[PATCH] realtek: fix VLAN 0 tag at egress on port 0

[Arinc UNAL (Xeront)]

There is a bug on the ethernet driver where the checks for the DSA tag and
creating the tx header don't include port 0. This causes any frame
egressing from the first port of the switch to have a VLAN 0 tag.

Fix this by extending the checks to include port 0.

Signed-off-by: Arınç ÜNAL <arinc.unal at xeront.com>
---
 .../realtek/files-5.10/drivers/net/ethernet/rtl838x_eth.c   | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/target/linux/realtek/files-5.10/drivers/net/ethernet/rtl838x_eth.c b/target/linux/realtek/files-5.10/drivers/net/ethernet/rtl838x_eth.c
index cf6aabc614..88a27e78ab 100644
--- a/target/linux/realtek/files-5.10/drivers/net/ethernet/rtl838x_eth.c
+++ b/target/linux/realtek/files-5.10/drivers/net/ethernet/rtl838x_eth.c
@@ -96,7 +96,7 @@ static void rtl838x_create_tx_header(struct p_hdr *h, int dest_port, int prio)
 {
 	prio &= 0x7;
 
-	if (dest_port > 0) {
+	if (dest_port >= 0) {
 		// cpu_tag[0] is reserved on the RTL83XX SoCs
 		h->cpu_tag[1] = 0x0401;  // BIT 10: RTL8380_CPU_TAG, BIT0: L2LEARNING on
 		h->cpu_tag[2] = 0x0200;  // Set only AS_DPM, to enable DPM settings below
@@ -113,7 +113,7 @@ static void rtl839x_create_tx_header(struct p_hdr *h, int dest_port, int prio)
 {
 	prio &= 0x7;
 
-	if (dest_port > 0) {
+	if (dest_port >= 0) {
 		// cpu_tag[0] is reserved on the RTL83XX SoCs
 		h->cpu_tag[1] = 0x0100; // RTL8390_CPU_TAG marker
 		h->cpu_tag[2] = h->cpu_tag[3] = h->cpu_tag[4] = h->cpu_tag[5] = 0;
@@ -1142,7 +1142,7 @@ static int rtl838x_eth_tx(struct sk_buff *skb, struct net_device *dev)
 	len = skb->len;
 
 	/* Check for DSA tagging at the end of the buffer */
-	if (netdev_uses_dsa(dev) && skb->data[len-4] == 0x80 && skb->data[len-3] > 0
+	if (netdev_uses_dsa(dev) && skb->data[len-4] == 0x80 && skb->data[len-3] >= 0
 			&& skb->data[len-3] < priv->cpu_port &&  skb->data[len-2] == 0x10
 			&&  skb->data[len-1] == 0x00) {
 		/* Reuse tag space for CRC if possible */
-- 
2.25.1