net: mscc: ocelot: don't use NPI tag prefix for the CPU port module

Context: Ocelot switches put the injection/extraction frame header in
front of the Ethernet header. When used in NPI mode, a DSA master would
see junk instead of the destination MAC address, and it would most
likely drop the packets. So the Ocelot frame header can have an optional
prefix, which is just "ff:ff:ff:ff:ff:fe > ff:ff:ff:ff:ff:ff" padding
put before the actual tag (still before the real Ethernet header) such
that the DSA master thinks it's looking at a broadcast frame with a
strange EtherType.

Unfortunately, a lesson learned in commit 69df578 ("net: mscc:
ocelot: eliminate confusion between CPU and NPI port") seems to have
been forgotten in the meanwhile.

The CPU port module and the NPI port have independent settings for the
length of the tag prefix. However, the driver is using the same variable
to program both of them.

There is no reason really to use any tag prefix with the CPU port
module, since that is not connected to any Ethernet port. So this patch
makes the inj_prefix and xtr_prefix variables apply only to the NPI
port (which the switchdev ocelot_vsc7514 driver does not use).

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/dsa/ocelot/felix.c

@@ -425,8 +425,8 @@ static int felix_init_structs(struct felix *felix, int num_phys_ports)
 	ocelot->num_mact_rows	= felix->info->num_mact_rows;
 	ocelot->vcap		= felix->info->vcap;
 	ocelot->ops		= felix->info->ops;
-	ocelot->inj_prefix	= OCELOT_TAG_PREFIX_SHORT;
-	ocelot->xtr_prefix	= OCELOT_TAG_PREFIX_SHORT;
+	ocelot->npi_inj_prefix	= OCELOT_TAG_PREFIX_SHORT;
+	ocelot->npi_xtr_prefix	= OCELOT_TAG_PREFIX_SHORT;
 	ocelot->devlink		= felix->ds->devlink;
 
 	port_phy_modes = kcalloc(num_phys_ports, sizeof(phy_interface_t),
@@ -541,9 +541,9 @@ static void felix_npi_port_init(struct ocelot *ocelot, int port)
 
 	/* NPI port Injection/Extraction configuration */
 	ocelot_fields_write(ocelot, port, SYS_PORT_MODE_INCL_XTR_HDR,
-			    ocelot->xtr_prefix);
+			    ocelot->npi_xtr_prefix);
 	ocelot_fields_write(ocelot, port, SYS_PORT_MODE_INCL_INJ_HDR,
-			    ocelot->inj_prefix);
+			    ocelot->npi_inj_prefix);
 
 	/* Disable transmission of pause frames */
 	ocelot_fields_write(ocelot, port, SYS_PAUSE_CFG_PAUSE_ENA, 0);

drivers/net/ethernet/mscc/ocelot.c

@@ -1359,9 +1359,9 @@ void ocelot_port_set_maxlen(struct ocelot *ocelot, int port, size_t sdu)
 	if (port == ocelot->npi) {
 		maxlen += OCELOT_TAG_LEN;
 
-		if (ocelot->inj_prefix == OCELOT_TAG_PREFIX_SHORT)
+		if (ocelot->npi_inj_prefix == OCELOT_TAG_PREFIX_SHORT)
 			maxlen += OCELOT_SHORT_PREFIX_LEN;
-		else if (ocelot->inj_prefix == OCELOT_TAG_PREFIX_LONG)
+		else if (ocelot->npi_inj_prefix == OCELOT_TAG_PREFIX_LONG)
 			maxlen += OCELOT_LONG_PREFIX_LEN;
 	}
 
@@ -1391,9 +1391,9 @@ int ocelot_get_max_mtu(struct ocelot *ocelot, int port)
 	if (port == ocelot->npi) {
 		max_mtu -= OCELOT_TAG_LEN;
 
-		if (ocelot->inj_prefix == OCELOT_TAG_PREFIX_SHORT)
+		if (ocelot->npi_inj_prefix == OCELOT_TAG_PREFIX_SHORT)
 			max_mtu -= OCELOT_SHORT_PREFIX_LEN;
-		else if (ocelot->inj_prefix == OCELOT_TAG_PREFIX_LONG)
+		else if (ocelot->npi_inj_prefix == OCELOT_TAG_PREFIX_LONG)
 			max_mtu -= OCELOT_LONG_PREFIX_LEN;
 	}
 
@@ -1478,9 +1478,9 @@ static void ocelot_cpu_port_init(struct ocelot *ocelot)
 	ocelot_fields_write(ocelot, cpu, QSYS_SWITCH_PORT_MODE_PORT_ENA, 1);
 	/* CPU port Injection/Extraction configuration */
 	ocelot_fields_write(ocelot, cpu, SYS_PORT_MODE_INCL_XTR_HDR,
-			    ocelot->xtr_prefix);
+			    OCELOT_TAG_PREFIX_NONE);
 	ocelot_fields_write(ocelot, cpu, SYS_PORT_MODE_INCL_INJ_HDR,
-			    ocelot->inj_prefix);
+			    OCELOT_TAG_PREFIX_NONE);
 
 	/* Configure the CPU port to be VLAN aware */
 	ocelot_write_gix(ocelot, ANA_PORT_VLAN_CFG_VLAN_VID(0) |

drivers/net/ethernet/mscc/ocelot_vsc7514.c

@@ -1347,8 +1347,6 @@ static int mscc_ocelot_probe(struct platform_device *pdev)
 	ocelot->num_flooding_pgids = 1;
 
 	ocelot->vcap = vsc7514_vcap_props;
-	ocelot->inj_prefix = OCELOT_TAG_PREFIX_NONE;
-	ocelot->xtr_prefix = OCELOT_TAG_PREFIX_NONE;
 	ocelot->npi = -1;
 
 	err = ocelot_init(ocelot);

include/soc/mscc/ocelot.h

@@ -651,8 +651,8 @@ struct ocelot {
 
 	int				npi;
 
-	enum ocelot_tag_prefix		inj_prefix;
-	enum ocelot_tag_prefix		xtr_prefix;
+	enum ocelot_tag_prefix		npi_inj_prefix;
+	enum ocelot_tag_prefix		npi_xtr_prefix;
 
 	u32				*lags;