sfc: only use fixed-id if the skb asks for it

AIUI, the NETIF_F_TSO_MANGLEID flag is a signal to the stack that a
 driver may _need_ to mangle IDs in order to do TSO, and conversely
 a signal from the stack that the driver is permitted to do so.
Since we support both fixed and incrementing IPIDs, we should rely
 on the SKB_GSO_FIXEDID flag on a per-skb basis, rather than using
 the MANGLEID feature to make all TSOs fixed-id.
Includes other minor cleanups of ef100_make_tso_desc() coding style.
Signed-off-by: Edward Cree <ecree@solarflare.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/sfc/ef100_nic.c

@@ -694,7 +694,7 @@ static unsigned int ef100_check_caps(const struct efx_nic *efx,
 #define EF100_OFFLOAD_FEATURES	(NETIF_F_HW_CSUM | NETIF_F_RXCSUM |	\
 	NETIF_F_HIGHDMA | NETIF_F_SG | NETIF_F_FRAGLIST | NETIF_F_NTUPLE | \
 	NETIF_F_RXHASH | NETIF_F_RXFCS | NETIF_F_TSO_ECN | NETIF_F_RXALL | \
-	NETIF_F_TSO_MANGLEID | NETIF_F_HW_VLAN_CTAG_TX)
+	NETIF_F_HW_VLAN_CTAG_TX)
 
 const struct efx_nic_type ef100_pf_nic_type = {
 	.revision = EFX_REV_EF100,

drivers/net/ethernet/sfc/ef100_tx.c

@@ -187,21 +187,22 @@ static void ef100_make_tso_desc(struct efx_nic *efx,
 				struct efx_tx_buffer *buffer, efx_oword_t *txd,
 				unsigned int segment_count)
 {
-	u32 mangleid = (efx->net_dev->features & NETIF_F_TSO_MANGLEID) ||
-		skb_shinfo(skb)->gso_type & SKB_GSO_TCP_FIXEDID ?
-		ESE_GZ_TX_DESC_IP4_ID_NO_OP :
-		ESE_GZ_TX_DESC_IP4_ID_INC_MOD16;
-	u16 vlan_enable =  efx->net_dev->features & NETIF_F_HW_VLAN_CTAG_TX ?
-		skb_vlan_tag_present(skb) : 0;
 	bool gso_partial = skb_shinfo(skb)->gso_type & SKB_GSO_PARTIAL;
 	unsigned int len, ip_offset, tcp_offset, payload_segs;
+	u32 mangleid = ESE_GZ_TX_DESC_IP4_ID_INC_MOD16;
 	unsigned int outer_ip_offset, outer_l4_offset;
 	u16 vlan_tci = skb_vlan_tag_get(skb);
 	u32 mss = skb_shinfo(skb)->gso_size;
 	bool encap = skb->encapsulation;
+	u16 vlan_enable = 0;
 	struct tcphdr *tcp;
 	u32 paylen;
 
+	if (skb_shinfo(skb)->gso_type & SKB_GSO_TCP_FIXEDID)
+		mangleid = ESE_GZ_TX_DESC_IP4_ID_NO_OP;
+	if (efx->net_dev->features & NETIF_F_HW_VLAN_CTAG_TX)
+		vlan_enable = skb_vlan_tag_present(skb);
+
 	len = skb->len - buffer->len;
 	/* We use 1 for the TSO descriptor and 1 for the header */
 	payload_segs = segment_count - 2;