net: dsa: mv88e6xxx: Add RGMII delay to 88E6320

Currently, the .port_set_rgmii_delay hook is missing for the 88E6320
family, which causes failure to retrieve an IP address via DHCP.

Add mv88e6320_port_set_rgmii_delay() that allows applying the RGMII
delay for ports 2, 5, and 6, which are the only ports that can be used
in RGMII mode.

Tested on a custom i.MX8MN board connected to an 88E6320 switch.

This change also applies safely to the 88E6321 variant.

The only difference between 88E6320 versus 88E6321 is the temperature
grade and pinout.

They share exactly the same MDIO register map for ports 2, 5, and 6,
which are the only ports that can be used in RGMII mode.

Signed-off-by: Steffen Bätz <[e-mail]>
[fabio: Improved commit log and extended it to mv88e6321_ops]
Signed-off-by: Fabio Estevam <[e-mail]>
Reviewed-by: Andrew Lunn <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Jakub Kicinski <[e-mail]>

drivers/net/dsa/mv88e6xxx/chip.c

···
 	.phy_write = mv88e6xxx_g2_smi_phy_write,
 	.port_set_link = mv88e6xxx_port_set_link,
 	.port_sync_link = mv88e6xxx_port_sync_link,
+	.port_set_rgmii_delay = mv88e6320_port_set_rgmii_delay,
 	.port_set_speed_duplex = mv88e6185_port_set_speed_duplex,
 	.port_tag_remap = mv88e6095_port_tag_remap,
 	.port_set_frame_mode = mv88e6351_port_set_frame_mode,
···
 	.phy_write = mv88e6xxx_g2_smi_phy_write,
 	.port_set_link = mv88e6xxx_port_set_link,
 	.port_sync_link = mv88e6xxx_port_sync_link,
+	.port_set_rgmii_delay = mv88e6320_port_set_rgmii_delay,
 	.port_set_speed_duplex = mv88e6185_port_set_speed_duplex,
 	.port_tag_remap = mv88e6095_port_tag_remap,
 	.port_set_frame_mode = mv88e6351_port_set_frame_mode,

drivers/net/dsa/mv88e6xxx/port.c

···
 	return mv88e6xxx_port_set_rgmii_delay(chip, port, mode);
 }
 
+int mv88e6320_port_set_rgmii_delay(struct mv88e6xxx_chip *chip, int port,
+				   phy_interface_t mode)
+{
+	if (port != 2 && port != 5 && port != 6)
+		return -EOPNOTSUPP;
+
+	return mv88e6xxx_port_set_rgmii_delay(chip, port, mode);
+}
+
 int mv88e6xxx_port_set_link(struct mv88e6xxx_chip *chip, int port, int link)
 {
 	u16 reg;

drivers/net/dsa/mv88e6xxx/port.h

···
 
 int mv88e6185_port_set_pause(struct mv88e6xxx_chip *chip, int port,
 			     int pause);
+int mv88e6320_port_set_rgmii_delay(struct mv88e6xxx_chip *chip, int port,
+				   phy_interface_t mode);
 int mv88e6352_port_set_rgmii_delay(struct mv88e6xxx_chip *chip, int port,
 				   phy_interface_t mode);
 int mv88e6390_port_set_rgmii_delay(struct mv88e6xxx_chip *chip, int port,