netdev - RE: [PATCH net-next 2/5] net: enetc: add Tx checksum offload for i.MX95 ENETC

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Message-ID:
 <PAXPR04MB85105409DFD9E82A8EE1528B885D2@PAXPR04MB8510.eurprd04.prod.outlook.com>
Date: Fri, 8 Nov 2024 01:32:12 +0000
From: Wei Fang <wei.fang@....com>
To: Frank Li <frank.li@....com>
CC: Claudiu Manoil <claudiu.manoil@....com>, Vladimir Oltean
	<vladimir.oltean@....com>, Clark Wang <xiaoning.wang@....com>,
	"andrew+netdev@...n.ch" <andrew+netdev@...n.ch>, "davem@...emloft.net"
	<davem@...emloft.net>, "edumazet@...gle.com" <edumazet@...gle.com>,
	"kuba@...nel.org" <kuba@...nel.org>, "pabeni@...hat.com" <pabeni@...hat.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"imx@...ts.linux.dev" <imx@...ts.linux.dev>
Subject: RE: [PATCH net-next 2/5] net: enetc: add Tx checksum offload for
 i.MX95 ENETC

> 
> On Thu, Nov 07, 2024 at 11:38:14AM +0800, Wei Fang wrote:
> > In addition to supporting Rx checksum offload, i.MX95 ENETC also
> > supports Tx checksum offload. The transmit checksum offload is
> > implemented through the Tx BD. To support Tx checksum offload,
> > software needs to fill some auxiliary information in Tx BD, such as IP
> > version, IP header offset and size, whether L4 is UDP or TCP, etc.
> 
> Add empty line here
> 
> > Same as Rx checksum offload, Tx checksum offload capability isn't
> > defined in register, so tx_csum bit is added to struct enetc_drvdata
> > to indicate whether the device supports Tx checksum offload.
> >
> > Signed-off-by: Wei Fang <wei.fang@....com>
> > ---
> >  drivers/net/ethernet/freescale/enetc/enetc.c  | 52
> > ++++++++++++++++---  drivers/net/ethernet/freescale/enetc/enetc.h  |  2
> +
> >  .../net/ethernet/freescale/enetc/enetc_hw.h   | 14 +++--
> >  .../freescale/enetc/enetc_pf_common.c         |  3 ++
> >  4 files changed, 61 insertions(+), 10 deletions(-)
> >
> > diff --git a/drivers/net/ethernet/freescale/enetc/enetc.c
> > b/drivers/net/ethernet/freescale/enetc/enetc.c
> > index 3137b6ee62d3..f98d14841838 100644
> > --- a/drivers/net/ethernet/freescale/enetc/enetc.c
> > +++ b/drivers/net/ethernet/freescale/enetc/enetc.c
> > @@ -143,6 +143,26 @@ static int enetc_ptp_parse(struct sk_buff *skb, u8
> *udp,
> >  	return 0;
> >  }
> >
> > +static bool enetc_tx_csum_offload_check(struct sk_buff *skb) {
> > +	if (ip_hdr(skb)->version == 4)
> > +		return ip_hdr(skb)->protocol == IPPROTO_TCP ||
> > +		       ip_hdr(skb)->protocol == IPPROTO_UDP;
> > +	else if (ip_hdr(skb)->version == 6)
> 
> needn't else
> 
> > +		return ipv6_hdr(skb)->nexthdr == NEXTHDR_TCP ||
> > +		       ipv6_hdr(skb)->nexthdr == NEXTHDR_UDP;
> > +	else
> 
> needn't else, I remember some compiler check will report warning.
> 

I'm not sure whether other compilers complain warning, but I can
refine this helper function.

> > +		return false;
> > +}
> > +
> > +static bool enetc_skb_is_tcp(struct sk_buff *skb) {
> > +	if (ip_hdr(skb)->version == 4)
> > +		return ip_hdr(skb)->protocol == IPPROTO_TCP;
> > +	else
> > +		return ipv6_hdr(skb)->nexthdr == NEXTHDR_TCP; }
> > +
> >  static int enetc_map_tx_buffs(struct enetc_bdr *tx_ring, struct
> > sk_buff *skb)  {
> >  	bool do_vlan, do_onestep_tstamp = false, do_twostep_tstamp = false;
> > @@ -160,6 +180,29 @@ static int enetc_map_tx_buffs(struct enetc_bdr
> *tx_ring, struct sk_buff *skb)
> >  	dma_addr_t dma;
> >  	u8 flags = 0;
> >
> > +	enetc_clear_tx_bd(&temp_bd);
> > +	if (skb->ip_summed == CHECKSUM_PARTIAL) {
> > +		/* Can not support TSD and checksum offload at the same time */
> > +		if (priv->active_offloads & ENETC_F_TXCSUM &&
> > +		    enetc_tx_csum_offload_check(skb) && !tx_ring->tsd_enable) {
> > +			bool is_ipv6 = ip_hdr(skb)->version == 6;
> > +			bool is_tcp = enetc_skb_is_tcp(skb);
> > +
> > +			temp_bd.l3_start = skb_network_offset(skb);
> > +			temp_bd.ipcs = is_ipv6 ? 0 : 1;
> > +			temp_bd.l3_hdr_size = skb_network_header_len(skb) / 4;
> > +			temp_bd.l3t = is_ipv6 ? 1 : 0;
> > +			temp_bd.l4t = is_tcp ? ENETC_TXBD_L4T_TCP :
> ENETC_TXBD_L4T_UDP;
> > +			flags |= ENETC_TXBD_FLAGS_CSUM_LSO |
> ENETC_TXBD_FLAGS_L4CS;
> > +		} else {
> > +			if (skb_checksum_help(skb)) {
> > +				dev_err(tx_ring->dev, "skb_checksum_help() error\n");
> > +
> > +				return 0;
> > +			}
> > +		}
> > +	}
> > +
> >  	i = tx_ring->next_to_use;
> >  	txbd = ENETC_TXBD(*tx_ring, i);
> >  	prefetchw(txbd);
> > @@ -170,7 +213,6 @@ static int enetc_map_tx_buffs(struct enetc_bdr
> > *tx_ring, struct sk_buff *skb)
> >
> >  	temp_bd.addr = cpu_to_le64(dma);
> >  	temp_bd.buf_len = cpu_to_le16(len);
> > -	temp_bd.lstatus = 0;
> 
> not sure why remove clean lstatus here.
> 

Below is the snippet of Tx BD format, set lstatus to 0 will clear
the auxiliary information for LSO, due to we have cleared the
entire Tx BD at the beginning (enetc_clear_tx_bd(&temp_bd)).
So it is safe to remove lstatus.

union {
	struct {
		u8 l3_start:7;
		u8 ipcs:1;
		u8 l3_hdr_size:7;
		u8 l3t:1;
		u8 resv:5;
		u8 l4t:3;
		u8 flags;
	}; /* default layout */
	__le32 txstart;
	__le32 lstatus;
};