linux-kernel - Re: [PATCH v2 3/8] core: platform: wakeup the parent before trying any driver operations

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Date:	Mon, 25 May 2015 13:36:43 -0400 (EDT)
From:	Alan Stern <stern@...land.harvard.edu>
To:	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
cc:	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	<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>
Subject: Re: [PATCH v2 3/8] core: platform: wakeup the parent before trying
 any driver operations

On Mon, 25 May 2015, Andy Shevchenko wrote:

> From: Heikki Krogerus <heikki.krogerus@...ux.intel.com>
> 
> If the parent is still suspended when a driver probe,
> remove or shutdown is attempted, the result may be a
> 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 using driver probe, remove or shutdown.
> 
> Signed-off-by: Heikki Krogerus <heikki.krogerus@...ux.intel.com>
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
> ---
>  drivers/base/platform.c | 21 ++++++++++++++++++++-

Why make the changes here rather than in dd.c?  Is there something 
special about platform devices?

Alan Stern

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