From 3ac72b7b63d57b231dda1e8f8d13872e0d7e8603 Mon Sep 17 00:00:00 2001 From: Eric Nelson Date: Sat, 24 Sep 2016 07:42:19 -0700 Subject: [PATCH] net: fec: align IP header in hardware The FEC receive accelerator (RACC) supports shifting the data payload of received packets by 16-bits, which aligns the payload (IP header) on a 4-byte boundary, which is, if not required, at least strongly suggested by the Linux networking layer. Without this patch, a huge number of alignment faults will be taken by the IP stack, as seen in /proc/cpu/alignment: ~/$ cat /proc/cpu/alignment User: 0 System: 72645 (inet_gro_receive+0x104/0x27c) Skipped: 0 Half: 0 Word: 0 DWord: 0 Multi: 72645 User faults: 3 (fixup+warn) This patch was suggested by Andrew Lunn in this message to linux-netdev: http://marc.info/?l=linux-arm-kernel&m=147465452108384&w=2 and adapted from a patch by Russell King from 2014: http://git.arm.linux.org.uk/cgit/linux-arm.git/commit/?id=70d8a8a Signed-off-by: Eric Nelson Signed-off-by: David S. Miller --- drivers/net/ethernet/freescale/fec_main.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) diff --git a/drivers/net/ethernet/freescale/fec_main.c b/drivers/net/ethernet/freescale/fec_main.c index 3fb11f929adc..692ee248e486 100644 --- a/drivers/net/ethernet/freescale/fec_main.c +++ b/drivers/net/ethernet/freescale/fec_main.c @@ -180,6 +180,7 @@ MODULE_PARM_DESC(macaddr, "FEC Ethernet MAC address"); /* FEC receive acceleration */ #define FEC_RACC_IPDIS (1 << 1) #define FEC_RACC_PRODIS (1 << 2) +#define FEC_RACC_SHIFT16 BIT(7) #define FEC_RACC_OPTIONS (FEC_RACC_IPDIS | FEC_RACC_PRODIS) /* @@ -945,9 +946,11 @@ fec_restart(struct net_device *ndev) #if !defined(CONFIG_M5272) if (fep->quirks & FEC_QUIRK_HAS_RACC) { - /* set RX checksum */ val = readl(fep->hwp + FEC_RACC); + /* align IP header */ + val |= FEC_RACC_SHIFT16; if (fep->csum_flags & FLAG_RX_CSUM_ENABLED) + /* set RX checksum */ val |= FEC_RACC_OPTIONS; else val &= ~FEC_RACC_OPTIONS; @@ -1428,6 +1431,12 @@ fec_enet_rx_queue(struct net_device *ndev, int budget, u16 queue_id) prefetch(skb->data - NET_IP_ALIGN); skb_put(skb, pkt_len - 4); data = skb->data; + +#if !defined(CONFIG_M5272) + if (fep->quirks & FEC_QUIRK_HAS_RACC) + data = skb_pull_inline(skb, 2); +#endif + if (!is_copybreak && need_swap) swap_buffer(data, pkt_len); -- 2.20.1