From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Brownell 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 Message-ID: <200804070905.10048.david-b@pacbell.net> References: <386072610804070408q16c5ffa1u6a0c2e35295aa327@mail.gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from smtp111.sbc.mail.mud.yahoo.com ([68.142.198.210]:35250 "HELO smtp111.sbc.mail.mud.yahoo.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1754086AbYDGQFv (ORCPT ); Mon, 7 Apr 2008 12:05:51 -0400 In-Reply-To: Content-Disposition: inline Sender: linux-omap-owner@vger.kernel.org List-Id: linux-omap@vger.kernel.org To: Felipe Balbi , Bryan Wu Cc: tony@atomide.com, linux-omap@vger.kernel.org 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