From: Vladimir Oltean <vladimir.olt...@nxp.com>

In VLAN-unaware mode, sja1105 uses VLAN tags with a custom TPID of
0xdadb. While in the yet-to-be introduced best_effort_vlan_filtering
mode, it needs to work with normal VLAN TPID values.

A complication arises when we must transmit a VLAN-tagged packet to the
switch when it's in VLAN-aware mode. We need to construct a packet with
2 VLAN tags, and the switch will use the outer header for routing and
pop it on egress. But sadly, here the 2 hardware generations don't
behave the same:

- E/T switches won't pop an ETH_P_8021AD tag on egress, it seems
  (packets will remain double-tagged).
- P/Q/R/S switches will drop a packet with 2 ETH_P_8021Q tags (it looks
  like it tries to prevent VLAN hopping).

But looks like the reverse is also true:

- E/T switches have no problem popping the outer tag from packets with
  2 ETH_P_8021Q tags.
- P/Q/R/S will have no problem popping a single tag even if that is
  ETH_P_8021AD.

So it is clear that if we want the hardware to work with dsa_8021q
tagging in VLAN-aware mode, we need to send different TPIDs depending on
revision. Keep that information in priv->info->qinq_tpid.

The per-port tagger structure will hold an xmit_tpid value that depends
not only upon the qinq_tpid, but also upon the VLAN awareness state
itself (in case we must transmit using 0xdadb).

Signed-off-by: Vladimir Oltean <vladimir.olt...@nxp.com>
---
Changes in v2:
None.

 drivers/net/dsa/sja1105/sja1105.h      |  6 ++++++
 drivers/net/dsa/sja1105/sja1105_main.c | 10 ++++++++++
 drivers/net/dsa/sja1105/sja1105_spi.c  |  6 ++++++
 include/linux/dsa/sja1105.h            |  2 ++
 net/dsa/tag_sja1105.c                  | 17 +++++++----------
 5 files changed, 31 insertions(+), 10 deletions(-)

diff --git a/drivers/net/dsa/sja1105/sja1105.h 
b/drivers/net/dsa/sja1105/sja1105.h
index c80f1999c694..a019ffae38f1 100644
--- a/drivers/net/dsa/sja1105/sja1105.h
+++ b/drivers/net/dsa/sja1105/sja1105.h
@@ -87,6 +87,12 @@ struct sja1105_info {
        const struct sja1105_dynamic_table_ops *dyn_ops;
        const struct sja1105_table_ops *static_ops;
        const struct sja1105_regs *regs;
+       /* Both E/T and P/Q/R/S have quirks when it comes to popping the S-Tag
+        * from double-tagged frames. E/T will pop it only when it's equal to
+        * TPID from the General Parameters Table, while P/Q/R/S will only
+        * pop it when it's equal to TPID2.
+        */
+       u16 qinq_tpid;
        int (*reset_cmd)(struct dsa_switch *ds);
        int (*setup_rgmii_delay)(const void *ctx, int port);
        /* Prototypes from include/net/dsa.h */
diff --git a/drivers/net/dsa/sja1105/sja1105_main.c 
b/drivers/net/dsa/sja1105/sja1105_main.c
index 82b424a03658..042ecbbc5572 100644
--- a/drivers/net/dsa/sja1105/sja1105_main.c
+++ b/drivers/net/dsa/sja1105/sja1105_main.c
@@ -2153,6 +2153,15 @@ static int sja1105_vlan_filtering(struct dsa_switch *ds, 
int port, bool enabled)
                tpid2 = ETH_P_SJA1105;
        }
 
+       for (port = 0; port < ds->num_ports; port++) {
+               struct sja1105_port *sp = &priv->ports[port];
+
+               if (enabled)
+                       sp->xmit_tpid = priv->info->qinq_tpid;
+               else
+                       sp->xmit_tpid = ETH_P_SJA1105;
+       }
+
        if (!enabled)
                state = SJA1105_VLAN_UNAWARE;
        else
@@ -2874,6 +2883,7 @@ static int sja1105_probe(struct spi_device *spi)
                        goto out;
                }
                skb_queue_head_init(&sp->xmit_queue);
+               sp->xmit_tpid = ETH_P_SJA1105;
        }
 
