[Arm-netbook] USB console idea

Bari Ari bari at onelabs.com
Tue Mar 6 13:05:31 GMT 2012

On 03/06/2012 06:20 AM, lkcl luke wrote:
> 2012/3/6 Henrik Nordström<henrik at henriknordstrom.net>:
>> Was thinking why not use the USB for console?
Do any of the ARM SOC USB ports support the EHCI Debug Port ?

In the x86 world a new USB debug class was started a few years ago since 
serial was depreciated and disappeared from most chipsets.

" The debug port provides a mode of operation that requires neither RAM 
nor a full USB stack. A handful of registers in the EHCI controller PCI 
configuration and BAR address space are used for all communication. All 
three transfer types are supported (OUT/SETUP/IN) but transfers can only 
be a maximum of 8 bytes and only one specific physical USB port can be 
used. A Debug Class compliant device is the only supported USB function 
that can be communicated with."


Has code examples for support and detection.


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