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  • Author Author: colporteur
  • Date Created: Date Created
  • Views 5089 views
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  • Comments 13 comments
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Insight into lan78xx driver support for Pi

colporteur

Does anyone have any insight into lan78xx usb driver support for the Raspberry Pi?

 

I am attempting to use a Microchip PoE USB-C device to enabling networking to a Raspberry Pi4B. The work is part of a RoadTest for Microchip PoE to USB-CRegistered Power and Data Adapter .

 

A quick check with a command line lsmod shows no lan78xx driver. There is no /lib/modules/5.10.17-v7l+/kernel/net/usb to support the lan78xx as suggested in some posts I have found.

 

I did find this post https://wiki.seeedstudio.com/Dual-Gigabit-Ethernet-Carrier-Board-for-Raspberry-Pi-CM4/   and successfully completed the procedure for an Ethernet Port configuration.

image

 

A lan7800 module reference does appear for a command line lsmod after the install. The Microchip PoE USB-C lan7800 port is not detected when connected to the Pi. Still no reference to a lan78xx module appears in the directory structure.

 

The vendors site https://www.microchip.com/wwwproducts/en/LAN7800  indicates there has been support in the Linux kernel. My searches for Pi driver support has been limited. My understanding is lan78xx is a modules in the usb subdirectory when installed. I'm not seeing that for this kludge.

 

I'm thinking maybe I need a a dtsoverlay in the config.txt directory. Really not sure. I have gone as far as to load Ubuntu for the Pi to see if it is O/S related. That didn't prove fruitful.

 

I welcome any insight community members may have regarding network driver installs for the Pi. I will continue to hunt and peck to see if there is anything I have missed.

  • I have the unit working on my Raspberry Pi 4 (but needing a USB-C to A OTG adapter + USB-A to USB-C cable because mine is the version with the CC pin issue, so using the included captive USB-C to USB-C results in no LED/no power).

     

    In config.txt, I added otg_mode=1

    This is mandatory to enable the USB 2.0 OTG controller that services the USB-C port's data pins. If you don't add this line, you will only get power and no USB-Ethernet detection.

     

    On startup, it is automatically picked up on my installation of Raspberry Pi OS (Raspbian):

    [
0.000000] Linux version 5.10.17-v7l+ (dom@buildbot) (arm-linux-gnueabihf-gcc-8 (Ubuntu/Linaro 8.4.0-3ubuntu1) 8.4.0, GNU ld (GNU Binutils for Ubuntu) 2.34) #1414 SMP Fri Apr 30 13:20:47 BST 2021
[
1.394777] usbcore: registered new interface driver lan78xx
[
1.984215] usb 3-1: New USB device found, idVendor=0424, idProduct=7800, bcdDevice= 3.00
[
1.984263] usb 3-1: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[
1.984296] usb 3-1: Product: LAN7800
[
1.984324] usb 3-1: Manufacturer: Microchip
[
1.984353] usb 3-1: SerialNumber: 210460000404
[
2.271146] libphy: lan78xx-mdiobus: probed
[
2.271192] lan78xx 3-1:1.0 (unnamed net_device) (uninitialized): int urb period 64

     

    I did not need to install any drivers at all to get it working. I wasn't going to write about this until I delivered my RoadTest ... but seeing that you're rushing ahead into blogging, I thought I'd mention it.

     

    Why does your kernel command line have initcall_blacklist=lan78xx_driver_init? That's perhaps not a good thing ... could stop a driver from loading. Perhaps start from a fresh Raspberry Pi OS (Raspbian) and add otg_mode=1 and it should just work.

     

    - Gough

  • (On that page, under the Document tab, there is a driver section.

    If you click the one for the kernel version of your OS, you get a link to the driver tarball.)

     

    Edit: seems from your comments that you are on kernel 5.10. I didn't find a driver for it . But when I check linux git (and raspberry git), it seems to be part of the base code now. Odd.

  • Doesn't the PI 4 have a type c power connector?