stmmac: allow mtu bigger than 1500 in case of normal desc (V4)

This patch allows to set the mtu bigger than 1500
in case of normal descriptors.
This is helping some SPEAr customers.

Signed-off-by: Deepak SIKRI <deepak.sikri@st.com>
Signed-off-by: Giuseppe Cavallaro <peppe.cavallaro@st.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/stmicro/stmmac/norm_desc.c

@@ -126,6 +126,7 @@ static void ndesc_init_rx_desc(struct dma_desc *p, unsigned int ring_size,
 	for (i = 0; i < ring_size; i++) {
 		p->des01.rx.own = 1;
 		p->des01.rx.buffer1_size = BUF_SIZE_2KiB - 1;
+		p->des01.rx.buffer2_size = BUF_SIZE_2KiB - 1;
 		if (i == ring_size - 1)
 			p->des01.rx.end_ring = 1;
 		if (disable_rx_ic)
@@ -183,7 +184,12 @@ static void ndesc_prepare_tx_desc(struct dma_desc *p, int is_fs, int len,
 				  int csum_flag)
 {
 	p->des01.tx.first_segment = is_fs;
-	p->des01.tx.buffer1_size = len;
+
+	if (unlikely(len > BUF_SIZE_2KiB)) {
+		p->des01.etx.buffer1_size = BUF_SIZE_2KiB - 1;
+		p->des01.etx.buffer2_size = len - p->des01.etx.buffer1_size;
+	} else
+		p->des01.tx.buffer1_size = len;
 }
 
 static void ndesc_clear_tx_ic(struct dma_desc *p)

drivers/net/ethernet/stmicro/stmmac/stmmac_main.c

@@ -1412,10 +1412,10 @@ static int stmmac_change_mtu(struct net_device *dev, int new_mtu)
 		return -EBUSY;
 	}
 
-	if (priv->plat->has_gmac)
+	if (priv->plat->enh_desc)
 		max_mtu = JUMBO_LEN;
 	else
-		max_mtu = ETH_DATA_LEN;
+		max_mtu = BUF_SIZE_4KiB;
 
 	if ((new_mtu < 46) || (new_mtu > max_mtu)) {
 		pr_err("%s: invalid MTU, max MTU is: %d\n", dev->name, max_mtu);