netdev - Backported alx driver fix for stable 4.4 kernel and older

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Date:	Tue, 28 Jun 2016 16:23:44 +0800
From:	Feng Tang <feng.tang@...el.com>
To:	"David S. Miller" <davem@...emloft.net>
Cc:	Eric Dumazet <edumazet@...gle.com>, Ole Lukoie <olelukoie@...l.ru>,
	netdev@...r.kernel.org
Subject: Backported alx driver fix for stable 4.4 kernel and older

Hi David,

Greg KH has picked up the alx driver fix for 4.6 stable kernel, and
people are asking about plan for 4.4/4.1 stable kernel in
	https://bugzilla.kernel.org/show_bug.cgi?id=70761

Since the fix patch in your "net" git can't be applied to 4.4 and older
kernel as is, so I backport it as follows. Could you help to add it
to your stable queue.

Let me know if I break any netdev+stable patch rule, thanks

- Feng

----

>From 9c9caee22400c7ed3a514b1ee5e017e5e5b6b812 Mon Sep 17 00:00:00 2001
From: Feng Tang <feng.tang@...el.com>
Date: Fri, 24 Jun 2016 15:26:05 +0800
Subject: [PATCH] net: alx: Work around the DMA RX overflow issue

Note: This is a verified backported patch for stable 4.4 kernel, and it
could also be applied to 4.3/4.2/4.1/3.18/3.16

There is a problem with alx devices, that the network link will be
lost in 1-5 minutes after the device is up.

>From debugging without datasheet, we found the error always
happen when the DMA RX address is set to 0x....fc0, which is very
likely to be a HW/silicon problem.

This patch will apply rx skb with 64 bytes longer space, and if the
allocated skb has a 0x...fc0 address, it will use skb_resever(skb, 64)
to advance the address, so that the RX overflow can be avoided.

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=70761
Signed-off-by: Feng Tang <feng.tang@...el.com>
Suggested-by: Eric Dumazet <edumazet@...gle.com>
Tested-by: Ole Lukoie <olelukoie@...l.ru>
---
 drivers/net/ethernet/atheros/alx/main.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/atheros/alx/main.c b/drivers/net/ethernet/atheros/alx/main.c
index c8af3ce..a43d6a8 100644
--- a/drivers/net/ethernet/atheros/alx/main.c
+++ b/drivers/net/ethernet/atheros/alx/main.c
@@ -86,9 +86,14 @@ static int alx_refill_rx_ring(struct alx_priv *alx, gfp_t gfp)
 	while (!cur_buf->skb && next != rxq->read_idx) {
 		struct alx_rfd *rfd = &rxq->rfd[cur];
 
-		skb = __netdev_alloc_skb(alx->dev, alx->rxbuf_size, gfp);
+		skb = __netdev_alloc_skb(alx->dev, alx->rxbuf_size + 64, gfp);
 		if (!skb)
 			break;
+
+		/* Workround for the HW RX DMA overflow issue */
+		if (((unsigned long)skb->data & 0xfff) == 0xfc0)
+			skb_reserve(skb, 64);
+
 		dma = dma_map_single(&alx->hw.pdev->dev,
 				     skb->data, alx->rxbuf_size,
 				     DMA_FROM_DEVICE);
-- 
2.5.0


View attachment "0001-net-alx-Work-around-the-DMA-RX-overflow-issue.patch" of type "text/x-diff" (1917 bytes)