[U-Boot] netconsole: USB Ethernet connection dropping with ping or tftpboot

["Jörg Krause" <jkrause@posteo.de>]

On Di, 2015-02-03 at 22:44 +0100, J?rg Krause wrote:
> I followed the instructions from Marek in 'M28 U-Boot Single-Wire Debug
> preview' to enable NetConsole:
> http://www.denx-cs.de/?q=blogm28singlewiredebug
> 
> I'm using mxsldr to flash the u-boot.sb image to RAM. This is the dmesg
> output from my host:
> 
>         [31048.492181] usb 3-13: new high-speed USB device number 24
>         using xhci_hcd
>         [31048.667617] cdc_ether 3-13:1.0 eth0: register 'cdc_ether' at
>         usb-0000:00:14.0-13, CDC Ethernet Device, 00:19:b8:00:00:01
>         [31048.669101] cdc_ether 3-13:1.0 enp0s20u13: renamed from eth0
>         [31048.696758] cdc_ether 3-13:1.0 enp0s20u13: kevent 12 may have
>         been dropped
> 
> I noticed the 'kevent 12 may have been dropped' message here.
> 
> Nevertheless, NetworkManager shows me a USB Ethernet connection and
> using './netconsole 10.0.0.2' I am able to communicate with the device,
> e.g. 'nand info' outputs correctly.
> 
> But if I use 'ping 10.0.0.1' or 'tftpboot u-boot.sb' the network
> connection drops. Both commands work fine if I switch back from
> netconsole to serial in-/output.
> 
> This is the output from dmesg:
>         [31620.215354] usb 3-13: USB disconnect, device number 24
>         [31620.215422] cdc_ether 3-13:1.0 enp0s20u13: unregister
>         'cdc_ether' usb-0000:00:14.0-13, CDC Ethernet Device
> 
> Do I missed something?

I managed to get serial console and netconsole muxing to work, so I can
see all the debug messages:

        Hit any key to stop autoboot:  5 using ci_udc, OUT ep- IN ep-
        STATUS ep-
        MAC 00:19:b8:00:00:02
        HOST MAC 00:19:b8:00:00:01
        high speed config #1: 2 mA, Ethernet Gadget, using CDC Ethernet
        USB network up!
         0 
        => tftp u-boot.sb
        using ci_udc, OUT ep- IN ep- STATUS ep-
        timeout sending packets to usb ethernet

This reminded me about an issue I had some months ago:
http://lists.denx.de/pipermail/u-boot/2014-July/182885.html

I enabled debug output in arch/arm/cpu/arm926ejs/cache.c and I get
error:
=> tftp u-boot.sb
using ci_udc, OUT ep- IN ep- STATUS ep-
CACHE: Misaligned operation at range [43f7b010, 43f7b070]

I removed the flush_cache() call in cmd_net.c:netboot_common() as
suggested by Marek in the thread. But the error message is still there.

Any idea?