Merge branch 'dsa-tag-override'

Tobias Waldekranz says:

====================
net: dsa: Allow default tag protocol to be overridden from DT

This is a continuation of the work started in this patch:
https://lore.kernel.org/netdev/20210323102326.3677940-1-tobias@waldekranz.com/

In addition to the mv88e6xxx support to dynamically change the
protocol, it is now possible to override the protocol from the device
tree. This means that when a board vendor finds an incompatibility,
they can specify a working protocol in the DT, and users will not have
to worry about it.

Some background information:

In a system using an NXP T1023 SoC connected to a 6390X switch, we
noticed that TO_CPU frames where not reaching the CPU. This only
happened on hardware port 8. Looking at the DSA master interface
(dpaa-ethernet) we could see that an Rx error counter was bumped at
the same rate. The logs indicated a parser error.

It just so happens that a TO_CPU coming in on device 0, port 8, will
result in the first two bytes of the DSA tag being one of:

00 40
00 44
00 46

My guess was that since these values looked like 802.3 length fields,
the controller's parser would signal an error if the frame length did
not match what was in the header.

This was later confirmed using two different workarounds provided by
Vladimir. Unfortunately these either bypass or ignore the hardware
parser and thus robs working combinations of the ability to do RSS and
other nifty things. It was therefore decided to go with the option of
a DT override.

v1 -> v2:
  - Fail if the device does not support changing protocols instead of
    falling back to the default. (Andrew)
  - Only call change_tag_protocol on CPU ports. (Andrew/Vladimir)
  - Only allow changing the protocol on chips that have at least
    "undocumented" level of support for EDSA. (Andrew).
  - List the supported protocols in the binding documentation. I opted
    for only listing the protocols that I have tested. As more people
    test their drivers, they can add them. (Rob)

v2 -> v3:
  - Rename "dsa,tag-protocol" -> "dsa-tag-protocol". (Rob)
  - Some cleanups to 4/5. (Vladimir)
  - Add a comment detailing how tree/driver agreement on the tag
    protocol is enforced. (Vladimir).
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 85 insertions, 35 deletions

diff --git a/drivers/net/dsa/mv88e6xxx/chip.c b/drivers/net/dsa/mv88e6xxx/chip.c
index 9c4f8517c34b..9ff1a10993b1 100644
--- a/drivers/net/dsa/mv88e6xxx/chip.c
+++ b/drivers/net/dsa/mv88e6xxx/chip.c
@@ -2531,10 +2531,10 @@ static int mv88e6xxx_setup_port_mode(struct mv88e6xxx_chip *chip, int port)
 		return mv88e6xxx_set_port_mode_normal(chip, port);
 
 	/* Setup CPU port mode depending on its supported tag format */
-	if (chip->info->tag_protocol == DSA_TAG_PROTO_DSA)
+	if (chip->tag_protocol == DSA_TAG_PROTO_DSA)
 		return mv88e6xxx_set_port_mode_dsa(chip, port);
 
-	if (chip->info->tag_protocol == DSA_TAG_PROTO_EDSA)
+	if (chip->tag_protocol == DSA_TAG_PROTO_EDSA)
 		return mv88e6xxx_set_port_mode_edsa(chip, port);
 
 	return -EINVAL;
@@ -4786,7 +4786,6 @@ static const struct mv88e6xxx_info mv88e6xxx_table[] = {
 		.atu_move_port_mask = 0xf,
 		.pvt = true,
 		.multi_chip = true,
-		.tag_protocol = DSA_TAG_PROTO_DSA,
 		.ops = &mv88e6085_ops,
 	},
 
@@ -4807,7 +4806,6 @@ static const struct mv88e6xxx_info mv88e6xxx_table[] = {
 		.g1_irqs = 8,
 		.atu_move_port_mask = 0xf,
 		.multi_chip = true,
-		.tag_protocol = DSA_TAG_PROTO_DSA,
 		.ops = &mv88e6095_ops,
 	},
 
@@ -4830,7 +4828,7 @@ static const struct mv88e6xxx_info mv88e6xxx_table[] = {
 		.atu_move_port_mask = 0xf,
 		.pvt = true,
 		.multi_chip = true,
-		.tag_protocol = DSA_TAG_PROTO_EDSA,
+		.edsa_support = MV88E6XXX_EDSA_SUPPORTED,
 		.ops = &mv88e6097_ops,
 	},
 
