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

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Message-ID: <19204ce1-f689-3295-c5a5-7f91ceac2fca@omp.ru>
Date:   Fri, 8 Oct 2021 23:13:19 +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 10/8/21 8:59 PM, Sergey Shtylyov wrote:
> On 10/8/21 9:46 AM, 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);
> [...]
>>>>> Please check the section 30.5.6.1 checksum calculation handling> And
>>>>> figure 30.25 the field of checksum attaching field
>>>>
>>>>    I have.
>>>>
>>>>> Also see Table 30.17 for checksum values for non-error conditions.
>>>>
>>>>> TCP/UDP/ICPM checksum is at last 2bytes.
>>>>
>>>>    What are you arguing with then? :-)
>>>>    My point was that your code fetched the TCP/UDP/ICMP checksum ISO
>>>> the IP checksum because it subtracts sizeof(__sum16), while should
>>>> probably subtract sizeof(__wsum)
>>>
>>> Agreed. My code missed IP4 checksum result. May be we need to extract 2
>>> checksum info from last 4 bytes.  First checksum(2bytes) is IP4 header
>>> checksum and next checksum(2 bytes)  for TCP/UDP/ICMP and use this info
>>> finding the non error case mentioned in  Table 30.17.
>>>
>>> For eg:-
>>> IPV6 non error-condition -->  "0xFFFF"-->IPV4HeaderCSum value and "0x0000"
>>> TCP/UDP/ICMP CSUM value
>>>
>>> IPV4 non error-condition -->  "0x0000"-->IPV4HeaderCSum value and "0x0000"
>>> TCP/UDP/ICMP CSUM value
>>>
>>> Do you agree?
> 
>> What I meant here is some thing like below, please let me know if you have any issues with
>> this, otherwise I would like to send the patch with below changes.
>>
>> Further improvements can happen later.
>>
>> Please let me know.
>>
>> +/* Hardware checksum status */
>> +#define IPV4_RX_CSUM_OK                0x00000000
>> +#define IPV6_RX_CSUM_OK                0xFFFF0000
> 
>    Mhm, this should prolly come from the IP headers...
> 
> [...]
>> diff --git a/drivers/net/ethernet/renesas/ravb_main.c b/drivers/net/ethernet/renesas/ravb_main.c
>> index bbb42e5328e4..d9201fbbd472 100644
>> --- a/drivers/net/ethernet/renesas/ravb_main.c
>> +++ b/drivers/net/ethernet/renesas/ravb_main.c
>> @@ -722,16 +722,18 @@ static void ravb_get_tx_tstamp(struct net_device *ndev)
>>  
>>  static void ravb_rx_csum_gbeth(struct sk_buff *skb)
>>  {
>> -       u16 *hw_csum;
>> +       u32 csum_result;
> 
>    This is not against the patch currently under investigation. :-)
> 
>> +       u8 *hw_csum;
>>  
>>         /* The hardware checksum is contained in sizeof(__sum16) (2) bytes
>>          * appended to packet data
>>          */
>> -       if (unlikely(skb->len < sizeof(__sum16)))
>> +       if (unlikely(skb->len < sizeof(__wsum)))
> 
>    I think this usage of __wsum is valid (I remember that I suggested it). We have 2 16-bit checksums here

   I meant "I don't think", of course. :-)

[...]

MBR, Sergey