netdev - RE: [RFC] r8169 : why SG / TX checksum are default disabled

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Message-ID: <3D5EE67D3FC948CAB5D11ABBBFD60A6F@realtek.com.tw>
Date:	Fri, 20 Jul 2012 10:11:17 +0800
From:	hayeswang <hayeswang@...ltek.com>
To:	'Francois Romieu' <romieu@...zoreil.com>,
	'David Miller' <davem@...emloft.net>
CC:	<eric.dumazet@...il.com>, <netdev@...r.kernel.org>
Subject: RE: [RFC] r8169 : why SG / TX checksum are default disabled

 Francois Romieu [mailto:romieu@...zoreil.com] 
[...]
> A part of the apparent problem may stem from the fact that 
> Realtek's 8168
> driver claims a modified length but it does not really skb_padto... 
> 
> Hayes, would the patch below fix the original problem ?

According to the response from our hw engineer, it still has the problem even
though you pad the packet to 60 bytes with zeroes. I would still test this patch
to verify it.

>  static netdev_tx_t rtl8169_start_xmit(struct sk_buff *skb,
> @@ -5797,7 +5804,8 @@ static netdev_tx_t 
> rtl8169_start_xmit(struct sk_buff *skb,
>  	opts[1] = cpu_to_le32(rtl8169_tx_vlan_tag(tp, skb));
>  	opts[0] = DescOwn;
>  
> -	rtl8169_tso_csum(tp, skb, opts);
> +	if (!rtl8169_tso_csum(tp, skb, opts))
> +		goto err_update_stats;
>  

I think you should check the length of opts1 of the descriptor, too. Besides,
how about the length of dma_map_xxx? Should it use the original length or the
modified length?

>  	frags = rtl8169_xmit_frags(tp, skb, opts);
>  	if (frags < 0)
> @@ -5853,6 +5861,7 @@ err_dma_1:
>  	rtl8169_unmap_tx_skb(d, tp->tx_skb + entry, txd);
>  err_dma_0:
>  	dev_kfree_skb(skb);
> +err_update_stats:
>  	dev->stats.tx_dropped++;
>  	return NETDEV_TX_OK;
>  
 
Best Regards,
Hayes

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