netdev - [PATCH] enc28j60: Fix sporadic packet loss

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Message-ID: <20081202125046.GD24490@diamond.tkos.co.il>
Date:	Tue, 2 Dec 2008 14:50:46 +0200
From:	Baruch Siach <baruch@...s.co.il>
To:	Claudio Lanconelli <lanconelli.claudio@...ar.com>
Cc:	Shachar Shemesh <shachar@...gnu.com>, netdev@...r.kernel.org
Subject: [PATCH] enc28j60: Fix sporadic packet loss

Packet data read from the RX buffer the when the RSV is at the end of the RX 
buffer does not warp around. This causes packet loss, as the actual data is 
never read. Fix this by calculating the right packet data location.

Thanks to Shachar Shemesh for suggesting the fix.

Signed-off-by: Baruch Siach <baruch@...s.co.il>

---

--- drivers/net/enc28j60.c-git	2008-12-02 14:30:10.000000000 +0200
+++ drivers/net/enc28j60.c	2008-12-02 14:41:51.000000000 +0200
@@ -568,6 +568,17 @@ static u16 erxrdpt_workaround(u16 next_p
 	return erxrdpt;
 }
 
+/*
+ * Calculate wrap arround when reading beyond the end of the RX buffer
+ */
+static u16 rx_packet_start(u16 ptr)
+{
+	if (ptr + RSV_SIZE > RXEND_INIT)
+		return (ptr + RSV_SIZE) - (RXEND_INIT - RXSTART_INIT + 1);
+	else
+		return ptr;
+}
+
 static void nolock_rxfifo_init(struct enc28j60_net *priv, u16 start, u16 end)
 {
 	u16 erxrdpt;
@@ -938,8 +949,9 @@ static void enc28j60_hw_rx(struct net_de
 			skb->dev = ndev;
 			skb_reserve(skb, NET_IP_ALIGN);
 			/* copy the packet from the receive buffer */
-			enc28j60_mem_read(priv, priv->next_pk_ptr + sizeof(rsv),
-					len, skb_put(skb, len));
+			enc28j60_mem_read(priv,
+				rx_packet_start(priv->next_pk_ptr),
+				len, skb_put(skb, len));
 			if (netif_msg_pktdata(priv))
 				dump_packet(__func__, skb->len, skb->data);
 			skb->protocol = eth_type_trans(skb, ndev);

-- 
                                                     ~. .~   Tk Open Systems
=}------------------------------------------------ooO--U--Ooo------------{=
   - baruch@...s.co.il - tel: +972.2.679.5364, http://www.tkos.co.il -
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