@@ -4853,7 +4851,7 @@ static const struct mv88e6xxx_info mv88e6xxx_table[] = {
 		.atu_move_port_mask = 0xf,
 		.pvt = true,
 		.multi_chip = true,
-		.tag_protocol = DSA_TAG_PROTO_EDSA,
+		.edsa_support = MV88E6XXX_EDSA_SUPPORTED,
 		.ops = &mv88e6123_ops,
 	},
 
@@ -4874,7 +4872,6 @@ static const struct mv88e6xxx_info mv88e6xxx_table[] = {
 		.g1_irqs = 9,
 		.atu_move_port_mask = 0xf,
 		.multi_chip = true,
-		.tag_protocol = DSA_TAG_PROTO_DSA,
 		.ops = &mv88e6131_ops,
 	},
 
@@ -4898,7 +4895,7 @@ static const struct mv88e6xxx_info mv88e6xxx_table[] = {
 		.g2_irqs = 10,
 		.pvt = true,
 		.multi_chip = true,
-		.tag_protocol = DSA_TAG_PROTO_EDSA,
+		.edsa_support = MV88E6XXX_EDSA_SUPPORTED,
 		.ops = &mv88e6141_ops,
 	},
 
@@ -4921,7 +4918,7 @@ static const struct mv88e6xxx_info mv88e6xxx_table[] = {
 		.atu_move_port_mask = 0xf,
 		.pvt = true,
 		.multi_chip = true,
-		.tag_protocol = DSA_TAG_PROTO_EDSA,
+		.edsa_support = MV88E6XXX_EDSA_SUPPORTED,
 		.ptp_support = true,
 		.ops = &mv88e6161_ops,
 	},
@@ -4945,7 +4942,6 @@ static const struct mv88e6xxx_info mv88e6xxx_table[] = {
 		.atu_move_port_mask = 0xf,
 		.pvt = true,
 		.multi_chip = true,
-		.tag_protocol = DSA_TAG_PROTO_DSA,
 		.ptp_support = true,
 		.ops = &mv88e6165_ops,
 	},
@@ -4969,7 +4965,7 @@ static const struct mv88e6xxx_info mv88e6xxx_table[] = {
 		.atu_move_port_mask = 0xf,
 		.pvt = true,
 		.multi_chip = true,
-		.tag_protocol = DSA_TAG_PROTO_EDSA,
+		.edsa_support = MV88E6XXX_EDSA_SUPPORTED,
 		.ops = &mv88e6171_ops,
 	},
 
@@ -4993,7 +4989,7 @@ static const struct mv88e6xxx_info mv88e6xxx_table[] = {
 		.atu_move_port_mask = 0xf,
 		.pvt = true,
 		.multi_chip = true,
-		.tag_protocol = DSA_TAG_PROTO_EDSA,
+		.edsa_support = MV88E6XXX_EDSA_SUPPORTED,
 		.ops = &mv88e6172_ops,
 	},
 
@@ -5016,7 +5012,7 @@ static const struct mv88e6xxx_info mv88e6xxx_table[] = {
 		.atu_move_port_mask = 0xf,
 		.pvt = true,
 		.multi_chip = true,
-		.tag_protocol = DSA_TAG_PROTO_EDSA,
+		.edsa_support = MV88E6XXX_EDSA_SUPPORTED,
 		.ops = &mv88e6175_ops,
 	},
 
@@ -5040,7 +5036,7 @@ static const struct mv88e6xxx_info mv88e6xxx_table[] = {
 		.atu_move_port_mask = 0xf,
 		.pvt = true,
 		.multi_chip = true,
-		.tag_protocol = DSA_TAG_PROTO_EDSA,
+		.edsa_support = MV88E6XXX_EDSA_SUPPORTED,
 		.ops = &mv88e6176_ops,
 	},
 
@@ -5061,7 +5057,7 @@ static const struct mv88e6xxx_info mv88e6xxx_table[] = {
 		.g1_irqs = 8,
 		.atu_move_port_mask = 0xf,
 		.multi_chip = true,
-		.tag_protocol = DSA_TAG_PROTO_EDSA,
+		.edsa_support = MV88E6XXX_EDSA_SUPPORTED,
 		.ops = &mv88e6185_ops,
 	},
 
