linux-kernel - Re: [PATCH] ftgmac100: Disable HW checksum generation on AST2500

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Message-ID: <76733CEB-14E1-4158-B642-5B7F74F97DE4@fb.com>
Date:   Wed, 11 Sep 2019 18:50:41 +0000
From:   Vijay Khemka <vijaykhemka@...com>
To:     Florian Fainelli <f.fainelli@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        YueHaibing <yuehaibing@...wei.com>, Andrew Lunn <andrew@...n.ch>,
        Kate Stewart <kstewart@...uxfoundation.org>,
        "Mauro Carvalho Chehab" <mchehab+samsung@...nel.org>,
        Luis Chamberlain <mcgrof@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:     "openbmc @ lists . ozlabs . org" <openbmc@...ts.ozlabs.org>,
        Sai Dasari <sdasari@...com>,
        "linux-aspeed@...ts.ozlabs.org" <linux-aspeed@...ts.ozlabs.org>
Subject: Re: [PATCH] ftgmac100: Disable HW checksum generation on AST2500



On 9/11/19, 11:34 AM, "Florian Fainelli" <f.fainelli@...il.com> wrote:

    On 9/11/19 11:30 AM, Vijay Khemka wrote:
    > 
    > 
    > On 9/10/19, 4:08 PM, "Linux-aspeed on behalf of Vijay Khemka" <linux-aspeed-bounces+vijaykhemka=fb.com@...ts.ozlabs.org on behalf of vijaykhemka@...com> wrote:
    > 
    >     
    >     
    >     On 9/10/19, 3:50 PM, "Linux-aspeed on behalf of Vijay Khemka" <linux-aspeed-bounces+vijaykhemka=fb.com@...ts.ozlabs.org on behalf of vijaykhemka@...com> wrote:
    >     
    >         
    >         
    >         On 9/10/19, 3:05 PM, "Florian Fainelli" <f.fainelli@...il.com> wrote:
    >         
    >             On 9/10/19 2:37 PM, Vijay Khemka wrote:
    >             > HW checksum generation is not working for AST2500, specially with IPV6
    >             > over NCSI. All TCP packets with IPv6 get dropped. By disabling this
    >             > it works perfectly fine with IPV6.
    >             > 
    >             > Verified with IPV6 enabled and can do ssh.
    >             
    >             How about IPv4, do these packets have problem? If not, can you continue
    >             advertising NETIF_F_IP_CSUM but take out NETIF_F_IPV6_CSUM?
    >         
    >         I changed code from (netdev->hw_features &= ~NETIF_F_HW_CSUM) to 
    >         (netdev->hw_features &= ~NETIF_F_ IPV6_CSUM). And it is not working. 
    >         Don't know why. IPV4 works without any change but IPv6 needs HW_CSUM
    >         Disabled.
    >     
    >     Now I changed to
    >     netdev->hw_features &= (~NETIF_F_HW_CSUM) | NETIF_F_IP_CSUM;
    >     And it works.
    > 
    > I investigated more on these features and found that we cannot set NETIF_F_IP_CSUM 
    > While NETIF_F_HW_CSUM is set. So I disabled NETIF_F_HW_CSUM first and enabled
    > NETIF_F_IP_CSUM in next statement. And it works fine.
    > 
    > But as per line 166 in include/linux/skbuff.h,  
    > *   NETIF_F_IP_CSUM and NETIF_F_IPV6_CSUM are being deprecated in favor of
    >  *   NETIF_F_HW_CSUM. New devices should use NETIF_F_HW_CSUM to indicate
    >  *   checksum offload capability.
    > 
    > Please suggest which of below 2 I should do. As both works for me.
    > 1. Disable completely NETIF_F_HW_CSUM and do nothing. This is original patch.
    > 2. Enable NETIF_F_IP_CSUM in addition to 1. I can have v2 if this is accepted.
    
    Sounds like 2 would leave the option of offloading IPv4 checksum
    offload, so that would be a better middle group than flat out disable
    checksum offload for both IPv4 and IPv6, no?
Sounds good, I will have v2 after lot more testing.
    -- 
    Florian