netdev - Re: [PATCH 1/1] net: phy: meson-gxl: Add generic dummy stubs for MMD register access

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Date:   Sun, 29 Jan 2023 11:26:34 +0100
From:   Heiner Kallweit <hkallweit1@...il.com>
To:     Chris Healy <cphealy@...il.com>, andrew@...n.ch,
        linux@...linux.org.uk, davem@...emloft.net,
        neil.armstrong@...aro.org, khilman@...libre.com,
        netdev@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-amlogic@...ts.infradead.org, linux-kernel@...r.kernel.org,
        jeremy.wang@...ogic.com
Cc:     Chris Healy <healych@...zon.com>
Subject: Re: [PATCH 1/1] net: phy: meson-gxl: Add generic dummy stubs for MMD
 register access

On 29.01.2023 03:26, Chris Healy wrote:
> From: Chris Healy <healych@...zon.com>
> 
Hi Chris,

> The Meson G12A Internal PHY does not support standard IEEE MMD extended
> register access, therefore add generic dummy stubs to fail the read and
> write MMD calls. This is necessary to prevent the core PHY code from
> erroneously believing that EEE is supported by this PHY even though this
> PHY does not support EEE, as MMD register access returns all FFFFs.
> 
> Signed-off-by: Chris Healy <healych@...zon.com>
> ---
>  drivers/net/phy/meson-gxl.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/net/phy/meson-gxl.c b/drivers/net/phy/meson-gxl.c
> index c49062ad72c6..5e41658b1e2f 100644
> --- a/drivers/net/phy/meson-gxl.c
> +++ b/drivers/net/phy/meson-gxl.c
> @@ -271,6 +271,8 @@ static struct phy_driver meson_gxl_phy[] = {
>  		.handle_interrupt = meson_gxl_handle_interrupt,
>  		.suspend        = genphy_suspend,
>  		.resume         = genphy_resume,
> +		.read_mmd	= genphy_read_mmd_unsupported,
> +		.write_mmd	= genphy_write_mmd_unsupported,
>  	},
>  };
>  

thanks for catching this. The same issue we may have for the GXL-internal PHY.
Did you check this?

One result of the issue is the invalid ethtool --show-eee output given below.
Therefore the patch should go to stable, please annotate it as [PATCH net].

Fixes tag should be:
5c3407abb338 ("net: phy: meson-gxl: add g12a support")


EEE settings for eth0:
        EEE status: enabled - active
        Tx LPI: 1000000 (us)
        Supported EEE link modes:  100baseT/Full
                                   1000baseT/Full
                                   10000baseT/Full
                                   1000baseKX/Full
                                   10000baseKX4/Full
                                   10000baseKR/Full
        Advertised EEE link modes:  100baseT/Full
                                    1000baseT/Full
                                    10000baseT/Full
                                    1000baseKX/Full
                                    10000baseKX4/Full
                                    10000baseKR/Full
        Link partner advertised EEE link modes:  100baseT/Full
                                                 1000baseT/Full
                                                 10000baseT/Full
                                                 1000baseKX/Full
                                                 10000baseKX4/Full
                                                 10000baseKR/Full