[coreboot] EHCI Debug port support?

[Peter Stuge]

Hi,

TigerLiu at viatech.com.cn wrote:
> So how to use EHCI-debug-port device as the debug message output
> pipe?
> Could you  give a sample?

TigerLiu at viatech.com.cn wrote:
> Does coreboot support outputting debug message with a usb debug
> cable(NET20DC?) ?
> 
> Does anybody test it with coreboot?

coreboot does have support for using the NET20DC debug device as
console, but it is not very commonly used, so there may be issues.

I think the only person who used it recently is Stefan, on an Intel
chipset. When the support was added, several years ago, I believe it
was working also on an NVIDIA chipset.

Unfortunately I can not provide a simple example of how to use it,
because I haven't used it myself yet.

Currently there is no support for USB debug in the new Kconfig build
system, but the old style configuration and build system does support
it. Look for CONFIG_USBDEBUG_DIRECT=1 in Options.lb and/or Config.lb in
the src/mainboard directory for the board you are using, or add it if
it is not there. I'd like to add this to Kconfig also, especially if
it can be confirmed to work.

Note that the code relies on a data struct being untouched, it is
created just below CONFIG_LB_MEM_TOPK in RAM. (and also top of cache
while running with cache as RAM)


Good luck, and I welcome a progress report, if it works or not, if
you run into any trouble along the way. Thanks!


Kind regards,

//Peter