net: dsa: realtek-smi: add rtl8365mb subdriver for RTL8365MB-VC

This patch adds a realtek-smi subdriver for the RTL8365MB-VC 4+1 port
10/100/1000M Ethernet switch controller. The driver has been developed
based on a GPL-licensed OS-agnostic Realtek vendor driver known as
rtl8367c found in the OpenWrt source tree.

Despite the name, the RTL8365MB-VC has an entirely different register
layout to the already-supported RTL8366RB ASIC. Notwithstanding this,
the structure of the rtl8365mb subdriver is based on the rtl8366rb
subdriver and makes use of the rtl8366 helper library for VLAN
configuration. Like the 'rb, it establishes its own irqchip to handle
cascaded PHY link status interrupts.

The RTL8365MB-VC is a capable switch and provides a number of offload
features that are not yet supported by this subdriver. However, the
basic functionality should be the same as that the rtl8366rb, modulo LED
support, Energy-Efficient Ethernet (EEE), and MTU configuration. Support
for these features - and more - may follow.

One more thing. Realtek's nomenclature for switches makes it hard to
know exactly what other ASICs might be supported by this driver. The
vendor driver goes by the name rtl8367c, but as far as I can tell, no
chip actually exists under this name. As such, the subdriver is named
rtl8365mb to emphasize the potentially limited support. But it is clear
from the vendor sources that a number of other more advanced switches
share a similar register layout, and further support should not be too
hard to add given access to the relevant hardware. With this in mind,
the subdriver has been written with as few assumptions about the
particular chip as is reasonable. But the RTL8365MB-VC is the only
hardware I have available, so some further work is surely needed.

Signed-off-by: Alvin Šipraga <alsi@bang-olufsen.dk>
Co-developed-by: Michael Rasmussen <mir@bang-olufsen.dk>
Signed-off-by: Michael Rasmussen <mir@bang-olufsen.dk>

drivers/net/dsa/Kconfig

@@ -70,6 +70,7 @@ config NET_DSA_QCA8K
 config NET_DSA_REALTEK_SMI
 	tristate "Realtek SMI Ethernet switch family support"
 	select NET_DSA_TAG_RTL4_A
+	select NET_DSA_TAG_RTL8_4
 	select FIXED_PHY
 	select IRQ_DOMAIN
 	select REALTEK_PHY

drivers/net/dsa/Makefile

@@ -10,7 +10,7 @@ obj-$(CONFIG_NET_DSA_MT7530)	+= mt7530.o
 obj-$(CONFIG_NET_DSA_MV88E6060) += mv88e6060.o
 obj-$(CONFIG_NET_DSA_QCA8K)	+= qca8k.o
 obj-$(CONFIG_NET_DSA_REALTEK_SMI) += realtek-smi.o
-realtek-smi-objs		:= realtek-smi-core.o rtl8366.o rtl8366rb.o
+realtek-smi-objs		:= realtek-smi-core.o rtl8366.o rtl8366rb.o rtl8365mb.o
 obj-$(CONFIG_NET_DSA_SMSC_LAN9303) += lan9303-core.o
 obj-$(CONFIG_NET_DSA_SMSC_LAN9303_I2C) += lan9303_i2c.o
 obj-$(CONFIG_NET_DSA_SMSC_LAN9303_MDIO) += lan9303_mdio.o

drivers/net/dsa/realtek-smi-core.c

@@ -490,6 +490,10 @@ static const struct of_device_id realtek_smi_of_match[] = {
 		.compatible = "realtek,rtl8366s",
 		.data = NULL,
 	},
+	{
+		.compatible = "realtek,rtl8365mb",
+		.data = &rtl8365mb_variant,
+	},
 	{ /* sentinel */ },
 };
 MODULE_DEVICE_TABLE(of, realtek_smi_of_match);

drivers/net/dsa/realtek-smi-core.h

@@ -144,5 +144,6 @@ int rtl8366_get_sset_count(struct dsa_switch *ds, int port, int sset);
 void rtl8366_get_ethtool_stats(struct dsa_switch *ds, int port, uint64_t *data);
 
 extern const struct realtek_smi_variant rtl8366rb_variant;
+extern const struct realtek_smi_variant rtl8365mb_variant;
 
 #endif /*  _REALTEK_SMI_H */