[PATCH] riscv: dts: sophgo: add cv1800b ethernet support overlay

Thu Oct 1 12:38:30 PDT 2026

The CV1800B SoC has a DWMAC controller connected to an internal 10/100
Ethernet PHY. Both the MAC (gmac0) and the MDIO multiplexer used to
reach the internal PHY are already described in cv180x.dtsi, but are
disabled by default.

Enable gmac0 and the MDIO multiplexer to make ethernet work.

Tested on a Milk-V Duo (CV1800B) with its IO base board. The link comes
up at 100Mbps/Full and the interface gets an address via DHCP.

This can not be enabled by default as others may want to use the same
pins as GPIO, that is the reason an overlay is being used.

Signed-off-by: Hiago De Franco <hfranco at baylibre.com>
---
Hi,

This is a continuation of patch [1]. The same patch was sent before [2],
and an overlay was suggested, altought it was not sent. Therefore I am
sending this overlay now.

U-Boot logs:

milkv_duo# setenv fdtoverlay_addr_r 0x82480000
milkv_duo# boot
** Booting bootflow 'mmc at 4310000.bootdev.part_1' with extlinux
1:	Poky (Yocto Project Reference Distro)
Retrieving file: /Image.gz
append: root=/dev/mmcblk0p2 ro rootwait console=ttyS0,115200 earlycon=sbi
Retrieving file: /cv1800b-milkv-duo.dtb
Retrieving file: /cv1800b-milkv-duo-eth.dtbo
   Uncompressing Kernel Image to 0
\## Flattened Device Tree blob at 82200000
   Booting using the fdt blob at 0x82200000
Working FDT set to 82200000
   Loading Device Tree to 0000000083560000, end 0000000083568fff ... OK
Working FDT set to 83560000

Kernel logs:

root at milkv-duo:~# ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq qlen 1000
    link/ether 22:9c:5e:8d:3b:0c brd ff:ff:ff:ff:ff:ff
    inet 192.168.0.124/24 brd 192.168.0.255 scope global eth0
       valid_lft forever preferred_lft forever
root at milkv-duo:~# dmesg | grep stmmaceth
[    0.580448] stmmaceth 4070000.ethernet: IRQ eth_wake_irq not found
[    0.587750] stmmaceth 4070000.ethernet: IRQ sfty not found
[    0.594165] stmmaceth 4070000.ethernet: Hash table entries set to unexpected value 0
[    0.604856] stmmaceth 4070000.ethernet: User ID: 0x10, Synopsys ID: 0x37
[    0.612359] stmmaceth 4070000.ethernet: 	DWMAC1000
[    0.617641] stmmaceth 4070000.ethernet: DMA HW capability register supported
[    0.625189] stmmaceth 4070000.ethernet: Active PHY interface: RMII (4)
[    0.632191] stmmaceth 4070000.ethernet: RX Checksum Offload Engine supported
[    0.639720] stmmaceth 4070000.ethernet: COE Type 2
[    0.644915] stmmaceth 4070000.ethernet: TX Checksum insertion supported
[    0.651995] stmmaceth 4070000.ethernet: Normal descriptors
[    0.657911] stmmaceth 4070000.ethernet: Ring mode enabled
[    0.663737] stmmaceth 4070000.ethernet: Enable RX Mitigation via HW Watchdog Timer
[    0.671939] stmmaceth 4070000.ethernet: device MAC address 22:9c:5e:8d:3b:0c
[   13.104870] stmmaceth 4070000.ethernet eth0: Register MEM_TYPE_PAGE_POOL RxQ-0
[   13.125037] stmmaceth 4070000.ethernet eth0: PHY [mdio_mux-0.0:01] driver [Generic PHY] (irq=POLL)
[   13.172421] stmmaceth 4070000.ethernet eth0: No Safety Features support found
[   13.203664] stmmaceth 4070000.ethernet eth0: IEEE 1588-2002 Timestamp supported
[   13.229963] stmmaceth 4070000.ethernet eth0: configuring for phy/internal link mode
[   15.278278] stmmaceth 4070000.ethernet eth0: Link is Up - 100Mbps/Full - flow control rx/tx

[1] https://lore.kernel.org/sophgo/20260930-milkv-duo-ethernet-v1-1-428ff137f5d3@baylibre.com/
[2] https://lore.kernel.org/sophgo/20260803163323.74414-1-chenyou910331@gmail.com/
---
 arch/riscv/boot/dts/sophgo/Makefile                   |  3 +++
 arch/riscv/boot/dts/sophgo/cv1800b-milkv-duo-eth.dtso | 17 +++++++++++++++++
 2 files changed, 20 insertions(+)

diff --git a/arch/riscv/boot/dts/sophgo/Makefile b/arch/riscv/boot/dts/sophgo/Makefile
index d5c80d4ff005..adea990ad912 100644
--- a/arch/riscv/boot/dts/sophgo/Makefile
+++ b/arch/riscv/boot/dts/sophgo/Makefile
@@ -1,5 +1,8 @@
 # SPDX-License-Identifier: GPL-2.0
 dtb-$(CONFIG_ARCH_SOPHGO) += cv1800b-milkv-duo.dtb
+cv1800b-milkv-duo-eth-dtbs := cv1800b-milkv-duo.dtb cv1800b-milkv-duo-eth.dtbo
+dtb-$(CONFIG_ARCH_SOPHGO) += cv1800b-milkv-duo-eth.dtb
+dtb-$(CONFIG_ARCH_SOPHGO) += cv1800b-milkv-duo-eth.dtbo
 dtb-$(CONFIG_ARCH_SOPHGO) += cv1812h-huashan-pi.dtb
 dtb-$(CONFIG_ARCH_SOPHGO) += sg2000-milkv-duo-s.dtb
 dtb-$(CONFIG_ARCH_SOPHGO) += sg2002-licheerv-nano-b.dtb
diff --git a/arch/riscv/boot/dts/sophgo/cv1800b-milkv-duo-eth.dtso b/arch/riscv/boot/dts/sophgo/cv1800b-milkv-duo-eth.dtso
new file mode 100644
index 000000000000..52c85b4e0155
--- /dev/null
+++ b/arch/riscv/boot/dts/sophgo/cv1800b-milkv-duo-eth.dtso
@@ -0,0 +1,17 @@
+// SPDX-License-Identifier: (GPL-2.0 OR MIT)
+/*
+ * Enable ethernet support on Milk-V Duo (CV1800B).
+ *
+ * Copyright (c) 2026, Hiago De Franco <hfranco at baylibre.com>
+ */
+
+/dts-v1/;
+/plugin/;
+
+&gmac0 {
+	status = "okay";
+};
+
+&mdio {
+	status = "okay";
+};

---
base-commit: d24e8ac715de2e16a53c144005b1863660a5fbea
change-id: 20261001-milkv-duo-eth-overlay-cf7738449a40

Best regards,
--  
Hiago


