linux-kernel - Re: [PATCH] PM/Suspend: Introduce two new platform callbacks to avoid breakage (Re: 900af0d breaks some embedded suspend/resume)

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Date:	Mon, 20 Apr 2009 09:31:47 +1000
From:	Nigel Cunningham <ncunningham-lkml@...a.org.au>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
Cc:	Russell King <rmk+lkml@....linux.org.uk>,
	Len Brown <lenb@...nel.org>,
	Linux Kernel List <linux-kernel@...r.kernel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	pm list <linux-pm@...ts.linux-foundation.org>,
	ACPI Devel Maling List <linux-acpi@...r.kernel.org>
Subject: Re: [PATCH] PM/Suspend: Introduce two new platform callbacks to
 avoid breakage (Re: 900af0d breaks some embedded suspend/resume)

Hi.

On Sat, 2009-04-18 at 20:47 +0200, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rjw@...k.pl>
> Subject: PM/Suspend: Introduce two new platform callbacks to avoid breakage
> 
> Commit 900af0d973856d6feb6fc088c2d0d3fde57707d3 (PM: Change suspend
> code ordering) changed the ordering of suspend code in such a way
> that the platform .prepare() callback is now executed after the
> device drivers' late suspend callbacks have run.  Unfortunately, this
> turns out to break ARM platforms that need to talk via I2C to power
> control devices during the .prepare() callback.
> 
> For this reason introduce two new platform suspend callbacks,
> .prepare_late() and .wake(), that will be called just prior to
> disabling non-boot CPUs and right after bringing them back on line,
> respectively, and use them instead of .prepare() and .finish() for
> ACPI suspend.  Make the PM core execute the .prepare() and .finish()
> platform suspend callbacks where they were executed previously (that
> is, right after calling the regular suspend methods provided by
> device drivers and right before executing their regular resume
> methods, respectively).
> 
> It is not necessary to make analogous changes to the hibernation
> code and data structures at the moment, because they are only used
> by ACPI platforms.
> 
> Signed-off-by: Rafael J. Wysocki <rjw@...k.pl>
> Reported-by: Russell King <rmk+kernel@....linux.org.uk>
> ---
>  drivers/acpi/sleep.c    |    8 ++++----
>  include/linux/suspend.h |   36 ++++++++++++++++++++++++++----------
>  kernel/power/main.c     |   24 +++++++++++++++++-------
>  3 files changed, 47 insertions(+), 21 deletions(-)
> 
> Index: linux-2.6/kernel/power/main.c
> ===================================================================
> --- linux-2.6.orig/kernel/power/main.c
> +++ linux-2.6/kernel/power/main.c
> @@ -291,20 +291,26 @@ static int suspend_enter(suspend_state_t
>  
>  	device_pm_lock();
>  
> +	if (suspend_ops->prepare) {
> +		error = suspend_ops->prepare();
> +		if (error)
> +			goto Done;
> +	}
> +
>  	error = device_power_down(PMSG_SUSPEND);
>  	if (error) {
>  		printk(KERN_ERR "PM: Some devices failed to power down\n");
> -		goto Done;
> +		goto Platfrom_finish;

s/Platfrom/Platform

Why retain the typo in multiple places?

>  	}
>  
> -	if (suspend_ops->prepare) {
> -		error = suspend_ops->prepare();
> +	if (suspend_ops->prepare_late) {
> +		error = suspend_ops->prepare_late();
>  		if (error)
>  			goto Power_up_devices;
>  	}

Doesn't this invalidate testing that's already been done? Drivers
implementing prepare() (arm omap1, pxa, omap2, s3c and powerpc mpc52xx
and lite5200) are now going to have it called pre device_power_down. Why
not call the new prepare() "prepare_early" and leave the current prepare
as it is in the place where it's already called?

The name is also very confusing. Prepare matches with Finish and
Prepare_late with wake. How about prepare and unprepare?

Reviewed-by: Nigel Cunningham <nigel@...onice.net>

Regards,

Nigel

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