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Subject: Re: [PATCH] ftgmac100: Disable HW checksum generation on AST2500
To:     Vijay Khemka <vijaykhemka@fb.com>,
        "David S. Miller" <davem@davemloft.net>,
        YueHaibing <yuehaibing@huawei.com>, Andrew Lunn <andrew@lunn.ch>,
        Kate Stewart <kstewart@linuxfoundation.org>,
        Mauro Carvalho Chehab <mchehab+samsung@kernel.org>,
        Luis Chamberlain <mcgrof@kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        "netdev@vger.kernel.org" <netdev@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Cc:     "openbmc @ lists . ozlabs . org" <openbmc@lists.ozlabs.org>,
        Sai Dasari <sdasari@fb.com>,
        "linux-aspeed@lists.ozlabs.org" <linux-aspeed@lists.ozlabs.org>
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From:   Florian Fainelli <f.fainelli@gmail.com>
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Message-ID: <c9876340-c8d0-ba8b-2ae1-9900958f1834@gmail.com>
Date:   Wed, 11 Sep 2019 11:34:24 -0700
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Sender: linux-kernel-owner@vger.kernel.org
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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@lists.ozlabs.org on behalf of vijaykhemka@fb.com> wrote:
> 
>     
>     
>     On 9/10/19, 3:50 PM, "Linux-aspeed on behalf of Vijay Khemka" <linux-aspeed-bounces+vijaykhemka=fb.com@lists.ozlabs.org on behalf of vijaykhemka@fb.com> wrote:
>     
>         
>         
>         On 9/10/19, 3:05 PM, "Florian Fainelli" <f.fainelli@gmail.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?
-- 
Florian