        return 0;
diff --git a/drivers/net/dsa/sja1105/sja1105_spi.c 
b/drivers/net/dsa/sja1105/sja1105_spi.c
index 0be75c49e6c3..a0dacae803cc 100644
--- a/drivers/net/dsa/sja1105/sja1105_spi.c
+++ b/drivers/net/dsa/sja1105/sja1105_spi.c
@@ -512,6 +512,7 @@ struct sja1105_info sja1105e_info = {
        .part_no                = SJA1105ET_PART_NO,
        .static_ops             = sja1105e_table_ops,
        .dyn_ops                = sja1105et_dyn_ops,
+       .qinq_tpid              = ETH_P_8021Q,
        .ptp_ts_bits            = 24,
        .ptpegr_ts_bytes        = 4,
        .reset_cmd              = sja1105et_reset_cmd,
@@ -526,6 +527,7 @@ struct sja1105_info sja1105t_info = {
        .part_no                = SJA1105ET_PART_NO,
        .static_ops             = sja1105t_table_ops,
        .dyn_ops                = sja1105et_dyn_ops,
+       .qinq_tpid              = ETH_P_8021Q,
        .ptp_ts_bits            = 24,
        .ptpegr_ts_bytes        = 4,
        .reset_cmd              = sja1105et_reset_cmd,
@@ -540,6 +542,7 @@ struct sja1105_info sja1105p_info = {
        .part_no                = SJA1105P_PART_NO,
        .static_ops             = sja1105p_table_ops,
        .dyn_ops                = sja1105pqrs_dyn_ops,
+       .qinq_tpid              = ETH_P_8021AD,
        .ptp_ts_bits            = 32,
        .ptpegr_ts_bytes        = 8,
        .setup_rgmii_delay      = sja1105pqrs_setup_rgmii_delay,
@@ -555,6 +558,7 @@ struct sja1105_info sja1105q_info = {
        .part_no                = SJA1105Q_PART_NO,
        .static_ops             = sja1105q_table_ops,
        .dyn_ops                = sja1105pqrs_dyn_ops,
+       .qinq_tpid              = ETH_P_8021AD,
        .ptp_ts_bits            = 32,
        .ptpegr_ts_bytes        = 8,
        .setup_rgmii_delay      = sja1105pqrs_setup_rgmii_delay,
@@ -570,6 +574,7 @@ struct sja1105_info sja1105r_info = {
        .part_no                = SJA1105R_PART_NO,
        .static_ops             = sja1105r_table_ops,
        .dyn_ops                = sja1105pqrs_dyn_ops,
+       .qinq_tpid              = ETH_P_8021AD,
        .ptp_ts_bits            = 32,
        .ptpegr_ts_bytes        = 8,
        .setup_rgmii_delay      = sja1105pqrs_setup_rgmii_delay,
@@ -586,6 +591,7 @@ struct sja1105_info sja1105s_info = {
        .static_ops             = sja1105s_table_ops,
        .dyn_ops                = sja1105pqrs_dyn_ops,
        .regs                   = &sja1105pqrs_regs,
+       .qinq_tpid              = ETH_P_8021AD,
        .ptp_ts_bits            = 32,
        .ptpegr_ts_bytes        = 8,
        .setup_rgmii_delay      = sja1105pqrs_setup_rgmii_delay,
diff --git a/include/linux/dsa/sja1105.h b/include/linux/dsa/sja1105.h
index 136481ce3c6f..e47acf0965c5 100644
--- a/include/linux/dsa/sja1105.h
+++ b/include/linux/dsa/sja1105.h
@@ -9,6 +9,7 @@
 
 #include <linux/skbuff.h>
 #include <linux/etherdevice.h>
+#include <linux/dsa/8021q.h>
 #include <net/dsa.h>
 
 #define ETH_P_SJA1105                          ETH_P_DSA_8021Q
@@ -59,6 +60,7 @@ struct sja1105_port {
        struct sja1105_tagger_data *data;
        struct dsa_port *dp;
        bool hwts_tx_en;
+       u16 xmit_tpid;
 };
 
 bool sja1105_can_use_vlan_as_tags(struct dsa_switch *ds);
diff --git a/net/dsa/tag_sja1105.c b/net/dsa/tag_sja1105.c
index 5368cd34bcf4..0a95fdd7bff8 100644
--- a/net/dsa/tag_sja1105.c
+++ b/net/dsa/tag_sja1105.c
@@ -96,6 +96,11 @@ static struct sk_buff *sja1105_defer_xmit(struct 
sja1105_port *sp,
        return NULL;
 }
 
+static u16 sja1105_xmit_tpid(struct sja1105_port *sp)
+{
+       return sp->xmit_tpid;
+}
+
 static struct sk_buff *sja1105_xmit(struct sk_buff *skb,
                                    struct net_device *netdev)
 {
@@ -111,15 +116,7 @@ static struct sk_buff *sja1105_xmit(struct sk_buff *skb,
        if (unlikely(sja1105_is_link_local(skb)))
                return sja1105_defer_xmit(dp->priv, skb);
 
-       /* If we are under a vlan_filtering bridge, IP termination on
-        * switch ports based on 802.1Q tags is simply too brittle to
-        * be passable. So just defer to the dsa_slave_notag_xmit
-        * implementation.
-        */
-       if (dsa_port_is_vlan_filtering(dp))
-               return skb;
-
-       return dsa_8021q_xmit(skb, netdev, ETH_P_SJA1105,
+       return dsa_8021q_xmit(skb, netdev, sja1105_xmit_tpid(dp->priv),
                             ((pcp << VLAN_PRIO_SHIFT) | tx_vid));
 }
 
@@ -258,7 +255,7 @@ static struct sk_buff *sja1105_rcv(struct sk_buff *skb,
 
        hdr = eth_hdr(skb);
        tpid = ntohs(hdr->h_proto);
-       is_tagged = (tpid == ETH_P_SJA1105);
+       is_tagged = (tpid == ETH_P_SJA1105 || tpid == ETH_P_8021Q);
        is_link_local = sja1105_is_link_local(skb);
        is_meta = sja1105_is_meta_frame(skb);
 
-- 
2.17.1

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