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

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Date:	Tue, 18 Jun 2013 11:18:49 -0400 (EDT)
From:	Alan Stern <stern@...land.harvard.edu>
To:	Felipe Balbi <balbi@...com>
cc:	Roger Quadros <rogerq@...com>, Chao Xie <chao.xie@...vell.com>,
	<gregkh@...uxfoundation.org>, <linux-usb@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>, <xiechao.mail@...il.com>
Subject: Re: [PATCH] USB: initialize or shutdown PHY when add or remove host
 controller

On Tue, 18 Jun 2013, Felipe Balbi wrote:

> yeah, Roger brought up a big problem with OMAP's EHCI depending on the
> mode so, at least for now, we should keep phy_get and, in case of EHCI
> OMAP, phy_init in the glue :-(
> 
> Roger has all the details, and they're also in the list archives, but
> basically, depending on the mode, PHY *must* be initialized at a
> particular point.

Right.  Which means the core shouldn't be involved, since the OMAP PHY
initialization has to be done at a non-standard time.  (Unless we 
decide to add a flag for this special case...)

> > Given that the glue module has to be responsible for getting the PHY,
> > it should also be responsible for error checking.  So the code added to
> > hcd.c doesn't need to apply an IS_ERR check; it can simply assume that
> > if hcd->phy is NULL then either there is no software-controllable PHY
> > or else the HCD doesn't want the core to manage it.
> 
> makes sense to me, add the requirement to:
> 
> if (IS_ERR(hcd->phy))
> 	hcd->phy = NULL;

Actually, in the IS_ERR case, most glue drivers just fail the probe.  
But for any that want to continue on, we would have to add this
requirement.

Alan Stern

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