@@ -5079,7 +5075,6 @@ static const struct mv88e6xxx_info mv88e6xxx_table[] = {
 		.phy_base_addr = 0x0,
 		.global1_addr = 0x1b,
 		.global2_addr = 0x1c,
-		.tag_protocol = DSA_TAG_PROTO_DSA,
 		.age_time_coeff = 3750,
 		.g1_irqs = 9,
 		.g2_irqs = 14,
@@ -5109,7 +5104,6 @@ static const struct mv88e6xxx_info mv88e6xxx_table[] = {
 		.atu_move_port_mask = 0x1f,
 		.pvt = true,
 		.multi_chip = true,
-		.tag_protocol = DSA_TAG_PROTO_DSA,
 		.ops = &mv88e6190x_ops,
 	},
 
@@ -5132,7 +5126,6 @@ static const struct mv88e6xxx_info mv88e6xxx_table[] = {
 		.atu_move_port_mask = 0x1f,
 		.pvt = true,
 		.multi_chip = true,
-		.tag_protocol = DSA_TAG_PROTO_DSA,
 		.ptp_support = true,
 		.ops = &mv88e6191_ops,
 	},
@@ -5155,7 +5148,6 @@ static const struct mv88e6xxx_info mv88e6xxx_table[] = {
 		.atu_move_port_mask = 0x1f,
 		.pvt = true,
 		.multi_chip = true,
-		.tag_protocol = DSA_TAG_PROTO_DSA,
 		.ptp_support = true,
 		.ops = &mv88e6393x_ops,
 	},
@@ -5178,7 +5170,6 @@ static const struct mv88e6xxx_info mv88e6xxx_table[] = {
 		.atu_move_port_mask = 0x1f,
 		.pvt = true,
 		.multi_chip = true,
-		.tag_protocol = DSA_TAG_PROTO_DSA,
 		.ptp_support = true,
 		.ops = &mv88e6393x_ops,
 	},
@@ -5205,7 +5196,6 @@ static const struct mv88e6xxx_info mv88e6xxx_table[] = {
 		.g2_irqs = 10,
 		.atu_move_port_mask = 0xf,
 		.dual_chip = true,
-		.tag_protocol = DSA_TAG_PROTO_DSA,
 		.ptp_support = true,
 		.ops = &mv88e6250_ops,
 	},
@@ -5230,7 +5220,7 @@ static const struct mv88e6xxx_info mv88e6xxx_table[] = {
 		.atu_move_port_mask = 0xf,
 		.pvt = true,
 		.multi_chip = true,
-		.tag_protocol = DSA_TAG_PROTO_EDSA,
+		.edsa_support = MV88E6XXX_EDSA_SUPPORTED,
 		.ptp_support = true,
 		.ops = &mv88e6240_ops,
 	},
@@ -5252,7 +5242,6 @@ static const struct mv88e6xxx_info mv88e6xxx_table[] = {
 		.g2_irqs = 10,
 		.atu_move_port_mask = 0xf,
 		.dual_chip = true,
-		.tag_protocol = DSA_TAG_PROTO_DSA,
 		.ptp_support = true,
 		.ops = &mv88e6250_ops,
 	},
@@ -5276,7 +5265,6 @@ static const struct mv88e6xxx_info mv88e6xxx_table[] = {
 		.atu_move_port_mask = 0x1f,
 		.pvt = true,
 		.multi_chip = true,
-		.tag_protocol = DSA_TAG_PROTO_DSA,
 		.ptp_support = true,
 		.ops = &mv88e6290_ops,
 	},
@@ -5301,7 +5289,7 @@ static const struct mv88e6xxx_info mv88e6xxx_table[] = {
 		.atu_move_port_mask = 0xf,
 		.pvt = true,
 		.multi_chip = true,
-		.tag_protocol = DSA_TAG_PROTO_EDSA,
+		.edsa_support = MV88E6XXX_EDSA_SUPPORTED,
 		.ptp_support = true,
 		.ops = &mv88e6320_ops,
 	},
@@ -5325,7 +5313,7 @@ static const struct mv88e6xxx_info mv88e6xxx_table[] = {
 		.g2_irqs = 10,
 		.atu_move_port_mask = 0xf,
 		.multi_chip = true,
-		.tag_protocol = DSA_TAG_PROTO_EDSA,
+		.edsa_support = MV88E6XXX_EDSA_SUPPORTED,
 		.ptp_support = true,
 		.ops = &mv88e6321_ops,
 	},
@@ -5350,7 +5338,7 @@ static const struct mv88e6xxx_info mv88e6xxx_table[] = {
 		.g2_irqs = 10,
 		.pvt = true,
 		.multi_chip = true,
-		.tag_protocol = DSA_TAG_PROTO_EDSA,
+		.edsa_support = MV88E6XXX_EDSA_SUPPORTED,
 		.ptp_support = true,
 		.ops = &mv88e6341_ops,
 	},
@@ -5374,7 +5362,7 @@ static const struct mv88e6xxx_info mv88e6xxx_table[] = {
 		.atu_move_port_mask = 0xf,
 		.pvt = true,
 		.multi_chip = true,
-		.tag_protocol = DSA_TAG_PROTO_EDSA,
+		.edsa_support = MV88E6XXX_EDSA_SUPPORTED,
 		.ops = &mv88e6350_ops,
 	},
 
