linux-kernel - Re: 900af0d breaks some embedded suspend/resume

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Message-Id: <200904190044.58444.rjw@sisk.pl>
Date:	Sun, 19 Apr 2009 00:44:57 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Russell King <rmk+lkml@....linux.org.uk>,
	Len Brown <lenb@...nel.org>,
	Linux Kernel List <linux-kernel@...r.kernel.org>,
	pm list <linux-pm@...ts.linux-foundation.org>,
	ACPI Devel Maling List <linux-acpi@...r.kernel.org>
Subject: Re: 900af0d breaks some embedded suspend/resume

On Saturday 18 April 2009, Linus Torvalds wrote:
> 
> On Sat, 18 Apr 2009, Russell King wrote:
> > 
> > What I need to be able to do is to suspend most devices on the host side
> > which may involve talking to a separate microcontroller via I2C to shut
> > down power to peripherals.
> 
> I suspect that for cases like this, the simplest thing to do is to just 
> add a marker for "don't mess with my power management, I'm doing 
> everything through sysdev" for the specified devices.

In this particular case, if sysdev was used, there would be no problem, but the
platform uses a platform device to suspend-resume the i2c controller.
In principle we could convert it to use a sysdev, but that would be more
difficult than the last patch I sent IMO (at least to me).

Also, apparently it is not the only platform doing it.

> Then those i2c controllers (and perhaps some PCI bridges etc) can just set 
> that bit, and the device would basically turn invisible as far as the PM 
> layer is concerned.
> 
> Not that different from the IRQF_TIMER bit for timer interrupts.

I generally agree and a patch to implemet such a flag has been submitted
recently.

Thanks,
Rafael
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