netdev - Re: [PATCH net-next v14 3/4] net: dsa: yt921x: Add support for Motorcomm YT921x

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Message-ID: <60f98b3a-79de-494a-895f-4d1eb21a405a@gmail.com>
Date: Wed, 4 Feb 2026 14:12:46 +0700
From: michio da neko <michio.haiyaku@...il.com>
To: mmyangfl@...il.com
Cc: andrew@...n.ch, conor+dt@...nel.org, davem@...emloft.net,
 devicetree@...r.kernel.org, edumazet@...gle.com, horms@...nel.org,
 krzk+dt@...nel.org, kuba@...nel.org, linux-kernel@...r.kernel.org,
 linux@...linux.org.uk, netdev@...r.kernel.org, olteanv@...il.com,
 pabeni@...hat.com, robh@...nel.org
Subject: Re: [PATCH net-next v14 3/4] net: dsa: yt921x: Add support for
 Motorcomm YT921x

Hi David Yang,

I am testing your YT9215 driver on a CIG device (ODM for a carrier) 
which uses the Qualcomm IPQ5018 SoC paired with the Motorcomm YT9215S 
switch.

The switch itself is detected correctly via MDIO bitbang, but I am 
facing issues with the internal PHYs. They are detected with a specific 
ID |0x01e04281| which falls back to the "Generic PHY" driver, and the 
ports remain in |NO-CARRIER| state even when cables are plugged in. I 
tried the existing Motorcomm PHY driver but it does not seem to cover 
this specific ID.

Here is my setup details:

DTS Configuration: I am using phy-mode = "internal" for the ports. (Full 
DTS available here: 
https://github.com/michioxd/openwrt-wf810df/blob/1b37e3adee7ab6651430511af259687a5a57edc5/target/linux/qualcommax/files/arch/arm64/boot/dts/qcom/ipq5018-ax3000cv2.dts)

&mdio_bitbang {
     /* ... */
     yt9215: switch@1d {
         compatible = "motorcomm,yt9215";
         reg = <29>;
         /* ... */
         ethernet-ports {
             ethernet-port@0 {
                 reg = <0>;
                 phy-mode = "internal";
                 phy-handle = <&sw_phy0>;
             };
             /* ... */
         };
     };
};

dmesg Output: The chip ID is detected as 0x90020002, but PHYs are generic:

[   13.405614] yt921x gpio-1:1d: Motorcomm YT9215S ethernet switch, 
chipid: 0x90020002, chipmode: 0x2 0x0
[   14.004664] yt921x gpio-1:1d: configuring for fixed/2500base-x link mode
[   14.018058] yt921x gpio-1:1d: Link is Up - 2.5Gbps/Full - flow 
control off
[   14.097426] yt921x gpio-1:1d lan1 (uninitialized): PHY [gpio-1:1d:00] 
driver [Generic PHY] (irq=POLL)
[   14.160182] yt921x gpio-1:1d lan2 (uninitialized): PHY [gpio-1:1d:01] 
driver [Generic PHY] (irq=POLL)
[   14.226811] yt921x gpio-1:1d lan3 (uninitialized): PHY [gpio-1:1d:02] 
driver [Generic PHY] (irq=POLL)

ip link Output:

3: lan: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1508 qdisc fq_codel state 
UP qlen 1000
     link/ether ... brd ff:ff:ff:ff:ff:ff
4: lan1@lan: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc noqueue 
master br-lan state LOWERLAYERDOWN qlen 1000
     link/ether ... brd ff:ff:ff:ff:ff:ff
5: lan2@lan: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc noqueue 
master br-lan state LOWERLAYERDOWN qlen 1000
     link/ether ... brd ff:ff:ff:ff:ff:ff
6: lan3@lan: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc noqueue 
master br-lan state LOWERLAYERDOWN qlen 1000
     link/ether ... brd ff:ff:ff:ff:ff:ff

Have you encountered this PHY ID (0x01e04281) before? If this ID 
requires a driver patch, do you know if it shares the same register 
layout or behavior with any existing supported YT8xxx PHYs (like YT8511 
or YT8521)? Knowing its closest relative would help me attempt to add 
support for it in drivers/net/phy/motorcomm.c.

Any advice on how to bring up these ports would be appreciated.

Best regards, Michio

-- 
michio da neko
https://michioxd.ch

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