[PATCH 3/3] fix-stop-sitting-printing-in-time-critical-context.patch

Harald Welte laforge at openmoko.org
Tue Aug 26 20:00:19 CEST 2008

On Fri, Aug 01, 2008 at 07:54:23AM +0100, Andy Green wrote:
> Someone left us a big fat warning in USB device code
> 	/* Don't ever put [serial] debugging in non-error codepaths here, it
> 	 * will violate the tight timing constraints of this USB Device
> 	 * controller (and lead to bus enumeration failures) */

just a minor sidenote: It was me who wrote that warning. I must have literally
lost a week in finding this out.  In the end I even found out that if the CPU
core clock is not running fast enough, the timing constraints are violated and
the enumeration fails.  

It's a problem that you usually just don't think would happen on a
several-hundred-MHz core with something als comparatively slow as 11MHz USB
behind a device controller that's supposed to handle the most critical stuff
and offer a FIFO-based interface.

- Harald Welte <laforge at openmoko.org>          	        http://openmoko.org/
Software for the world's first truly open Free Software mobile phone

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