@@ -5397,7 +5385,7 @@ static const struct mv88e6xxx_info mv88e6xxx_table[] = {
 		.atu_move_port_mask = 0xf,
 		.pvt = true,
 		.multi_chip = true,
-		.tag_protocol = DSA_TAG_PROTO_EDSA,
+		.edsa_support = MV88E6XXX_EDSA_SUPPORTED,
 		.ops = &mv88e6351_ops,
 	},
 
@@ -5421,7 +5409,7 @@ static const struct mv88e6xxx_info mv88e6xxx_table[] = {
 		.atu_move_port_mask = 0xf,
 		.pvt = true,
 		.multi_chip = true,
-		.tag_protocol = DSA_TAG_PROTO_EDSA,
+		.edsa_support = MV88E6XXX_EDSA_SUPPORTED,
 		.ptp_support = true,
 		.ops = &mv88e6352_ops,
 	},
@@ -5445,7 +5433,7 @@ static const struct mv88e6xxx_info mv88e6xxx_table[] = {
 		.atu_move_port_mask = 0x1f,
 		.pvt = true,
 		.multi_chip = true,
-		.tag_protocol = DSA_TAG_PROTO_DSA,
+		.edsa_support = MV88E6XXX_EDSA_UNDOCUMENTED,
 		.ptp_support = true,
 		.ops = &mv88e6390_ops,
 	},
@@ -5469,7 +5457,7 @@ static const struct mv88e6xxx_info mv88e6xxx_table[] = {
 		.atu_move_port_mask = 0x1f,
 		.pvt = true,
 		.multi_chip = true,
-		.tag_protocol = DSA_TAG_PROTO_DSA,
+		.edsa_support = MV88E6XXX_EDSA_UNDOCUMENTED,
 		.ptp_support = true,
 		.ops = &mv88e6390x_ops,
 	},
@@ -5492,7 +5480,6 @@ static const struct mv88e6xxx_info mv88e6xxx_table[] = {
 		.atu_move_port_mask = 0x1f,
 		.pvt = true,
 		.multi_chip = true,
-		.tag_protocol = DSA_TAG_PROTO_DSA,
 		.ptp_support = true,
 		.ops = &mv88e6393x_ops,
 	},
@@ -5561,7 +5548,45 @@ static enum dsa_tag_protocol mv88e6xxx_get_tag_protocol(struct dsa_switch *ds,
 {
 	struct mv88e6xxx_chip *chip = ds->priv;
 
