Re: Enabling MUSB support

[Felipe Balbi <me@felipebalbi.com>]

On Fri, Aug 29, 2008 at 01:50:16PM -0700, David Brownell wrote:
> Right, that's why I thought I'd chase the easier host-side issue
> first.  Must have "apt-get install ..." working after all!!

hmm... sure.

> Were those self-powered devices, or bus-powered?  Descriptors
> are not entirely trustworthy about current usage.  Sometimes
> they represent worst-case; sometimes it's best-case.

bus-powered.

> > Do you have the BLACKLIST_HUB set? (just to be sure).
> 
> No, that's not set.

yet another new bug so, is it a full or high speed hub ?

> IMO it's the silicon that's buggy.  The specific window I kept seeing
> was between VBUS_ON and the 100msec later where it's expected to be
> stable.  During that window, VBUS is allowed to not be stable ... which
> is good, because that's when current spikes happen while charging the
> various capacitances involved.  (Cable, caps at either end, etc.)
> 
> I saw TUSB6010 reporting VBUS_ERR during that 100msec window ... and
> same thing with DaVinci.  Both needed retry logic to cope with the
> inappropriate VBUS fault reports.  The thing in common is the silicon
> IP, not the hardware.

Sure, musb is damn buggy and looks like it won't be fixed after all. At
least we're sure it's a silicon bug. I wonder if mentor has plans to fix
it ?!? A better dma engine would also be welcome, the whole "mode"
thingy is a mess.

btw, do you need me to help you debugging anything ? I can to the office
tomorrow and debug some stuff there if it's needed, otherwise I'll get
back to this only on monday.

-- 
balbi