r8152: fix the rx early size of RTL8153

revert commit a59e6d8 ("r8152: correct the rx early size") and
fix the rx early size as

	(rx buffer size - rx packet size - rx desc size - alignment) / 4

Signed-off-by: Hayes Wang <[email protected]>
Signed-off-by: David S. Miller <[email protected]>

Author: hayesorz

drivers/net/usb/r8152.c

@@ -32,7 +32,7 @@
 #define NETNEXT_VERSION		"08"
 
 /* Information for net */
-#define NET_VERSION		"8"
+#define NET_VERSION		"9"
 
 #define DRIVER_VERSION		"v1." NETNEXT_VERSION "." NET_VERSION
 #define DRIVER_AUTHOR "Realtek linux nic maintainers <[email protected]>"
@@ -501,6 +501,8 @@ enum rtl_register_content {
 #define RTL8153_RMS		RTL8153_MAX_PACKET
 #define RTL8152_TX_TIMEOUT	(5 * HZ)
 #define RTL8152_NAPI_WEIGHT	64
+#define rx_reserved_size(x)	((x) + VLAN_ETH_HLEN + CRC_SIZE + \
+				 sizeof(struct rx_desc) + RX_ALIGN)
 
 /* rtl8152 flags */
 enum rtl8152_flags {
@@ -2253,8 +2255,7 @@ static void r8153_set_rx_early_timeout(struct r8152 *tp)
 
 static void r8153_set_rx_early_size(struct r8152 *tp)
 {
-	u32 mtu = tp->netdev->mtu;
-	u32 ocp_data = (agg_buf_sz - mtu - VLAN_ETH_HLEN - VLAN_HLEN) / 8;
+	u32 ocp_data = (agg_buf_sz - rx_reserved_size(tp->netdev->mtu)) / 4;
 
 	ocp_write_word(tp, MCU_TYPE_USB, USB_RX_EARLY_SIZE, ocp_data);
 }