linux-kernel - Re: [PATCH v8 net-next 1/4] net: enetc: add Tx checksum offload for i.MX95 ENETC

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Message-ID: <5f2eb433-479c-49d2-bc2f-07f6c0a52c60@intel.com>
Date: Tue, 17 Dec 2024 16:13:13 +0100
From: Alexander Lobakin <aleksander.lobakin@...el.com>
To: Wei Fang <wei.fang@....com>
CC: <claudiu.manoil@....com>, <vladimir.oltean@....com>,
	<xiaoning.wang@....com>, <andrew+netdev@...n.ch>, <davem@...emloft.net>,
	<edumazet@...gle.com>, <kuba@...nel.org>, <pabeni@...hat.com>,
	<frank.li@....com>, <horms@...nel.org>, <idosch@...sch.org>,
	<netdev@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<imx@...ts.linux.dev>
Subject: Re: [PATCH v8 net-next 1/4] net: enetc: add Tx checksum offload for
 i.MX95 ENETC

From: Wei Fang <wei.fang@....com>
Date: Fri, 13 Dec 2024 10:17:28 +0800

> 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.
> 
> 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.

[...]

> @@ -163,6 +184,30 @@ 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) {
> +			temp_bd.l3_aux0 = FIELD_PREP(ENETC_TX_BD_L3_START,
> +						     skb_network_offset(skb));
> +			temp_bd.l3_aux1 = FIELD_PREP(ENETC_TX_BD_L3_HDR_LEN,
> +						     skb_network_header_len(skb) / 4);
> +			temp_bd.l3_aux1 |= FIELD_PREP(ENETC_TX_BD_L3T,
> +						      enetc_skb_is_ipv6(skb));
> +			if (enetc_skb_is_tcp(skb))
> +				temp_bd.l4_aux = FIELD_PREP(ENETC_TX_BD_L4T,
> +							    ENETC_TXBD_L4T_TCP);
> +			else
> +				temp_bd.l4_aux = FIELD_PREP(ENETC_TX_BD_L4T,
> +							    ENETC_TXBD_L4T_UDP);
> +			flags |= ENETC_TXBD_FLAGS_CSUM_LSO | ENETC_TXBD_FLAGS_L4CS;
> +		} else {
> +			if (skb_checksum_help(skb))

Why not

		} else if (skb_checksum_help(skb)) {

?

> +				return 0;
> +		}
> +	}
> +
>  	i = tx_ring->next_to_use;
>  	txbd = ENETC_TXBD(*tx_ring, i);
>  	prefetchw(txbd);
> @@ -173,7 +218,6 @@ 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;

Why is this removed and how is this change related to the checksum offload?

>  
>  	tx_swbd = &tx_ring->tx_swbd[i];
>  	tx_swbd->dma = dma;
> @@ -594,7 +638,7 @@ static netdev_tx_t enetc_start_xmit(struct sk_buff *skb,
>  {
>  	struct enetc_ndev_priv *priv = netdev_priv(ndev);
>  	struct enetc_bdr *tx_ring;
> -	int count, err;
> +	int count;
>  
>  	/* Queue one-step Sync packet if already locked */
>  	if (skb->cb[0] & ENETC_F_TX_ONESTEP_SYNC_TSTAMP) {
> @@ -627,11 +671,6 @@ static netdev_tx_t enetc_start_xmit(struct sk_buff *skb,
>  			return NETDEV_TX_BUSY;
>  		}
>  
> -		if (skb->ip_summed == CHECKSUM_PARTIAL) {
> -			err = skb_checksum_help(skb);
> -			if (err)
> -				goto drop_packet_err;
> -		}
>  		enetc_lock_mdio();
>  		count = enetc_map_tx_buffs(tx_ring, skb);
>  		enetc_unlock_mdio();
> @@ -3274,6 +3313,7 @@ static const struct enetc_drvdata enetc_pf_data = {
>  
>  static const struct enetc_drvdata enetc4_pf_data = {
>  	.sysclk_freq = ENETC_CLK_333M,
> +	.tx_csum = 1,

Maybe make it `bool tx_csum:1` instead of u8 and assign `true` here?

>  	.pmac_offset = ENETC4_PMAC_OFFSET,
>  	.eth_ops = &enetc4_pf_ethtool_ops,
>  };
> diff --git a/drivers/net/ethernet/freescale/enetc/enetc.h b/drivers/net/ethernet/freescale/enetc/enetc.h
> index 72fa03dbc2dd..e82eb9a9137c 100644
> --- a/drivers/net/ethernet/freescale/enetc/enetc.h
> +++ b/drivers/net/ethernet/freescale/enetc/enetc.h
> @@ -234,6 +234,7 @@ enum enetc_errata {
>  
>  struct enetc_drvdata {
>  	u32 pmac_offset; /* Only valid for PSI which supports 802.1Qbu */
> +	u8 tx_csum:1;
>  	u64 sysclk_freq;
>  	const struct ethtool_ops *eth_ops;
>  };

Thanks,
Olek