netdev - Re: [PATCH v4 net-next 2/2] ravb: Add Tx checksum offload support for GbEth

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Message-ID: <76b13c41-9f0b-daf2-9aa8-7fdaf489fe0a@omp.ru>
Date: Mon, 5 Feb 2024 23:27:13 +0300
From: Sergey Shtylyov <s.shtylyov@....ru>
To: Biju Das <biju.das.jz@...renesas.com>, "David S. Miller"
	<davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski
	<kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>
CC: Claudiu Beznea <claudiu.beznea.uj@...renesas.com>, Yoshihiro Shimoda
	<yoshihiro.shimoda.uh@...esas.com>, Wolfram Sang
	<wsa+renesas@...g-engineering.com>, Nikita Yushchenko
	<nikita.yoush@...entembedded.com>, <netdev@...r.kernel.org>,
	<linux-renesas-soc@...r.kernel.org>, Geert Uytterhoeven
	<geert+renesas@...der.be>, Prabhakar Mahadev Lad
	<prabhakar.mahadev-lad.rj@...renesas.com>, Biju Das <biju.das.au@...il.com>
Subject: Re: [PATCH v4 net-next 2/2] ravb: Add Tx checksum offload support for
 GbEth

On 2/3/24 5:25 PM, Biju Das wrote:

> TOE has hardware support for calculating IP header and TCP/UDP/ICMP
> checksum for both IPv4 and IPv6.
> 
> Add Tx checksum offload supported by TOE for IPv4 and TCP/UDP.
> 
> For Tx, the result of checksum calculation is set to the checksum field of
> each IPv4 Header/TCP/UDP/ICMP of ethernet frames. For the unsupported
> frames, those fields are not changed. If a transmission frame is an UDPv4
> frame and its checksum value in the UDP header field is 0x0000, TOE does
> not calculate checksum for UDP part of this frame as it is optional
> function as per standards.
> 
> We can test this functionality by the below commands
> 
> ethtool -K eth0 tx on --> to turn on Tx checksum offload
> ethtool -K eth0 tx off --> to turn off Tx checksum offload
> 
> Signed-off-by: Biju Das <biju.das.jz@...renesas.com>
[...]

> diff --git a/drivers/net/ethernet/renesas/ravb.h b/drivers/net/ethernet/renesas/ravb.h
> index 64bf29d01ad0..d7b1c6d15a17 100644
> --- a/drivers/net/ethernet/renesas/ravb.h
> +++ b/drivers/net/ethernet/renesas/ravb.h
[...]
> @@ -981,6 +982,21 @@ enum CSR0_BIT {
>  	CSR0_RPE	= 0x00000020,
>  };
>  
> +enum CSR1_BIT {
> +	CSR1_TIP4	= 0x00000001,
> +	CSR1_TTCP4	= 0x00000010,
> +	CSR1_TUDP4	= 0x00000020,
> +	CSR1_TICMP4	= 0x00000040,
> +	CSR1_TTCP6	= 0x00100000,
> +	CSR1_TUDP6	= 0x00200000,
> +	CSR1_TICMP6	= 0x00400000,
> +	CSR1_THOP	= 0x01000000,
> +	CSR1_TROUT	= 0x02000000,
> +	CSR1_TAHD	= 0x04000000,
> +	CSR1_TDHD	= 0x08000000,
> +	CSR1_ALL	= 0x0F700071,

   I doubt we really need CSR1_ALL...

[...]
> diff --git a/drivers/net/ethernet/renesas/ravb_main.c b/drivers/net/ethernet/renesas/ravb_main.c
> index 4f310bcee7c0..fee771f14fc5 100644
> --- a/drivers/net/ethernet/renesas/ravb_main.c
> +++ b/drivers/net/ethernet/renesas/ravb_main.c
[...]
> @@ -524,16 +525,29 @@ static int ravb_ring_init(struct net_device *ndev, int q)
>  
>  static void ravb_csum_init_gbeth(struct net_device *ndev)
>  {
> -	if (!(ndev->features & NETIF_F_RXCSUM))
> +	bool tx_enable = ndev->features & NETIF_F_HW_CSUM;
> +	bool rx_enable = ndev->features & NETIF_F_RXCSUM;
> +
> +	if (!(tx_enable || rx_enable))
>  		goto done;
>  
>  	ravb_write(ndev, 0, CSR0);
> -	if (ravb_wait(ndev, CSR0, CSR0_RPE, 0)) {
> +	if (ravb_wait(ndev, CSR0, CSR0_TPE | CSR0_RPE, 0)) {
>  		netdev_err(ndev, "Timeout enabling hardware checksum\n");
> -		ndev->features &= ~NETIF_F_RXCSUM;
> +
> +		if (tx_enable)
> +			ndev->features &= ~NETIF_F_HW_CSUM;
> +
> +		if (rx_enable)
> +			ndev->features &= ~NETIF_F_RXCSUM;
>  	} else {
> -		ravb_write(ndev, CSR2_ALL & ~(CSR2_RTCP6 | CSR2_RUDP6 |
> -					      CSR2_RICMP6), CSR2);
> +		if (tx_enable)
> +			ravb_write(ndev, CSR1_ALL & ~(CSR1_TICMP4 | CSR1_TTCP6 |
> +						      CSR1_TUDP6 | CSR1_TICMP6), CSR1);

   With the v6 bits 20...22 being 0, the bits 24...27 are ignored anyway,
the manual says. So I think I'd prefer:

			ravb_write(ndev, CSR1_TIP4 | CSR1_TTCP4 | CSR1_TUDP4, CSR1);
[...]
> @@ -2418,6 +2465,18 @@ static int ravb_set_features_gbeth(struct net_device *ndev,
>  			goto done;
>  	}
>  
> +	if (changed & NETIF_F_HW_CSUM) {
> +		if (features & NETIF_F_HW_CSUM)
> +			val = CSR1_ALL & ~(CSR1_TICMP4 | CSR1_TTCP6 |
> +					   CSR1_TUDP6 | CSR1_TICMP6);

   Likewise, I'd prefer:

			val = CSR1_TIP4 | CSR1_TTCP4 | CS12_TUDP4;

[...]

MBR, Sergey