From mboxrd@z Thu Jan 1 00:00:00 1970 From: marex@denx.de (Marek Vasut) Date: Mon, 8 Jul 2013 22:56:38 +0200 Subject: Chipidea usb otg support for IMX/MXS (device functionality) In-Reply-To: References: <51A5A808.2070803@digi.com> <201307070310.00973.marex@denx.de> Message-ID: <201307082256.38642.marex@denx.de> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org Hi Peter, > > -----Original Message----- > > From: Marek Vasut [mailto:marex at denx.de] > > Sent: Sunday, July 07, 2013 9:10 AM > > To: Chen Peter-B29397 > > Cc: shawn.guo at linaro.org; Michael Grzeschik; maxime.ripard at free- > > electrons.com; Hector Palacios; linux-usb at vger.kernel.org; > > s.hauer at pengutronix.de; alexander.shishkin at linux.intel.com; Estevam > > Fabio-R49496; Marc Kleine-Budde; m.grzeschik at pengutronix.de; linux-arm- > > kernel at lists.infradead.org > > Subject: Re: Chipidea usb otg support for IMX/MXS (device functionality) > > > > Hi Peter, > > > > > > Where can I measure this? > > > > > > > > > Two possible reasons: > > > > > > > > > > 1. You have not gpio control for vbus toggle when role switches. > > > > > > > > This works well. > > > > > > > > > 2. Your hardware has some problems that the vbus can't lower than > > > > 0.8v. > > > > > > How can I check that? > > > > > > Just measure the voltage of your otg vbus pin. > > > > It's 2.5 volt for me. What am I supposed to observe happening there? > > http://marc.info/?l=linux-usb&m=137242465920952&w=2 Dang, must have missed that one, sorry. The VBUS is slowly discharging from around 5V to 2.5V , what does that tell me? Best regards, Marek Vasut