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From: Tony Lindgren <tony@atomide.com>
To: Markus Pargmann <mpa@pengutronix.de>
Cc: "Benoît Cousson" <bcousson@baylibre.com>,
	linux-omap@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
	kernel@pengutronix.de
Subject: Re: [PATCH] arm: dtsi: am335x-bone-common, usb0 is peripheral only
Date: Thu, 13 Feb 2014 15:25:52 -0800	[thread overview]
Message-ID: <20140213232552.GR28216@atomide.com> (raw)
In-Reply-To: <20140213231333.GK31787@pengutronix.de>

* Markus Pargmann <mpa@pengutronix.de> [140213 15:16]:
> Hi,
> 
> On Thu, Feb 13, 2014 at 02:54:38PM -0800, Tony Lindgren wrote:
> > * Markus Pargmann <mpa@pengutronix.de> [140111 06:03]:
> > > The PMIC is using usb0 vbus line as power source. It is also connected
> > > to the am335x processor as vbus sense. But there is no possibility to
> > > pullup usb0 vbus to operate as host. This patch fixes the dr_mode of usb0.
> > 
> > That's the MUSB? AFAIK it's not possible to operate MUSB in peripheral
> > only mode because the hardware does what it wants based on the ID
> > pin state.
> 
> Yes that's MUSB. The am335x reference manual describes that it is
> possible to force peripheral/host mode by setting bit 7 (IDDIG_MUX) in
> register USBnMODE to 1. Then it uses the bit written in bit 8 (IDDIG) of
> register USBnMODE to set host/peripheral mode.

OK
 
> I am not sure if the driver supports it yet but I think the DTS should
> contain the correct mode nevertheless, especially to avoid starting the
> otg loops in the musb driver.

Well there's one more thing to consider.. I think in the OTG role change
case the VBUS is still driven externally from the original host, so the
lack of VBUS does not always mean that host mode should be disabled.

Regards,

Tony

WARNING: multiple messages have this Message-ID (diff)
From: tony@atomide.com (Tony Lindgren)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH] arm: dtsi: am335x-bone-common, usb0 is peripheral only
Date: Thu, 13 Feb 2014 15:25:52 -0800	[thread overview]
Message-ID: <20140213232552.GR28216@atomide.com> (raw)
In-Reply-To: <20140213231333.GK31787@pengutronix.de>

* Markus Pargmann <mpa@pengutronix.de> [140213 15:16]:
> Hi,
> 
> On Thu, Feb 13, 2014 at 02:54:38PM -0800, Tony Lindgren wrote:
> > * Markus Pargmann <mpa@pengutronix.de> [140111 06:03]:
> > > The PMIC is using usb0 vbus line as power source. It is also connected
> > > to the am335x processor as vbus sense. But there is no possibility to
> > > pullup usb0 vbus to operate as host. This patch fixes the dr_mode of usb0.
> > 
> > That's the MUSB? AFAIK it's not possible to operate MUSB in peripheral
> > only mode because the hardware does what it wants based on the ID
> > pin state.
> 
> Yes that's MUSB. The am335x reference manual describes that it is
> possible to force peripheral/host mode by setting bit 7 (IDDIG_MUX) in
> register USBnMODE to 1. Then it uses the bit written in bit 8 (IDDIG) of
> register USBnMODE to set host/peripheral mode.

OK
 
> I am not sure if the driver supports it yet but I think the DTS should
> contain the correct mode nevertheless, especially to avoid starting the
> otg loops in the musb driver.

Well there's one more thing to consider.. I think in the OTG role change
case the VBUS is still driven externally from the original host, so the
lack of VBUS does not always mean that host mode should be disabled.

Regards,

Tony

  reply	other threads:[~2014-02-13 23:26 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-01-11 14:00 [PATCH] arm: dtsi: am335x-bone-common, usb0 is peripheral only Markus Pargmann
2014-01-11 14:00 ` Markus Pargmann
2014-02-13 22:54 ` Tony Lindgren
2014-02-13 22:54   ` Tony Lindgren
2014-02-13 23:13   ` Markus Pargmann
2014-02-13 23:13     ` Markus Pargmann
2014-02-13 23:25     ` Tony Lindgren [this message]
2014-02-13 23:25       ` Tony Lindgren
2014-02-14 10:02       ` Markus Pargmann
2014-02-14 10:02         ` Markus Pargmann
2014-02-14 16:20         ` Tony Lindgren
2014-02-14 16:20           ` Tony Lindgren

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