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

Nigel Cunningham
2009-04-19T23:31:47Z

Hi.

On Sat, 2009-04-18 at 20:47 +0200, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rjw@sisk.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@sisk.pl>
> Reported-by: Russell King <rmk+kernel@arm.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@tuxonice.net>

Regards,

Nigel