linux-kernel - Re: [PATCH 1/3] net: ethoc: don't advertise gigabit speed on attached PHY

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Message-ID: <1390817904.2735.127.camel@deadeye.wl.decadent.org.uk>
Date:	Mon, 27 Jan 2014 10:18:24 +0000
From:	Ben Hutchings <ben@...adent.org.uk>
To:	Max Filippov <jcmvbkbc@...il.com>
Cc:	linux-xtensa@...ux-xtensa.org, netdev@...r.kernel.org,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
	Chris Zankel <chris@...kel.net>,
	Marc Gauthier <marc@...ence.com>,
	"David S. Miller" <davem@...emloft.net>,
	Grant Likely <grant.likely@...aro.org>,
	Rob Herring <rob.herring@...xeda.com>
Subject: Re: [PATCH 1/3] net: ethoc: don't advertise gigabit speed on
 attached PHY

On Mon, 2014-01-27 at 07:59 +0400, Max Filippov wrote:
> OpenCores 10/100 Mbps MAC does not support speeds above 100 Mbps, but does
> not disable advertisement when PHY supports them. This results in
> non-functioning network when the MAC is connected to a gigabit PHY connected
> to a gigabit switch.
> 
> The fix is to disable gigabit speed advertisement on attached PHY
> unconditionally.
> 
> Signed-off-by: Max Filippov <jcmvbkbc@...il.com>
> ---
>  drivers/net/ethernet/ethoc.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/net/ethernet/ethoc.c b/drivers/net/ethernet/ethoc.c
> index 4de8cfd..0aa1a05 100644
> --- a/drivers/net/ethernet/ethoc.c
> +++ b/drivers/net/ethernet/ethoc.c
> @@ -712,6 +712,8 @@ static int ethoc_open(struct net_device *dev)
>  		netif_start_queue(dev);
>  	}
>  
> +	priv->phy->advertising &= ~(ADVERTISED_1000baseT_Full |
> +				    ADVERTISED_1000baseT_Half);
>  	phy_start(priv->phy);
>  	napi_enable(&priv->napi);
>  

This is not sufficient to disable gigabit speeds; the supported mask
should also be limited.  And it should be done even before the net
device is registered.

Rather than poking into the phy_device structure directly from this
driver, I think you should add a function in phylib for this purpose.

Ben.

-- 
Ben Hutchings
If at first you don't succeed, you're doing about average.

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