net: dsa: mv88e6xxx: Use chip-wide max frame size for MTU

Some of the chips in the mv88e6xxx family don't support jumbo
configuration per port. But they do have a chip-wide max frame size that
can be used. Use this to approximate the behaviour of configuring a port
based MTU.
Signed-off-by: Chris Packham <chris.packham@alliedtelesis.co.nz>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/dsa/mv88e6xxx/chip.c

@@ -2699,6 +2699,8 @@ static int mv88e6xxx_get_max_mtu(struct dsa_switch *ds, int port)
 
 	if (chip->info->ops->port_set_jumbo_size)
 		return 10240;
+	else if (chip->info->ops->set_max_frame_size)
+		return 1632;
 	return 1522;
 }
 
@@ -2710,6 +2712,8 @@ static int mv88e6xxx_change_mtu(struct dsa_switch *ds, int port, int new_mtu)
 	mv88e6xxx_reg_lock(chip);
 	if (chip->info->ops->port_set_jumbo_size)
 		ret = chip->info->ops->port_set_jumbo_size(chip, port, new_mtu);
+	else if (chip->info->ops->set_max_frame_size)
+		ret = chip->info->ops->set_max_frame_size(chip, new_mtu);
 	else
 		if (new_mtu > 1522)
 			ret = -EINVAL;
@@ -3450,6 +3454,7 @@ static const struct mv88e6xxx_ops mv88e6085_ops = {
 	.vtu_getnext = mv88e6352_g1_vtu_getnext,
 	.vtu_loadpurge = mv88e6352_g1_vtu_loadpurge,
 	.phylink_validate = mv88e6185_phylink_validate,
+	.set_max_frame_size = mv88e6185_g1_set_max_frame_size,
 };
 
 static const struct mv88e6xxx_ops mv88e6095_ops = {
@@ -3478,6 +3483,7 @@ static const struct mv88e6xxx_ops mv88e6095_ops = {
 	.vtu_getnext = mv88e6185_g1_vtu_getnext,
 	.vtu_loadpurge = mv88e6185_g1_vtu_loadpurge,
 	.phylink_validate = mv88e6185_phylink_validate,
+	.set_max_frame_size = mv88e6185_g1_set_max_frame_size,
 };
 
 static const struct mv88e6xxx_ops mv88e6097_ops = {
@@ -3515,6 +3521,7 @@ static const struct mv88e6xxx_ops mv88e6097_ops = {
 	.vtu_getnext = mv88e6352_g1_vtu_getnext,
 	.vtu_loadpurge = mv88e6352_g1_vtu_loadpurge,
 	.phylink_validate = mv88e6185_phylink_validate,
+	.set_max_frame_size = mv88e6185_g1_set_max_frame_size,
 };
 
 static const struct mv88e6xxx_ops mv88e6123_ops = {
@@ -3549,6 +3556,7 @@ static const struct mv88e6xxx_ops mv88e6123_ops = {
 	.vtu_getnext = mv88e6352_g1_vtu_getnext,
 	.vtu_loadpurge = mv88e6352_g1_vtu_loadpurge,
 	.phylink_validate = mv88e6185_phylink_validate,
+	.set_max_frame_size = mv88e6185_g1_set_max_frame_size,
 };
 
 static const struct mv88e6xxx_ops mv88e6131_ops = {
@@ -3938,6 +3946,7 @@ static const struct mv88e6xxx_ops mv88e6185_ops = {
 	.vtu_getnext = mv88e6185_g1_vtu_getnext,
 	.vtu_loadpurge = mv88e6185_g1_vtu_loadpurge,
 	.phylink_validate = mv88e6185_phylink_validate,
+	.set_max_frame_size = mv88e6185_g1_set_max_frame_size,
 };
 
 static const struct mv88e6xxx_ops mv88e6190_ops = {

drivers/net/dsa/mv88e6xxx/chip.h

@@ -552,6 +552,9 @@ struct mv88e6xxx_ops {
 	void (*phylink_validate)(struct mv88e6xxx_chip *chip, int port,
 				 unsigned long *mask,
 				 struct phylink_link_state *state);
+
+	/* Max Frame Size */
+	int (*set_max_frame_size)(struct mv88e6xxx_chip *chip, int mtu);
 };
 
 struct mv88e6xxx_irq_ops {

drivers/net/dsa/mv88e6xxx/global1.c

@@ -196,6 +196,23 @@ int mv88e6185_g1_ppu_disable(struct mv88e6xxx_chip *chip)
 	return mv88e6185_g1_wait_ppu_disabled(chip);
 }
 
+int mv88e6185_g1_set_max_frame_size(struct mv88e6xxx_chip *chip, int mtu)
+{
+	u16 val;
+	int err;
+
+	err = mv88e6xxx_g1_read(chip, MV88E6XXX_G1_CTL1, &val);
+	if (err)
+		return err;
+
+	val &= ~MV88E6185_G1_CTL1_MAX_FRAME_1632;
+
+	if (mtu > 1518)
+		val |= MV88E6185_G1_CTL1_MAX_FRAME_1632;
+
+	return mv88e6xxx_g1_write(chip, MV88E6XXX_G1_CTL1, val);
+}
+
 /* Offset 0x10: IP-PRI Mapping Register 0
  * Offset 0x11: IP-PRI Mapping Register 1
  * Offset 0x12: IP-PRI Mapping Register 2

drivers/net/dsa/mv88e6xxx/global1.h

@@ -282,6 +282,8 @@ int mv88e6250_g1_reset(struct mv88e6xxx_chip *chip);
 int mv88e6185_g1_ppu_enable(struct mv88e6xxx_chip *chip);
 int mv88e6185_g1_ppu_disable(struct mv88e6xxx_chip *chip);
 
+int mv88e6185_g1_set_max_frame_size(struct mv88e6xxx_chip *chip, int mtu);
+
 int mv88e6xxx_g1_stats_snapshot(struct mv88e6xxx_chip *chip, int port);
 int mv88e6320_g1_stats_snapshot(struct mv88e6xxx_chip *chip, int port);
 int mv88e6390_g1_stats_snapshot(struct mv88e6xxx_chip *chip, int port);