linux-kernel - RE: [PATCH 6/6 v2] arm: omap: usb: global Suspend and resume support of ehci and ohci

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Date:	Tue, 5 Jul 2011 10:22:09 -0400 (EDT)
From:	Alan Stern <stern@...land.harvard.edu>
To:	Partha Basak <p-basak2@...com>
cc:	Keshava Munegowda <keshava_mgowda@...com>,
	<linux-usb@...r.kernel.org>, <linux-omap@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, Felipe Balbi <balbi@...com>,
	Anand Gadiyar <gadiyar@...com>, <sameo@...ux.intel.com>,
	<parthab@...ia.ti.com>, <tony@...mide.com>,
	Kevin Hilman <khilman@...com>,
	Benoit Cousson <b-cousson@...com>, <paul@...an.com>,
	<johnstul@...ibm.com>, Vishwanath Sripathy <vishwanath.bs@...com>
Subject: RE: [PATCH 6/6 v2] arm: omap: usb: global Suspend and resume support
 of ehci and ohci

On Tue, 5 Jul 2011, Partha Basak wrote:

> >> Note that the parent per-se does not have any .suspend & .resume
> >hooked
> >> up.
> >
> >Why not?  That sounds like a big bug.
> 
> This was a design decision since the parent needs to be activated only
> when at-least one child is insmoded.
> 
> If the chidren are suspended, automatically the parent is suspended
> via the pm_runtime_putsync calls to the parent.

Now you know that this isn't true, because those calls don't get made 
while a system sleep transition is in progress.

> So, effectively, we do not need an explicit suspend for the parent.

Now you know that effectively you _do_ need an explicit suspend for the 
parent.

> >You have ignored a few very important points:
> >
> >Firstly, system suspend is supposed to work even when runtime PM is not
> >configured.
> >
> >Secondly, the user can disable runtime PM via sysfs at any time.  This
> >shouldn't mess up system suspend.
> >
> >Basically, it's a bad idea to mix up system suspend with runtime PM.
> 
> Your observations are correct but this is a generic limitation and Kevin
> is working
> on this problem in parallel.
> 
> As of now, all OMAP drivers are mandated to use ONLY runtime pm framework
> for enabling/disabling clocks. I will let Kevin comment further.

Okay, let's see what Kevin says.

Alan Stern

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