netdev - Re: [RFC 07/12] ravb: Fillup ravb_rx

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Message-ID: <7c31964b-8cde-50c5-d686-939b7c5bd7f0@omp.ru>
Date:   Wed, 6 Oct 2021 23:32:13 +0300
From:   Sergey Shtylyov <s.shtylyov@....ru>
To:     Biju Das <biju.das.jz@...renesas.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>
CC:     Sergei Shtylyov <sergei.shtylyov@...il.com>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Sergey Shtylyov <s.shtylyov@...russia.ru>,
        "Adam Ford" <aford173@...il.com>, Andrew Lunn <andrew@...n.ch>,
        Yuusuke Ashizuka <ashiduka@...itsu.com>,
        Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-renesas-soc@...r.kernel.org" 
        <linux-renesas-soc@...r.kernel.org>,
        Chris Paterson <Chris.Paterson2@...esas.com>,
        Biju Das <biju.das@...renesas.com>,
        Prabhakar Mahadev Lad <prabhakar.mahadev-lad.rj@...renesas.com>
Subject: Re: [RFC 07/12] ravb: Fillup ravb_rx_gbeth() stub

On 10/6/21 11:22 PM, Biju Das wrote:

[...]
>>> Fillup ravb_rx_gbeth() function to support RZ/G2L.
>>>
>>> This patch also renames ravb_rcar_rx to ravb_rx_rcar to be consistent
>>> with the naming convention used in sh_eth driver.
>>>
>>> Signed-off-by: Biju Das <biju.das.jz@...renesas.com>
>>> Reviewed-by: Lad Prabhakar
>>> <prabhakar.mahadev-lad.rj@...renesas.com>[...]
>>> diff --git a/drivers/net/ethernet/renesas/ravb_main.c
>>> b/drivers/net/ethernet/renesas/ravb_main.c
>>> index 37164a983156..42573eac82b9 100644
>>> --- a/drivers/net/ethernet/renesas/ravb_main.c
>>> +++ b/drivers/net/ethernet/renesas/ravb_main.c
>>> @@ -720,6 +720,23 @@ static void ravb_get_tx_tstamp(struct net_device
>> *ndev)
>>>  	}
>>>  }
>>>
>>> +static void ravb_rx_csum_gbeth(struct sk_buff *skb) {
>>> +	u8 *hw_csum;
>>> +
>>> +	/* The hardware checksum is contained in sizeof(__sum16) (2) bytes
>>> +	 * appended to packet data
>>> +	 */
>>> +	if (unlikely(skb->len < sizeof(__sum16)))
>>> +		return;
>>> +	hw_csum = skb_tail_pointer(skb) - sizeof(__sum16);
>>
>>    Not 32-bit? The manual says the IP checksum is stored in the first 2
>> bytes.
> 
> It is 16 bit. It is on last 2 bytes.

   So you're saying the manual is wrong?

>>
>>> +
>>> +	if (*hw_csum == 0)
>>
>>    You only check the 1st byte, not the full checksum!
> 
> As I said earlier, "0" value on last 16 bit, means no checksum error.

   How's that? 'hw_csum' is declaread as 'u8 *'!

>>> +		skb->ip_summed = CHECKSUM_UNNECESSARY;
>>> +	else
>>> +		skb->ip_summed = CHECKSUM_NONE;
>>
>>   So the TCP/UDP/ICMP checksums are not dealt with? Why enable them then?
> 
> If last 2bytes is zero, means there is no checksum error w.r.to TCP/UDP/ICMP checksums.

   Why checksum them independently then?

> RZ/G2L checksum part is different from R-Car Gen3. There is no TOE block at all for R-Car Gen3.
> 
> Regards,
> Biju

[...]

MBR, Sergey