linux-kernel - Re: [PATCH V2] USB: initialize or shutdown PHY when add or remove host controller

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Message-ID: <20130624193643.GC11815@arwen.pp.htv.fi>
Date:	Mon, 24 Jun 2013 22:36:43 +0300
From:	Felipe Balbi <balbi@...com>
To:	Alan Stern <stern@...land.harvard.edu>
CC:	Felipe Balbi <balbi@...com>, Chao Xie <xiechao.mail@...il.com>,
	Roger Quadros <rogerq@...com>, Chao Xie <chao.xie@...vell.com>,
	Greg KH <gregkh@...uxfoundation.org>,
	"linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH V2] USB: initialize or shutdown PHY when add or remove
 host controller

On Thu, Jun 20, 2013 at 01:25:31PM -0400, Alan Stern wrote:
> On Thu, 20 Jun 2013, Felipe Balbi wrote:
> 
> > > In fact, the PHY setting and handling is related to platform or SOC,
> > > and for different SOC they can
> > > have same EHCI HCD but they PHY handling can be different.
> > > Omap'a case is the example, and i think some other vendors may have
> > > silimar cases.
> > > From above point, It is better to leave the PHY initialization and
> > > shutdown to be done by each echi-xxx driver.
> > > 
> > > So Alan and Felipe
> > > What are your ideas about it?
> > 
> > If we have so many exceptions, then sure. But eventually, the common
> > case should be added generically with a flag so that non-generic cases
> > (like OMAP) can request to handle the PHY by themselves.
> > 
> > Alan ?
> 
> I don't have very strong feelings about this; Felipe has much more
> experience with these things.
> 
> However, when the common case is added into the core, the simplest way
> to indicate that the HCD wants to handle the PHY(s) by itself will be
> to leave hcd->phy set to NULL or an ERR_PTR value.
> 
> One important thing that hasn't been pointed out yet: When we move
> these calls into the core, the same patch must also remove those calls
> from the glue drivers that currently do set hcd->phy.  And it must make
> sure that the glue drivers which handle the PHY by themselves do not
> set hcd->phy.

perfect summary. Perhaps Roger could already work on private PHY handle
for ehci-omap.c and later we can start moving generic case to usbcore
without having to touch ehci-omap.c at all. Roger, any commetns ?

-- 
balbi

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