net: dsa: tag_ocelot: use a short prefix on both ingress and egress

There are 2 goals that we follow:

- Reduce the header size
- Make the header size equal between RX and TX

The issue that required long prefix on RX was the fact that the ocelot
DSA tag, being put before Ethernet as it is, would overlap with the area
that a DSA master uses for RX filtering (destination MAC address
mainly).

Now that we can ask DSA to put the master in promiscuous mode, in theory
we could remove the prefix altogether and call it a day, but it looks
like we can't. Using no prefix on ingress, some packets (such as ICMP)
would be received, while others (such as PTP) would not be received.
This is because the DSA master we use (enetc) triggers parse errors
("MAC rx frame errors") presumably because it sees Ethernet frames with
a bad length. And indeed, when using no prefix, the EtherType (bytes
12-13 of the frame, bits 96-111) falls over the REW_VAL field from the
extraction header, aka the PTP timestamp.

When turning the short (32-bit) prefix on, the EtherType overlaps with
bits 64-79 of the extraction header, which are a reserved area
transmitted as zero by the switch. The packets are not dropped by the
DSA master with a short prefix. Actually, the frames look like this in
tcpdump (below is a PTP frame, with an extra dsa_8021q tag - dadb 0482 -
added by a downstream sja1105).

89:0c:a9:f2:01:00 > 88:80:00:0a:00:1d, 802.3, length 0: LLC, \
	dsap Unknown (0x10) Individual, ssap ProWay NM (0x0e) Response, \
	ctrl 0x0004: Information, send seq 2, rcv seq 0, \
	Flags [Response], length 78

0x0000:  8880 000a 001d 890c a9f2 0100 0000 100f  ................
0x0010:  0400 0000 0180 c200 000e 001f 7b63 0248  ............{c.H
0x0020:  dadb 0482 88f7 1202 0036 0000 0000 0000  .........6......
0x0030:  0000 0000 0000 0000 0000 001f 7bff fe63  ............{..c
0x0040:  0248 0001 1f81 0500 0000 0000 0000 0000  .H..............
0x0050:  0000 0000 0000 0000 0000 0000            ............

So the short prefix is our new default: we've shortened our RX frames by
12 octets, increased TX by 4, and headers are now equal between RX and
TX. Note that we still need promiscuous mode for the DSA master to not
drop it.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/dsa/ocelot/felix.c b/drivers/net/dsa/ocelot/felix.c
index b8e192374a329aeecd3056771ffc087e5b37af66..ab3ee5c3fd02e1b39737ed9cf9ba4e0e944abf31 100644 (file)
--- a/drivers/net/dsa/ocelot/felix.c
+++ b/drivers/net/dsa/ocelot/felix.c
@@ -439,8 +439,8 @@ static int felix_init_structs(struct felix *felix, int num_phys_ports)
        ocelot->vcap_is2_actions= felix->info->vcap_is2_actions;
        ocelot->vcap            = felix->info->vcap;
        ocelot->ops             = felix->info->ops;
-       ocelot->inj_prefix      = OCELOT_TAG_PREFIX_NONE;
-       ocelot->xtr_prefix      = OCELOT_TAG_PREFIX_LONG;
+       ocelot->inj_prefix      = OCELOT_TAG_PREFIX_SHORT;
+       ocelot->xtr_prefix      = OCELOT_TAG_PREFIX_SHORT;
 
        port_phy_modes = kcalloc(num_phys_ports, sizeof(phy_interface_t),
                                 GFP_KERNEL);
@@ -511,7 +511,7 @@ static int felix_init_structs(struct felix *felix, int num_phys_ports)
                        return PTR_ERR(target);
                }
 
