: imx: allow to disable board specific PHY fixups

>  - Disable the SmartEEE feature of the phy. The comment in the code implies
>    that for some reason it doesn't work, but the reason itself is not given.
>    Anyway, disabling SmartEEE should IMHO opinion be controlled by a DT
>    setting. There is no reason to believe this problem is specific to the
>    i.MX6. Besides, it is a feature of the phy, so it seems logical to expose
>    that via the DT. Once that is done, it has no place here.

The device tree properties are defined:

bindings/net/ethernet-phy.yaml:  eee-broken-100tx:
bindings/net/ethernet-phy.yaml:  eee-broken-1000t:
bindings/net/ethernet-phy.yaml:  eee-broken-10gt:
bindings/net/ethernet-phy.yaml:  eee-broken-1000kx:
bindings/net/ethernet-phy.yaml:  eee-broken-10gkx4:
bindings/net/ethernet-phy.yaml:  eee-broken-10gkr:

And there is a helper:

void of_set_phy_eee_broken(struct phy_device *phydev)

>  - Enable TXC delay. To clarify, the RGMII specification version 1 specified
>    that the RXC and TXC traces should be routed long enough to introduce a
>    certain delay to the clock signal, or the delay should be introduced via
>    other means. In a later version of the spec, a provision was given for MAC
>    or PHY devices to generate this delay internally. The i.MX6 MAC interface
>    is unable to generate the required delay internally, so it has to be taken
>    care of either by the board layout, or by the PHY device. This is the
>    crucial point: The amount of delay set by the PHY delay register depends on
>    the board layout. It should NEVER be hard-coded in SoC setup code. The
>    correct way is to specify it in the DT. Needless to say that this too,
>    isn't i.MX6-specific.

Correct:

      # RX and TX delays are added by the MAC when required
      - rgmii

      # RGMII with internal RX and TX delays provided by the PHY,
      # the MAC should not add the RX or TX delays in this case
      - rgmii-id

      # RGMII with internal RX delay provided by the PHY, the MAC
      # should not add an RX delay in this case
      - rgmii-rxid

      # RGMII with internal TX delay provided by the PHY, the MAC
      # should not add an TX delay in this case
      - rgmii-txid

The needed properties exist.

I think part of the issue is that there are iMX6 board which are not
device tree?

       Andrew