netdev - Re: [PATCH] net: phy: dp83869: fix default value for tx-/rx-internal-delay

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Date:   Thu, 23 Mar 2023 17:30:53 +0100
From:   Simon Horman <simon.horman@...igine.com>
To:     Josua Mayer <josua@...id-run.com>
Cc:     netdev@...r.kernel.org, Yazan Shhady <yazan.shhady@...id-run.com>,
        Andrew Lunn <andrew@...n.ch>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Russell King <linux@...linux.org.uk>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>
Subject: Re: [PATCH] net: phy: dp83869: fix default value for
 tx-/rx-internal-delay

On Thu, Mar 23, 2023 at 12:25:36PM +0200, Josua Mayer wrote:
> dp83869 internally uses a look-up table for mapping supported delays in
> nanoseconds to register values.
> When specific delays are defined in device-tree, phy_get_internal_delay
> does the lookup automatically returning an index.
> 
> The default case wrongly assigns the nanoseconds value from the lookup
> table, resulting in numeric value 2000 applied to delay configuration
> register, rather than the expected index values 0-7 (7 for 2000).
> Ultimately this issue broke RX for 1Gbps links.
> 
> Fix default delay configuration by assigning the intended index value
> directly.
> 
> Co-developed-by: Yazan Shhady <yazan.shhady@...id-run.com>
> Signed-off-by: Yazan Shhady <yazan.shhady@...id-run.com>
> Signed-off-by: Josua Mayer <josua@...id-run.com>

I wonder if this warrants:

Cc: stable@...r.kernel.org
736b25afe284 ("net: dp83869: Add RGMII internal delay configuration")

And being targeted at 'net' ([PATCH net] in subject).

In any case, the fix seems correct to me.

Reviewed-by: Simon Horman <simon.horman@...igine.com>

> ---
>  drivers/net/phy/dp83869.c | 6 ++----
>  1 file changed, 2 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/net/phy/dp83869.c b/drivers/net/phy/dp83869.c
> index b4ff9c5073a3c..9ab5eff502b71 100644
> --- a/drivers/net/phy/dp83869.c
> +++ b/drivers/net/phy/dp83869.c
> @@ -588,15 +588,13 @@ static int dp83869_of_init(struct phy_device *phydev)
>  						       &dp83869_internal_delay[0],
>  						       delay_size, true);
>  	if (dp83869->rx_int_delay < 0)
> -		dp83869->rx_int_delay =
> -				dp83869_internal_delay[DP83869_CLK_DELAY_DEF];
> +		dp83869->rx_int_delay = DP83869_CLK_DELAY_DEF;
>  
>  	dp83869->tx_int_delay = phy_get_internal_delay(phydev, dev,
>  						       &dp83869_internal_delay[0],
>  						       delay_size, false);
>  	if (dp83869->tx_int_delay < 0)
> -		dp83869->tx_int_delay =
> -				dp83869_internal_delay[DP83869_CLK_DELAY_DEF];
> +		dp83869->tx_int_delay = DP83869_CLK_DELAY_DEF;
>  
>  	return ret;
>  }
> -- 
> 2.35.3
>