-               template = devm_kzalloc(ocelot->dev, OCELOT_TAG_LEN,
+               template = devm_kzalloc(ocelot->dev, OCELOT_TOTAL_TAG_LEN,
                                        GFP_KERNEL);
                if (!template) {
                        dev_err(ocelot->dev,

diff --git a/drivers/net/dsa/ocelot/felix_vsc9959.c b/drivers/net/dsa/ocelot/felix_vsc9959.c
index 3ab6d6847c5bbe15b680ce8a46bc78df7b9b90ac..2e9270c00096d94ca58936f2bd28a25f8e35aa85 100644 (file)
--- a/drivers/net/dsa/ocelot/felix_vsc9959.c
+++ b/drivers/net/dsa/ocelot/felix_vsc9959.c
@@ -1155,6 +1155,8 @@ static void vsc9959_xmit_template_populate(struct ocelot *ocelot, int port)
        struct ocelot_port *ocelot_port = ocelot->ports[port];
        u8 *template = ocelot_port->xmit_template;
        u64 bypass, dest, src;
+       __be32 *prefix;
+       u8 *injection;
 
        /* Set the source port as the CPU port module and not the
         * NPI port
@@ -1163,9 +1165,14 @@ static void vsc9959_xmit_template_populate(struct ocelot *ocelot, int port)
        dest = BIT(port);
        bypass = true;
 
-       packing(template, &bypass, 127, 127, OCELOT_TAG_LEN, PACK, 0);
-       packing(template, &dest,    68,  56, OCELOT_TAG_LEN, PACK, 0);
-       packing(template, &src,     46,  43, OCELOT_TAG_LEN, PACK, 0);
+       injection = template + OCELOT_SHORT_PREFIX_LEN;
+       prefix = (__be32 *)template;
+
+       packing(injection, &bypass, 127, 127, OCELOT_TAG_LEN, PACK, 0);
+       packing(injection, &dest,    68,  56, OCELOT_TAG_LEN, PACK, 0);
+       packing(injection, &src,     46,  43, OCELOT_TAG_LEN, PACK, 0);
+
+       *prefix = cpu_to_be32(0x8880000a);
 }
 
 static const struct felix_info felix_info_vsc9959 = {

diff --git a/drivers/net/dsa/ocelot/seville_vsc9953.c b/drivers/net/dsa/ocelot/seville_vsc9953.c
index b0ff90c0ae160b1c357adfd0ae1972ba22742977..e28dd600f4641758a24d89e8b724920c0822207c 100644 (file)
--- a/drivers/net/dsa/ocelot/seville_vsc9953.c
+++ b/drivers/net/dsa/ocelot/seville_vsc9953.c
@@ -1003,6 +1003,8 @@ static void vsc9953_xmit_template_populate(struct ocelot *ocelot, int port)
        struct ocelot_port *ocelot_port = ocelot->ports[port];
        u8 *template = ocelot_port->xmit_template;
        u64 bypass, dest, src;
+       __be32 *prefix;
+       u8 *injection;
 
        /* Set the source port as the CPU port module and not the
         * NPI port
@@ -1011,9 +1013,14 @@ static void vsc9953_xmit_template_populate(struct ocelot *ocelot, int port)
        dest = BIT(port);
        bypass = true;
 
-       packing(template, &bypass, 127, 127, OCELOT_TAG_LEN, PACK, 0);
-       packing(template, &dest,    67,  57, OCELOT_TAG_LEN, PACK, 0);
-       packing(template, &src,     46,  43, OCELOT_TAG_LEN, PACK, 0);
+       injection = template + OCELOT_SHORT_PREFIX_LEN;
+       prefix = (__be32 *)template;
+
+       packing(injection, &bypass, 127, 127, OCELOT_TAG_LEN, PACK, 0);
+       packing(injection, &dest,    67,  57, OCELOT_TAG_LEN, PACK, 0);
+       packing(injection, &src,     46,  43, OCELOT_TAG_LEN, PACK, 0);
+
+       *prefix = cpu_to_be32(0x88800005);
 }
 
 static const struct felix_info seville_info_vsc9953 = {

diff --git a/include/soc/mscc/ocelot.h b/include/soc/mscc/ocelot.h
index 349e839c4c18bc23a77bece8f2a7151fc8ebd0cd..3093385f614779c0b158085e17440889689a8070 100644 (file)
--- a/include/soc/mscc/ocelot.h
+++ b/include/soc/mscc/ocelot.h
@@ -101,6 +101,7 @@
 #define OCELOT_TAG_LEN                 16
 #define OCELOT_SHORT_PREFIX_LEN                4
 #define OCELOT_LONG_PREFIX_LEN         16
+#define OCELOT_TOTAL_TAG_LEN   (OCELOT_SHORT_PREFIX_LEN + OCELOT_TAG_LEN)
 
