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

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Message-ID: <OS0PR01MB59228A4BA524B092F760B52E86B39@OS0PR01MB5922.jpnprd01.prod.outlook.com>
Date:   Sat, 9 Oct 2021 08:27:17 +0000
From:   Biju Das <biju.das.jz@...renesas.com>
To:     Sergey Shtylyov <s.shtylyov@....ru>,
        "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

Hi Sergey,

> 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. :-)

Ok will use 2 * sizeof(__sum16) instead and extract IPV4 header csum and TCP/UDP/ICMP csum result.

All error condition/unsupported cases will be passed to stack with CHECKSUM_NONE
and only non-error cases will be set as CHECKSUM_UNNCESSARY.

Does it sounds good to you?

Regards,
Biju



> 
> [...]
> 
> MBR, Sergey