netdev - Re: [RFC 2/2] ravb: Add Rx checksum offload support

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Date:   Wed, 24 Nov 2021 23:10:47 +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:     Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>,
        Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>,
        <netdev@...r.kernel.org>, <linux-renesas-soc@...r.kernel.org>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Chris Paterson <Chris.Paterson2@...esas.com>,
        "Biju Das" <biju.das@...renesas.com>
Subject: Re: [RFC 2/2] ravb: Add Rx checksum offload support

Hello!

On 11/23/21 4:31 PM, Biju Das wrote:

> TOE has hw support for calculating IP header checkum for IPV4 and
> TCP/UDP/ICMP checksum for both IPV4 and IPV6.
> 
> This patch adds Rx checksum offload supported by TOE.
> 
> Signed-off-by: Biju Das <biju.das.jz@...renesas.com>
> ---
>  drivers/net/ethernet/renesas/ravb.h      |  4 +++
>  drivers/net/ethernet/renesas/ravb_main.c | 31 ++++++++++++++++++++++++
>  2 files changed, 35 insertions(+)
> 
> diff --git a/drivers/net/ethernet/renesas/ravb.h b/drivers/net/ethernet/renesas/ravb.h
> index a96552348e2d..d0e5eec0636e 100644
> --- a/drivers/net/ethernet/renesas/ravb.h
> +++ b/drivers/net/ethernet/renesas/ravb.h
> @@ -44,6 +44,10 @@
>  #define RAVB_RXTSTAMP_TYPE_ALL	0x00000006
>  #define RAVB_RXTSTAMP_ENABLED	0x00000010	/* Enable RX timestamping */
>  
> +/* GbEthernet TOE hardware checksum values */
> +#define TOE_RX_CSUM_OK		0x0000
> +#define TOE_RX_CSUM_UNSUPPORTED	0xFFFF

   These are hardly needed IMO.

[...]
> diff --git a/drivers/net/ethernet/renesas/ravb_main.c b/drivers/net/ethernet/renesas/ravb_main.c
> index c2b92c6a6cd2..2533e3401593 100644
> --- a/drivers/net/ethernet/renesas/ravb_main.c
> +++ b/drivers/net/ethernet/renesas/ravb_main.c
> @@ -720,6 +720,33 @@ static void ravb_get_tx_tstamp(struct net_device *ndev)
>  	}
>  }
>  
> +static void ravb_rx_csum_gbeth(struct sk_buff *skb)
> +{
> +	u32 csum_ip_hdr, csum_proto;

   Why u32 if both sums are 16-bit?

> +	u8 *hw_csum;
> +
> +	/* The hardware checksum is contained in sizeof(__sum16) * 2 = 4 bytes
> +	 * appended to packet data. First 2 bytes is ip header csum and last
> +	 * 2 bytes is protocol csum.
> +	 */
> +	if (unlikely(skb->len < sizeof(__sum16) * 2))
> +		return;
> +	hw_csum = skb_tail_pointer(skb) - sizeof(__sum16);
> +	csum_proto = csum_unfold((__force __sum16)get_unaligned_le16(hw_csum));
> +
> +	hw_csum = skb_tail_pointer(skb) - 2 * sizeof(__sum16);
> +	csum_ip_hdr = csum_unfold((__force __sum16)get_unaligned_le16(hw_csum));
> +
> +	skb->ip_summed = CHECKSUM_NONE;
> +	if (csum_proto == TOE_RX_CSUM_OK) {
> +		if (skb->protocol == htons(ETH_P_IP) && csum_ip_hdr == TOE_RX_CSUM_OK)
> +			skb->ip_summed = CHECKSUM_UNNECESSARY;
> +		else if (skb->protocol == htons(ETH_P_IPV6) &&
> +			 csum_ip_hdr == TOE_RX_CSUM_UNSUPPORTED)
> +			skb->ip_summed = CHECKSUM_UNNECESSARY;

   Checksum is unsupported and you declare it unnecessary?

> +	}

   Now where's a call to skb_trim()?

[...]

MBR, Sergey