 #define OCELOT_SPEED_2500              0
 #define OCELOT_SPEED_1000              1

diff --git a/net/dsa/tag_ocelot.c b/net/dsa/tag_ocelot.c
index d1a7e224adff80764dab04e59114549dd7f3f2c2..ec16badb7812676e2fe680db692858cbb58ab3ea 100644 (file)
--- a/net/dsa/tag_ocelot.c
+++ b/net/dsa/tag_ocelot.c
@@ -141,10 +141,12 @@ static struct sk_buff *ocelot_xmit(struct sk_buff *skb,
        struct dsa_switch *ds = dp->ds;
        struct ocelot *ocelot = ds->priv;
        struct ocelot_port *ocelot_port;
+       u8 *prefix, *injection;
        u64 qos_class, rew_op;
-       u8 *injection;
+       int err;
 
-       if (unlikely(skb_cow_head(skb, OCELOT_TAG_LEN) < 0)) {
+       err = skb_cow_head(skb, OCELOT_TOTAL_TAG_LEN);
+       if (unlikely(err < 0)) {
                netdev_err(netdev, "Cannot make room for tag.\n");
                return NULL;
        }
@@ -153,7 +155,10 @@ static struct sk_buff *ocelot_xmit(struct sk_buff *skb,
 
        injection = skb_push(skb, OCELOT_TAG_LEN);
 
-       memcpy(injection, ocelot_port->xmit_template, OCELOT_TAG_LEN);
+       prefix = skb_push(skb, OCELOT_SHORT_PREFIX_LEN);
+
+       memcpy(prefix, ocelot_port->xmit_template, OCELOT_TOTAL_TAG_LEN);
+
        /* Fix up the fields which are not statically determined
         * in the template
         */
@@ -187,11 +192,11 @@ static struct sk_buff *ocelot_rcv(struct sk_buff *skb,
         * so it points to the beginning of the frame.
         */
        skb_push(skb, ETH_HLEN);
-       /* We don't care about the long prefix, it is just for easy entrance
+       /* We don't care about the short prefix, it is just for easy entrance
         * into the DSA master's RX filter. Discard it now by moving it into
         * the headroom.
         */
-       skb_pull(skb, OCELOT_LONG_PREFIX_LEN);
+       skb_pull(skb, OCELOT_SHORT_PREFIX_LEN);
        /* And skb->data now points to the extraction frame header.
         * Keep a pointer to it.
         */
@@ -205,7 +210,7 @@ static struct sk_buff *ocelot_rcv(struct sk_buff *skb,
        skb_pull(skb, ETH_HLEN);
 
        /* Remove from inet csum the extraction header */
-       skb_postpull_rcsum(skb, start, OCELOT_LONG_PREFIX_LEN + OCELOT_TAG_LEN);
+       skb_postpull_rcsum(skb, start, OCELOT_TOTAL_TAG_LEN);
 
        packing(extraction, &src_port,  46, 43, OCELOT_TAG_LEN, UNPACK, 0);
        packing(extraction, &qos_class, 19, 17, OCELOT_TAG_LEN, UNPACK, 0);
@@ -231,7 +236,8 @@ static const struct dsa_device_ops ocelot_netdev_ops = {
        .proto                  = DSA_TAG_PROTO_OCELOT,
        .xmit                   = ocelot_xmit,
        .rcv                    = ocelot_rcv,
-       .overhead               = OCELOT_TAG_LEN + OCELOT_LONG_PREFIX_LEN,
+       .overhead               = OCELOT_TOTAL_TAG_LEN,
+       .promisc_on_master      = true,
 };
 
 MODULE_LICENSE("GPL v2");