linux-kernel - Re: [PATCH] net: phy: micrel: make *-skew-ps check more lenient

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Date:   Wed, 13 Oct 2021 08:25:50 +0000
From:   Philippe Schenker <philippe.schenker@...adex.com>
To:     "matthias.schiffer@...tq-group.com" 
        <matthias.schiffer@...tq-group.com>,
        "linux@...linux.org.uk" <linux@...linux.org.uk>,
        "hkallweit1@...il.com" <hkallweit1@...il.com>,
        "andrew@...n.ch" <andrew@...n.ch>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "kuba@...nel.org" <kuba@...nel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [PATCH] net: phy: micrel: make *-skew-ps check more lenient

On Tue, 2021-10-12 at 12:34 +0200, Matthias Schiffer wrote:
> It seems reasonable to fine-tune only some of the skew values when
> using
> one of the rgmii-*id PHY modes, and even when all skew values are
> specified, using the correct ID PHY mode makes sense for documentation
> purposes. Such a configuration also appears in the binding docs in
> Documentation/devicetree/bindings/net/micrel-ksz90x1.txt, so the
> driver
> should not warn about it.

I don't think your commit message is right. The rgmii-*id PHY modes are
no longer just for documentation purposes on KSZ9031 PHY. They are used
to set the skew-registers according to .

The warning is there, that in case you override the skew registers of
one of the modes rgmii-id, rgmii-txid, rgmii-rxid with *-skew-ps
settings in DT.

Therefore I also think the warning is valuable and should be kept. We
may want to reword it though.

Philippe

> 
> Signed-off-by: Matthias Schiffer <matthias.schiffer@...tq-group.com>
> ---
>  drivers/net/phy/micrel.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/phy/micrel.c b/drivers/net/phy/micrel.c
> index c330a5a9f665..03e58ebf68af 100644
> --- a/drivers/net/phy/micrel.c
> +++ b/drivers/net/phy/micrel.c
> @@ -863,9 +863,9 @@ static int ksz9031_config_init(struct phy_device
> *phydev)
>                                 MII_KSZ9031RN_TX_DATA_PAD_SKEW, 4,
>                                 tx_data_skews, 4, &update);
>  
> -               if (update && phydev->interface !=
> PHY_INTERFACE_MODE_RGMII)
> +               if (update && !phy_interface_is_rgmii(phydev))
>                         phydev_warn(phydev,
> -                                   "*-skew-ps values should be used
> only with phy-mode = \"rgmii\"\n");
> +                                   "*-skew-ps values should be used
> only with RGMII PHY modes\n");
>  
>                 /* Silicon Errata Sheet (DS80000691D or DS80000692D):
>                  * When the device links in the 1000BASE-T slave mode
> only,