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

[Stephen Warren]

On 02/05/2015 04:21 AM, Jörg Krause wrote:
> On Di, 2015-02-03 at 22:44 +0100, Jörg 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.

Perhaps make flush_cache() a macro that also passes in the file/line 
number where it's called from, and print those out along with he 
"misaligned operation" error message?

(or find some other way to perform a stack dump from within that function).