From: Zumeng Chen <zumeng.chen@xxxxxxxxx> [ Upstream commit 58117672943734715bbe7565ac9f062effa524f0 ] According to LS1021A RM, the value of PAL can be set so that the start of the IP header in the receive data buffer is aligned to a 32-bit boundary. Normally, setting PAL = 2 provides minimal padding to ensure such alignment of the IP header. However every incoming packet's 8-byte time stamp will be inserted into the packet data buffer as padding alignment bytes when hardware time stamping is enabled. So we set the padding 8+2 here to avoid the flooded alignment faults: root@128:~# cat /proc/cpu/alignment User: 0 System: 17539 (inet_gro_receive+0x114/0x2c0) Skipped: 0 Half: 0 Word: 0 DWord: 0 Multi: 17539 User faults: 2 (fixup) Also shown when exception report enablement CPU: 0 PID: 161 Comm: irq/66-eth1_g0_ Not tainted 4.1.21-rt13-WR8.0.0.0_preempt-rt #16 Hardware name: Freescale LS1021A [<8001b420>] (unwind_backtrace) from [<8001476c>] (show_stack+0x20/0x24) [<8001476c>] (show_stack) from [<807cfb48>] (dump_stack+0x94/0xac) [<807cfb48>] (dump_stack) from [<80025d70>] (do_alignment+0x720/0x958) [<80025d70>] (do_alignment) from [<80009224>] (do_DataAbort+0x40/0xbc) [<80009224>] (do_DataAbort) from [<80015398>] (__dabt_svc+0x38/0x60) Exception stack(0x86ad1cc0 to 0x86ad1d08) 1cc0: f9b3e080 86b3d072 2d78d287 00000000 866816c0 86b3d05e 86e785d0 00000000 1ce0: 00000011 0000000e 80840ab0 86ad1d3c 86ad1d08 86ad1d08 806d7fc0 806d806c 1d00: 40070013 ffffffff [<80015398>] (__dabt_svc) from [<806d806c>] (inet_gro_receive+0x114/0x2c0) [<806d806c>] (inet_gro_receive) from [<80660eec>] (dev_gro_receive+0x21c/0x3c0) [<80660eec>] (dev_gro_receive) from [<8066133c>] (napi_gro_receive+0x44/0x17c) [<8066133c>] (napi_gro_receive) from [<804f0538>] (gfar_clean_rx_ring+0x39c/0x7d4) [<804f0538>] (gfar_clean_rx_ring) from [<804f0bf4>] (gfar_poll_rx_sq+0x58/0xe0) [<804f0bf4>] (gfar_poll_rx_sq) from [<80660b10>] (net_rx_action+0x27c/0x43c) [<80660b10>] (net_rx_action) from [<80033638>] (do_current_softirqs+0x1e0/0x3dc) [<80033638>] (do_current_softirqs) from [<800338c4>] (__local_bh_enable+0x90/0xa8) [<800338c4>] (__local_bh_enable) from [<8008025c>] (irq_forced_thread_fn+0x70/0x84) [<8008025c>] (irq_forced_thread_fn) from [<800805e8>] (irq_thread+0x16c/0x244) [<800805e8>] (irq_thread) from [<8004e490>] (kthread+0xe8/0x104) [<8004e490>] (kthread) from [<8000fda8>] (ret_from_fork+0x14/0x2c) Signed-off-by: Zumeng Chen <zumeng.chen@xxxxxxxxx> Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx> Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxxxx> --- drivers/net/ethernet/freescale/gianfar.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/drivers/net/ethernet/freescale/gianfar.c b/drivers/net/ethernet/freescale/gianfar.c index 7923bfdc9b30..901661149b44 100644 --- a/drivers/net/ethernet/freescale/gianfar.c +++ b/drivers/net/ethernet/freescale/gianfar.c @@ -1375,9 +1375,11 @@ static int gfar_probe(struct platform_device *ofdev) gfar_init_addr_hash_table(priv); - /* Insert receive time stamps into padding alignment bytes */ + /* Insert receive time stamps into padding alignment bytes, and + * plus 2 bytes padding to ensure the cpu alignment. + */ if (priv->device_flags & FSL_GIANFAR_DEV_HAS_TIMER) - priv->padding = 8; + priv->padding = 8 + DEFAULT_PADDING; if (dev->features & NETIF_F_IP_CSUM || priv->device_flags & FSL_GIANFAR_DEV_HAS_TIMER) -- 2.11.0