Secret diaries of a suspend/resume debugger

[Daniel J Blueman]

On Tue, Jun 22, 2010 at 11:02 AM, Lee Jones <lee.jones at canonical.com> wrote:
>> Good story and a superb writeup.
>>
>> I've been using a USB debug device for console access via the EHCI
>> debug port on legacy-free systems, and I wonder if it would prove more
>> useful than the USB-serial mechanism in this case...
>>
>> It's quite handy now that support is enabled in the Maverick kernel
>> (or should be by now), but it's a shame in that USB debug devices seem
>> hard to find, particularly outside the US.
>
> Thank you Dan, that means a lot.
>
> Which device are you using? Do you have a web link?

This is what I have:
http://www.semiconductorstore.com/cart/pc/viewPrd.asp?idproduct=12083

it has two NET2270 USB controllers:
http://www.physics.utoronto.ca/~astummer/pub/mirror/Docs/Engineering/NET2270%20PlxTech,%20USB2.0%20device.pdf

and a Parallax SX28AC/SS-G microcontroller:
http://www.parallax.com/dl/docs/prod/datast/SX20AC-SX28AC-Data-v1.6.pdf

Perhaps they are rarer due to the complexity and reliance on (now
deprecated) parts...

> To be honest, I think it would suffer in the same way as my USB->Serial device.
>
> Once USB is put to sleep, all bets are off.

Since this is used for early printk, it is simple and thus robust (by
virtue of needing only the console lock IIRC). Preventing USB PHY
power-down may by sufficient to catch all the console output across
pre and post-suspend.

Dan
-- 
Daniel J Blueman