linux-kernel - Re: [PATCH v3 3/8] Driver core: wakeup the parent device before trying probe

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Date:	Wed, 10 Jun 2015 17:02:21 +0300
From:	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:	"Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:	linux-acpi@...r.kernel.org, linux-pm@...r.kernel.org,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Vinod Koul <vinod.koul@...el.com>,
	Lee Jones <lee.jones@...aro.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Mika Westerberg <mika.westerberg@...ux.intel.com>,
	linux-kernel@...r.kernel.org, dmaengine@...r.kernel.org,
	Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
	Jarkko Nikula <jarkko.nikula@...ux.intel.com>,
	"Wysocki, Rafael J" <rafael.j.wysocki@...el.com>,
	Mike Turquette <mturquette@...aro.org>
Subject: Re: [PATCH v3 3/8] Driver core: wakeup the parent device before
 trying probe

On Wed, 2015-06-10 at 02:08 +0200, Rafael J. Wysocki wrote: 
> On Tuesday, June 09, 2015 01:42:00 AM Rafael J. Wysocki wrote:
> > On Monday, June 01, 2015 05:47:57 PM Andy Shevchenko wrote:
> > > From: Heikki Krogerus <heikki.krogerus@...ux.intel.com>
> > > 
> > > If the parent is still suspended when driver probe is
> > > attempted, the result may be failure.
> > > 
> > > For example, if the parent is a PCI MFD device that has been
> > > suspended when we try to probe our device, any register
> > > reads will return 0xffffffff.
> > > 
> > > To fix the problem, making sure the parent is always awake
> > > before attempting driver probe.

[]

> Actually, something like the below should work too (the bumping up of the
> parent's usage counter before the loop will keep it in the runtime-active
> state throughout the loop).

It works. Thanks for the patch. We incorporate it instead of the
previous Heikki's patch into v4.

-- 
Andy Shevchenko <andriy.shevchenko@...el.com>
Intel Finland Oy

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