net: dsa: b53: Support prepended Broadcom tags

On BCM58xx devices (Northstar Plus), there is an accelerator attached to
port 8 which would only work if we use prepended Broadcom tags. Resolve
that difference in our get_tag_protocol() function by setting the
appropriate tagging protocol in that case. We need to change
b53_brcm_hdr_setup() a little bit now since we can deal with two types
of Broadcom tags.

Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/dsa/b53/Kconfig

@@ -2,6 +2,7 @@ menuconfig B53
 	tristate "Broadcom BCM53xx managed switch support"
 	depends on NET_DSA
 	select NET_DSA_TAG_BRCM
+	select NET_DSA_TAG_BRCM_PREPEND
 	help
 	  This driver adds support for Broadcom managed switch chips. It supports
 	  BCM5325E, BCM5365, BCM539x, BCM53115 and BCM53125 as well as BCM63XX

drivers/net/dsa/b53/b53_common.c

@@ -541,8 +541,8 @@ EXPORT_SYMBOL(b53_disable_port);
 
 void b53_brcm_hdr_setup(struct dsa_switch *ds, int port)
 {
-	bool tag_en = !!(ds->ops->get_tag_protocol(ds, port) ==
+	bool tag_en = !(ds->ops->get_tag_protocol(ds, port) ==
-			 DSA_TAG_PROTO_BRCM);
+			 DSA_TAG_PROTO_NONE);
 	struct b53_device *dev = ds->priv;
 	u8 hdr_ctl, val;
 	u16 reg;
@@ -1505,7 +1505,13 @@ static enum dsa_tag_protocol b53_get_tag_protocol(struct dsa_switch *ds,
 	 */
 	if (is5325(dev) || is5365(dev) || !b53_can_enable_brcm_tags(ds, port))
 		return DSA_TAG_PROTO_NONE;
-	else
+
+	/* Broadcom BCM58xx chips have a flow accelerator on Port 8
+	 * which requires us to use the prepended Broadcom tag type
+	 */
+	if (dev->chip_id == BCM58XX_DEVICE_ID && port == B53_CPU_PORT)
+		return DSA_TAG_PROTO_BRCM_PREPEND;
+
 	return DSA_TAG_PROTO_BRCM;
 }