Re: [PATCH] sky2: fix checksum bit management on some chips

[Eric Dumazet <eric.dumazet@gmail.com>]

On Wed, 2012-06-06 at 13:01 -0700, Stephen Hemminger wrote:
> The newer flavors of Yukon II use a different method for receive
> checksum offload. This is indicated in the driver by the SKY2_HW_NEW_LE
> flag. On these newer chips, the BMU_ENA_RX_CHKSUM should not be set.
> 
> The driver would get incorrectly toggle the bit, enabling the old
> checksum logic on these chips and cause a BUG_ON() assertion. If
> receive checksum was toggled via ethtool.
> 
> Reported-by: Kirill Smelkov <kirr@mns.spb.ru>
> 
> Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
> 
> ---
> Patch against net-next, please apply to net and stable kernels.
> 
> --- a/drivers/net/ethernet/marvell/sky2.c	2012-06-06 11:09:38.288440819 -0700
> +++ b/drivers/net/ethernet/marvell/sky2.c	2012-06-06 11:25:01.275782462 -0700
> @@ -4381,10 +4381,12 @@ static int sky2_set_features(struct net_
>  	struct sky2_port *sky2 = netdev_priv(dev);
>  	netdev_features_t changed = dev->features ^ features;
>  
> -	if (changed & NETIF_F_RXCSUM) {
> -		bool on = features & NETIF_F_RXCSUM;
> -		sky2_write32(sky2->hw, Q_ADDR(rxqaddr[sky2->port], Q_CSR),
> -			     on ? BMU_ENA_RX_CHKSUM : BMU_DIS_RX_CHKSUM);
> +	if ((changed & NETIF_F_RXCSUM) &&
> +	    !(sky2->hw->flags & SKY2_HW_NEW_LE)) {
> +		sky2_write32(sky2->hw,
> +			     Q_ADDR(rxqaddr[sky2->port], Q_CSR),
> +			     (features & NETIF_F_RXCSUM)
> +			     ? BMU_ENA_RX_CHKSUM : BMU_DIS_RX_CHKSUM);

Don't you need to return an error if NETIF_F_RXCSUM could not be
changed ?