netdev - Re: [PATCH v2] ftgmac100: Disable HW checksum generation on AST2500

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Date:   Thu, 17 Oct 2019 12:28:41 +1100
From:   Benjamin Herrenschmidt <benh@...nel.crashing.org>
To:     Vijay Khemka <vijaykhemka@...com>,
        "David S. Miller" <davem@...emloft.net>,
        Kate Stewart <kstewart@...uxfoundation.org>,
        Sven Van Asbroeck <TheSven73@...il.com>,
        Mark Brown <broonie@...nel.org>,
        Bhupesh Sharma <bhsharma@...hat.com>,
        YueHaibing <yuehaibing@...wei.com>,
        Mauro Carvalho Chehab <mchehab+samsung@...nel.org>,
        Luis Chamberlain <mcgrof@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     "openbmc @ lists . ozlabs . org" <openbmc@...ts.ozlabs.org>,
        joel@....id.au, linux-aspeed@...ts.ozlabs.org, sdasari@...com
Subject: Re: [PATCH v2] ftgmac100: Disable HW checksum generation on AST2500

On Fri, 2019-10-11 at 14:30 -0700, 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. As it works for IPV4 so enabled
> hw checksum back for IPV4.
> 
> Verified with IPV6 enabled and can do ssh.

So while this probably works, I don't think this is the right
approach, at least according to the comments in skbuff.h

The driver should have handled unsupported csum via SW fallback
already in ftgmac100_prep_tx_csum()

Can you check why this didn't work for you ?

Cheers,
Ben.

> Signed-off-by: Vijay Khemka <vijaykhemka@...com>
> ---
> Changes since v1:
>  Enabled IPV4 hw checksum generation as it works for IPV4.
> 
>  drivers/net/ethernet/faraday/ftgmac100.c | 13 ++++++++++++-
>  1 file changed, 12 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/ethernet/faraday/ftgmac100.c
> b/drivers/net/ethernet/faraday/ftgmac100.c
> index 030fed65393e..0255a28d2958 100644
> --- a/drivers/net/ethernet/faraday/ftgmac100.c
> +++ b/drivers/net/ethernet/faraday/ftgmac100.c
> @@ -1842,8 +1842,19 @@ static int ftgmac100_probe(struct
> platform_device *pdev)
>  	/* AST2400  doesn't have working HW checksum generation */
>  	if (np && (of_device_is_compatible(np, "aspeed,ast2400-mac")))
>  		netdev->hw_features &= ~NETIF_F_HW_CSUM;
> +
> +	/* AST2500 doesn't have working HW checksum generation for IPV6
> +	 * but it works for IPV4, so disabling hw checksum and enabling
> +	 * it for only IPV4.
> +	 */
> +	if (np && (of_device_is_compatible(np, "aspeed,ast2500-mac")))
> {
> +		netdev->hw_features &= ~NETIF_F_HW_CSUM;
> +		netdev->hw_features |= NETIF_F_IP_CSUM;
> +	}
> +
>  	if (np && of_get_property(np, "no-hw-checksum", NULL))
> -		netdev->hw_features &= ~(NETIF_F_HW_CSUM |
> NETIF_F_RXCSUM);
> +		netdev->hw_features &= ~(NETIF_F_HW_CSUM |
> NETIF_F_RXCSUM
> +					 | NETIF_F_IP_CSUM);
>  	netdev->features |= netdev->hw_features;
>  
>  	/* register network device */