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Commit 3ac72b7b authored by Eric Nelson's avatar Eric Nelson Committed by David S. Miller
Browse files

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: default avatarEric Nelson <eric@nelint.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 97dc499c

drivers/net/ethernet/freescale/fec_main.c

+10 −1
Original line number Diff line number Diff line
@@ -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);