From: David Brownell <david-b@pacbell.net>
To: Felipe Balbi <me@felipebalbi.com>, Bryan Wu <cooloney@kernel.org>
Cc: tony@atomide.com, linux-omap@vger.kernel.org
Subject: Re: [Help 1/2] MUSB: ZiO! CF card reader will trigger a change from MUSB host mode to MUSB peripheral mode
Date: Mon, 7 Apr 2008 09:05:09 -0700 [thread overview]
Message-ID: <200804070905.10048.david-b@pacbell.net> (raw)
In-Reply-To: <af73f7a75d15439b4761e7b0baa612cf@felipebalbi.com>
On Monday 07 April 2008, Felipe Balbi wrote:
> I recall having some issues on 100mA devices. During enumeration some
> current spikes a few mAs above 100mA were occuring and we couldn't
> enumerate the device due to vbus_err interrupt.
Yeah, I think the Mentor core is unduly sensitive to voltage
fluctuation during enumeration. There's supposed to be about
100 msec before VBUS must stabilize ... but the silicon doesn't
seem to accept routine instabilities in that period, and then
reports inappropriate VBUS errors.
> If you check drivers/usb/musb/tusb6010.c you'll see that we've
> implemented a retry condition for those cases. The same retry can
> be found in musb_core.c
The DaVinci support needed the same kind of logic. All in
all this is painful stuff to sort out, and it seems that
each platform rediscovers it. It would be better if the
silicon itself weren't fighting back so hard...
- Dave
next prev parent reply other threads:[~2008-04-07 16:05 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-04-07 10:15 [Help 1/2] MUSB: ZiO! CF card reader will trigger a change from MUSB host mode to MUSB peripheral mode Bryan Wu
2008-04-07 10:19 ` Felipe Balbi
2008-04-07 10:35 ` Bryan Wu
2008-04-07 10:46 ` Felipe Balbi
2008-04-07 11:08 ` Bryan Wu
2008-04-07 12:38 ` Felipe Balbi
2008-04-07 16:05 ` David Brownell [this message]
2008-04-07 17:48 ` Felipe Balbi
2008-04-08 7:06 ` Bryan Wu
2008-04-10 11:24 ` Bryan Wu
2008-04-11 14:59 ` Felipe Balbi
2008-04-11 16:13 ` David Brownell
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