From mboxrd@z Thu Jan  1 00:00:00 1970
From: s.hauer@pengutronix.de (Sascha Hauer)
Date: Tue, 17 Apr 2012 14:18:00 +0200
Subject: [RFC PATCH 0/8] MXS: Add i.MX28 USB Host driver
In-Reply-To: <201204171345.07851.marex@denx.de>
References: <1334657751-27678-1-git-send-email-marex@denx.de>
 <20120417112910.GA3852@pengutronix.de>
 <201204171345.07851.marex@denx.de>
Message-ID: <20120417121800.GB3852@pengutronix.de>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

On Tue, Apr 17, 2012 at 01:45:07PM +0200, Marek Vasut wrote:
> Dear Sascha Hauer,
> 
> > Hi Marek,
> > 
> > On Tue, Apr 17, 2012 at 12:15:43PM +0200, Marek Vasut wrote:
> > > This patchset introduces the USB Host driver for i.MX28 CPU, utilising
> > > the generic USB PHY infrastructure.
> > 
> > Your patches won't work when more than one USB port is enabled because
> > of the singular usb transceiver present in the kernel. That of course is
> > not your fault. I think Heikki (Added to Cc) is working on this issue,
> > but I don't know the status here.
> 
> All right, I'll let Heikki hack on that. I'm not sure if we have any mx28 based 
> device with multiple USB ports in kernel. Do we ?
> 
> > Another problem is that what you are doing does not integrate at all
> > with otg.
> 
> Well, how should this be done to integrate with OTG then?
> 
> > I don't ask you to implement otg support because you are
> > likely not interested in this, but since you are adding a new ehci
> > glue driver anyway I suggest another approach:
> > 
> > Put a driver under drivers/usb/otg which:
> > 
> > - matches a 'imx-usb' device
> > - gets/enables all clocks needed for USB
> > - finds the transceiver
> > - registers a ehci device
> 
> So the PHY actually registers the EHCI driver (plat_bus->phy->ehci)? That's 
> slightly weird, don't you think?

Your hardware device is a device consisting of a ehci core and a USB device
core. Currently we register the child devices independently which leads
to the mentioned problems. Instead we should register the USB core as a
whole and pass the resources to either the client or the host driver.

The phys are completely independent devices (from a bus topology point
of view). The USB core just happens to use the phys.

Sascha

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