linux-kernel - Re: [PATCH 1/2] net: ethernet: nb8800: Do not apply TX delay at MAC level

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Message-ID: <20161104151151.GF3600@lunn.ch>
Date:   Fri, 4 Nov 2016 16:11:51 +0100
From:   Andrew Lunn <andrew@...n.ch>
To:     Sebastian Frias <sf84@...oste.net>
Cc:     Måns Rullgård <mans@...sr.com>,
        "David S. Miller" <davem@...emloft.net>,
        netdev <netdev@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>, Mason <slash.tmp@...e.fr>
Subject: Re: [PATCH 1/2] net: ethernet: nb8800: Do not apply TX delay at MAC
 level

On Fri, Nov 04, 2016 at 04:02:24PM +0100, Sebastian Frias wrote:
> The delay can be applied at PHY or MAC level, but since
> PHY drivers will apply the delay at PHY level when using
> one of the "internal delay" declinations of RGMII mode
> (like PHY_INTERFACE_MODE_RGMII_TXID), applying it again
> at MAC level causes issues.
> 
> Signed-off-by: Sebastian Frias <sf84@...oste.net>
> ---
>  drivers/net/ethernet/aurora/nb8800.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/net/ethernet/aurora/nb8800.c b/drivers/net/ethernet/aurora/nb8800.c
> index b59aa35..d2855c9 100644
> --- a/drivers/net/ethernet/aurora/nb8800.c
> +++ b/drivers/net/ethernet/aurora/nb8800.c
> @@ -1282,7 +1282,7 @@ static int nb8800_tangox_init(struct net_device *dev)
>  		break;
>  
>  	case PHY_INTERFACE_MODE_RGMII_TXID:
> -		pad_mode = PAD_MODE_RGMII | PAD_MODE_GTX_CLK_DELAY;
> +		pad_mode = PAD_MODE_RGMII;
>  		break;

How many boards use this Ethernet driver? How many boards are your
potentially breaking, because they need this delay?

I guess it is a small number, because doesn't it require the PHY is
also broken, not adding a delay when it should?

     Andrew