r8152: set the RMS of RTL8153 according to the mtu

Set the received maximum size (RMS) according to the mtu size. It is
unnecessary to receive a packet which is more than the size we could
transmit. Besides, this could let the rx buffer be used effectively.
Signed-off-by: Hayes Wang <hayeswang@realtek.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/usb/r8152.c

@@ -2899,7 +2899,8 @@ static void r8153_first_init(struct r8152 *tp)
 
 	rtl_rx_vlan_en(tp, tp->netdev->features & NETIF_F_HW_VLAN_CTAG_RX);
 
-	ocp_write_word(tp, MCU_TYPE_PLA, PLA_RMS, RTL8153_RMS);
+	ocp_data = tp->netdev->mtu + VLAN_ETH_HLEN + CRC_SIZE;
+	ocp_write_word(tp, MCU_TYPE_PLA, PLA_RMS, ocp_data);
 	ocp_write_byte(tp, MCU_TYPE_PLA, PLA_MTPS, MTPS_JUMBO);
 
 	ocp_data = ocp_read_word(tp, MCU_TYPE_PLA, PLA_TCR0);
@@ -2951,7 +2952,8 @@ static void r8153_enter_oob(struct r8152 *tp)
 		usleep_range(1000, 2000);
 	}
 
-	ocp_write_word(tp, MCU_TYPE_PLA, PLA_RMS, RTL8153_RMS);
+	ocp_data = tp->netdev->mtu + VLAN_ETH_HLEN + CRC_SIZE;
+	ocp_write_word(tp, MCU_TYPE_PLA, PLA_RMS, ocp_data);
 
 	ocp_data = ocp_read_word(tp, MCU_TYPE_PLA, PLA_TEREDO_CFG);
 	ocp_data &= ~TEREDO_WAKE_MASK;
@@ -4201,8 +4203,14 @@ static int rtl8152_change_mtu(struct net_device *dev, int new_mtu)
 
 	dev->mtu = new_mtu;
 
-	if (netif_running(dev) && netif_carrier_ok(dev))
-		r8153_set_rx_early_size(tp);
+	if (netif_running(dev)) {
+		u32 rms = new_mtu + VLAN_ETH_HLEN + CRC_SIZE;
+
+		ocp_write_word(tp, MCU_TYPE_PLA, PLA_RMS, rms);
+
+		if (netif_carrier_ok(dev))
+			r8153_set_rx_early_size(tp);
+	}
 
 	mutex_unlock(&tp->control);