linux-kernel - Re: [RFC PATCH 0/6] Suspend USB Host controller on bus suspend

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Date:	Thu, 20 Jun 2013 13:19:31 -0400 (EDT)
From:	Alan Stern <stern@...land.harvard.edu>
To:	Roger Quadros <rogerq@...com>
cc:	tony@...mide.com, <balbi@...com>, <ruslan.bilovol@...com>,
	<linux-usb@...r.kernel.org>, <linux-omap@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [RFC PATCH 0/6] Suspend USB Host controller on bus suspend

On Thu, 20 Jun 2013, Roger Quadros wrote:

> >> As the omap-ehci controller driver needs to do some additional work to put
> >> itself into suspend/resume and make sure it is resumed to process an interrupt,
> >> we need to be able to override irq, bus_suspend, and bus_resume handlers. This
> >> provision is done in patch 3.
> > 
> > Do you still need to override these things if you do the controller
> > suspend at the right time?
> > 
> 
> At least not for bus_suspend and bus_resume. We will still need to override the irq
> handler though. But, if we can take care of this generically in the ehci_irq handler (i.e. make
> sure controller is not suspended while accessing it) then we don't need such override
> for irq.

I don't think you need to override anything.  The high-level interrupt
handler usb_hcd_irq() will avoid calling ehci_irq() when the
HCD_HW_ACCESSIBLE flag isn't set.  All you will need to do in
ehci-omap.c is call synchronize_irq() after ehci_suspend() returns and
before turning off the clocks.

Alan Stern

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