-	return chip->info->tag_protocol;
+	return chip->tag_protocol;
+}
+
+static int mv88e6xxx_change_tag_protocol(struct dsa_switch *ds, int port,
+					 enum dsa_tag_protocol proto)
+{
+	struct mv88e6xxx_chip *chip = ds->priv;
+	enum dsa_tag_protocol old_protocol;
+	int err;
+
+	switch (proto) {
+	case DSA_TAG_PROTO_EDSA:
+		switch (chip->info->edsa_support) {
+		case MV88E6XXX_EDSA_UNSUPPORTED:
+			return -EPROTONOSUPPORT;
+		case MV88E6XXX_EDSA_UNDOCUMENTED:
+			dev_warn(chip->dev, "Relying on undocumented EDSA tagging behavior\n");
+			fallthrough;
+		case MV88E6XXX_EDSA_SUPPORTED:
+			break;
+		}
+		break;
+	case DSA_TAG_PROTO_DSA:
+		break;
+	default:
+		return -EPROTONOSUPPORT;
+	}
+
+	old_protocol = chip->tag_protocol;
+	chip->tag_protocol = proto;
+
+	mv88e6xxx_reg_lock(chip);
+	err = mv88e6xxx_setup_port_mode(chip, port);
+	mv88e6xxx_reg_unlock(chip);
+
+	if (err)
+		chip->tag_protocol = old_protocol;
+
+	return err;
 }
 
 static int mv88e6xxx_port_mdb_add(struct dsa_switch *ds, int port,
@@ -6026,6 +6051,7 @@ static int mv88e6xxx_crosschip_lag_leave(struct dsa_switch *ds, int sw_index,
 
 static const struct dsa_switch_ops mv88e6xxx_switch_ops = {
 	.get_tag_protocol	= mv88e6xxx_get_tag_protocol,
+	.change_tag_protocol	= mv88e6xxx_change_tag_protocol,
 	.setup			= mv88e6xxx_setup,
 	.teardown		= mv88e6xxx_teardown,
 	.phylink_validate	= mv88e6xxx_validate,
@@ -6206,6 +6232,11 @@ static int mv88e6xxx_probe(struct mdio_device *mdiodev)
 	if (err)
 		goto out;
 
+	if (chip->info->edsa_support == MV88E6XXX_EDSA_SUPPORTED)
+		chip->tag_protocol = DSA_TAG_PROTO_EDSA;
+	else
+		chip->tag_protocol = DSA_TAG_PROTO_DSA;
+
 	mv88e6xxx_phy_init(chip);
 
 	if (chip->info->ops->get_eeprom) {
diff --git a/drivers/net/dsa/mv88e6xxx/chip.h b/drivers/net/dsa/mv88e6xxx/chip.h
index bce6e0dc8535..4f116f73a74b 100644
--- a/drivers/net/dsa/mv88e6xxx/chip.h
+++ b/drivers/net/dsa/mv88e6xxx/chip.h
@@ -96,6 +96,22 @@ enum mv88e6xxx_family {
 	MV88E6XXX_FAMILY_6393,	/* 6191X 6193X 6393X */
 };
 
+/**
+ * enum mv88e6xxx_edsa_support - Ethertype DSA tag support level
+ * @MV88E6XXX_EDSA_UNSUPPORTED:  Device has no support for EDSA tags
+ * @MV88E6XXX_EDSA_UNDOCUMENTED: Documentation indicates that
+ *                               egressing FORWARD frames with an EDSA
+ *                               tag is reserved for future use, but
+ *                               empirical data shows that this mode
+ *                               is supported.
+ * @MV88E6XXX_EDSA_SUPPORTED:    EDSA tags are fully supported.
+ */
+enum mv88e6xxx_edsa_support {
+	MV88E6XXX_EDSA_UNSUPPORTED = 0,
+	MV88E6XXX_EDSA_UNDOCUMENTED,
+	MV88E6XXX_EDSA_SUPPORTED,
+};
+
 struct mv88e6xxx_ops;
 
 struct mv88e6xxx_info {
@@ -133,7 +149,7 @@ struct mv88e6xxx_info {
 	 */
 	bool dual_chip;
 
-	enum dsa_tag_protocol tag_protocol;
+	enum mv88e6xxx_edsa_support edsa_support;
 
 	/* Mask for FromPort and ToPort value of PortVec used in ATU Move
 	 * operation. 0 means that the ATU Move operation is not supported.
@@ -261,6 +277,9 @@ struct mv88e6xxx_region_priv {
 struct mv88e6xxx_chip {
 	const struct mv88e6xxx_info *info;
 
+	/* Currently configured tagging protocol */
+	enum dsa_tag_protocol tag_protocol;
+
 	/* The dsa_switch this private structure is related to */
 	struct dsa_switch *ds;