linux-kernel - Re: [RFC PATCH 4/6] USB: ehci-omap: Suspend the controller during bus suspend

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Message-ID: <20130703131513.GH15056@arwen.pp.htv.fi>
Date:	Wed, 3 Jul 2013 16:15:13 +0300
From:	Felipe Balbi <balbi@...com>
To:	Roger Quadros <rogerq@...com>
CC:	<balbi@...com>, Alan Stern <stern@...land.harvard.edu>,
	<tony@...mide.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 4/6] USB: ehci-omap: Suspend the controller during
 bus suspend

On Wed, Jul 03, 2013 at 04:06:04PM +0300, Roger Quadros wrote:
> On 07/03/2013 03:57 PM, Felipe Balbi wrote:
> > Hi,
> > 
> > On Tue, Jul 02, 2013 at 01:17:58PM -0400, Alan Stern wrote:
> >> A PCI-based EHCI controller has two power sources: the core well (which
> >> is turned off during suspend) and the auxiliary well (which remains
> >> powered).  That's how remote wakeup works; it uses the auxiliary well.
> > 
> > This, kinda, matches what OMAP tries to do with pad wakeup. Just that
> > pad wakeup sits outside of the device itself. Perhaps we could look into
> > how PCI handles the aux well and take some inspiration from there.
> > 
> > Any pointers under drivers/pci/ would be great :-)
> > 
> From what I understood, auxiliary well is just a power source, and it keeps
> the EHCI controller powered even during suspend.
> 
> If that is true then it is different from our situation as we power down the
> EHCI controller completely.

right but our "auxiliary well" keeps PRCM powered which can wake EHCI up
;-)

What I'm saying is that from ehci-omap's perspective, there's very
little difference, specially since we route the wakeup through the same
IRQ line anyway. Perhaps we could take some inspiration from the PCI
land to make our hwmod/omap_device a little easier from driver
perspective.

Or maybe it doesn't make sense ;-)

-- 
balbi

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