diff mbox series

[5.10.y-cip,04/11] net: ravb: Disable IP header RX checksum offloading

Message ID 20250227145720.229324-5-paul.barker.ct@bp.renesas.com (mailing list archive)
State New
Headers show
Series ravb backports: MTU fix, VLAN & IPv6 support | expand

Commit Message

Paul Barker Feb. 27, 2025, 2:57 p.m. UTC 
commit c4e347a02b14fa2425337473fcb120c62936cbc5 upstream.

For IPv4 packets, the header checksum will always be checked in software
in the RX path (inet_gro_receive() calls ip_fast_csum() unconditionally)
so there is no advantage in asking the hardware to also calculate this
checksum.

Reviewed-by: Sergey Shtylyov <s.shtylyov@omp.ru>
Signed-off-by: Paul Barker <paul.barker.ct@bp.renesas.com>
Signed-off-by: Andrew Lunn <andrew@lunn.ch>
[Modified to apply to linux-5.10.y-cip which lacks skb fragment handling
 as we've chosen not to backport 966726324b7b ("net: ravb: Allocate RX
 buffers via page pool")]
Signed-off-by: Paul Barker <paul.barker.ct@bp.renesas.com>
---
 drivers/net/ethernet/renesas/ravb.h      |  2 +-
 drivers/net/ethernet/renesas/ravb_main.c | 15 +++++++++------
 2 files changed, 10 insertions(+), 7 deletions(-)
diff mbox series

Patch

diff --git a/drivers/net/ethernet/renesas/ravb.h b/drivers/net/ethernet/renesas/ravb.h
index 93d8499429cc..03961b10771f 100644
--- a/drivers/net/ethernet/renesas/ravb.h
+++ b/drivers/net/ethernet/renesas/ravb.h
@@ -1012,7 +1012,7 @@  enum CSR2_BIT {
 	CSR2_RDHD	= 0x08000000,
 };
 
-#define CSR2_CSUM_ENABLE (CSR2_RIP4 | CSR2_RTCP4 | CSR2_RUDP4 | CSR2_RICMP4)
+#define CSR2_CSUM_ENABLE (CSR2_RTCP4 | CSR2_RUDP4 | CSR2_RICMP4)
 
 #define DBAT_ENTRY_NUM	22
 #define RX_QUEUE_OFFSET	4
diff --git a/drivers/net/ethernet/renesas/ravb_main.c b/drivers/net/ethernet/renesas/ravb_main.c
index f0b73b8dfb19..c0462fa633c8 100644
--- a/drivers/net/ethernet/renesas/ravb_main.c
+++ b/drivers/net/ethernet/renesas/ravb_main.c
@@ -711,12 +711,17 @@  static void ravb_get_tx_tstamp(struct net_device *ndev)
 
 static void ravb_rx_csum_gbeth(struct sk_buff *skb)
 {
-	__wsum csum_ip_hdr, csum_proto;
+	__wsum csum_proto;
 	u8 *hw_csum;
 
 	/* The hardware checksum status is contained in sizeof(__sum16) * 2 = 4
-	 * bytes appended to packet data. First 2 bytes is ip header checksum
-	 * and last 2 bytes is protocol checksum.
+	 * bytes appended to packet data.
+	 *
+	 * For ipv4, the first 2 bytes are the ip header checksum status. We can
+	 * ignore this as it will always be re-checked in inet_gro_receive().
+	 *
+	 * The last 2 bytes are the protocol checksum status which will be zero
+	 * if the checksum has been validated.
 	 */
 	if (unlikely(skb->len < sizeof(__sum16) * 2))
 		return;
@@ -724,12 +729,10 @@  static void ravb_rx_csum_gbeth(struct sk_buff *skb)
 	hw_csum = skb_tail_pointer(skb) - sizeof(__sum16);
 	csum_proto = csum_unfold((__force __sum16)get_unaligned_le16(hw_csum));
 
-	hw_csum -= sizeof(__sum16);
-	csum_ip_hdr = csum_unfold((__force __sum16)get_unaligned_le16(hw_csum));
 	skb_trim(skb, skb->len - 2 * sizeof(__sum16));
 
 	/* TODO: IPV6 Rx checksum */
-	if (skb->protocol == htons(ETH_P_IP) && !csum_ip_hdr && !csum_proto)
+	if (skb->protocol == htons(ETH_P_IP) && !csum_proto)
 		skb->ip_summed = CHECKSUM_UNNECESSARY;
 }