Merge branch 'macb-TSO-bug-fixes'

Harini Katakam says:

====================
macb: TSO bug fixes

An IP errata was recently discovered when testing TSO enabled versions
with perf test tools where a false amba error is reported by the IP.
Some ways to reproduce would be to use iperf or applications with payload
descriptor sizes very close to 16K. Once the error is observed TXERR (or
bit 6 of ISR) will be constantly triggered leading to a series of tx path
error handling and clean up. Workaround the same by limiting this size to
0x3FC0 as recommended by Cadence. There was no performance impact on 1G
system that I tested with.

Note on patch 1: The alignment code may be unused but leaving it there
in case anyone is using UFO.

Added Fixes tag to patch 1.
====================
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/cadence/macb_main.c

@@ -73,7 +73,11 @@ struct sifive_fu540_macb_mgmt {
 /* Max length of transmit frame must be a multiple of 8 bytes */
 #define MACB_TX_LEN_ALIGN	8
 #define MACB_MAX_TX_LEN		((unsigned int)((1 << MACB_TX_FRMLEN_SIZE) - 1) & ~((unsigned int)(MACB_TX_LEN_ALIGN - 1)))
-#define GEM_MAX_TX_LEN		((unsigned int)((1 << GEM_TX_FRMLEN_SIZE) - 1) & ~((unsigned int)(MACB_TX_LEN_ALIGN - 1)))
+/* Limit maximum TX length as per Cadence TSO errata. This is to avoid a
+ * false amba_error in TX path from the DMA assuming there is not enough
+ * space in the SRAM (16KB) even when there is.
+ */
+#define GEM_MAX_TX_LEN		(unsigned int)(0x3FC0)
 
 #define GEM_MTU_MIN_SIZE	ETH_MIN_MTU
 #define MACB_NETIF_LSO		NETIF_F_TSO
@@ -1791,16 +1795,14 @@ static netdev_features_t macb_features_check(struct sk_buff *skb,
 
 	/* Validate LSO compatibility */
 
-	/* there is only one buffer */
-	if (!skb_is_nonlinear(skb))
+	/* there is only one buffer or protocol is not UDP */
+	if (!skb_is_nonlinear(skb) || (ip_hdr(skb)->protocol != IPPROTO_UDP))
 		return features;
 
 	/* length of header */
 	hdrlen = skb_transport_offset(skb);
-	if (ip_hdr(skb)->protocol == IPPROTO_TCP)
-		hdrlen += tcp_hdrlen(skb);
 
-	/* For LSO:
+	/* For UFO only:
 	 * When software supplies two or more payload buffers all payload buffers
 	 * apart from the last must be a multiple of 8 bytes in size.
 	 */