net: stmmac: Enable dwmac4 jumbo frame more than 8KiB

Enable GMAC v4.xx and beyond to support 16KiB buffer.
Signed-off-by: NWeifeng Voon <weifeng.voon@intel.com>
Signed-off-by: NOng Boon Leong <boon.leong.ong@intel.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/ethernet/stmicro/stmmac/dwmac4_descs.c

@@ -443,6 +443,15 @@ static void dwmac4_clear(struct dma_desc *p)
 	p->des3 = 0;
 }
 
+static int set_16kib_bfsize(int mtu)
+{
+	int ret = 0;
+
+	if (unlikely(mtu >= BUF_SIZE_8KiB))
+		ret = BUF_SIZE_16KiB;
+	return ret;
+}
+
 const struct stmmac_desc_ops dwmac4_desc_ops = {
 	.tx_status = dwmac4_wrback_get_tx_status,
 	.rx_status = dwmac4_wrback_get_rx_status,
@@ -469,4 +478,6 @@ const struct stmmac_desc_ops dwmac4_desc_ops = {
 	.clear = dwmac4_clear,
 };
 
-const struct stmmac_mode_ops dwmac4_ring_mode_ops = { };
+const struct stmmac_mode_ops dwmac4_ring_mode_ops = {
+	.set_16kib_bfsize = set_16kib_bfsize,
+};