Re: [PATCH] ARM: Samsung: Select ARM_CPU_SUSPEND when required

[Sylwester Nawrocki <s.nawrocki@samsung.com>]

On 04/08/2013 01:00 PM, Russell King - ARM Linux wrote:
> On Mon, Apr 08, 2013 at 12:27:34PM +0200, Sylwester Nawrocki wrote:
>> On 04/08/2013 11:57 AM, Kukjin Kim wrote:
[...]
> 
> Sigh.  This stuff looks rather screwed up now:
> 
> $ grep -B1 'ENTRY.*do_suspend' arch/arm/mm/proc*.S
> arch/arm/mm/proc-arm920.S-#ifdef CONFIG_PM_SLEEP
> arch/arm/mm/proc-arm920.S:ENTRY(cpu_arm920_do_suspend)
> --
> arch/arm/mm/proc-arm926.S-#ifdef CONFIG_PM_SLEEP
> arch/arm/mm/proc-arm926.S:ENTRY(cpu_arm926_do_suspend)
> --
> arch/arm/mm/proc-mohawk.S-#ifdef CONFIG_PM_SLEEP
> arch/arm/mm/proc-mohawk.S:ENTRY(cpu_mohawk_do_suspend)
> --
> arch/arm/mm/proc-sa1100.S-#ifdef CONFIG_PM_SLEEP
> arch/arm/mm/proc-sa1100.S:ENTRY(cpu_sa1100_do_suspend)
> --
> arch/arm/mm/proc-v6.S-#ifdef CONFIG_PM_SLEEP
> arch/arm/mm/proc-v6.S:ENTRY(cpu_v6_do_suspend)
> --
> arch/arm/mm/proc-v7.S-#ifdef CONFIG_ARM_CPU_SUSPEND
> arch/arm/mm/proc-v7.S:ENTRY(cpu_v7_do_suspend)
> --
> arch/arm/mm/proc-xsc3.S-#ifdef CONFIG_PM_SLEEP
> arch/arm/mm/proc-xsc3.S:ENTRY(cpu_xsc3_do_suspend)
> --
> arch/arm/mm/proc-xscale.S-#ifdef CONFIG_PM_SLEEP
> arch/arm/mm/proc-xscale.S:ENTRY(cpu_xscale_do_suspend)
> 
> Now, CONFIG_PM_SLEEP is fine if this stuff only ever gets used when PM_SLEEP
> is enabled - that's what it was designed for in the first place.  However,
> as we can see from the earlier patches in this thread, the cpu_suspend
> stuff is being selected when PM is enabled (which is arguably wrong), and

Yes, presumably this needs to be cleaned up. I was considering replacing
CONFIG_PM with CONFIG_PM_SLEEP, but that might involve some not trivial
changes. I'm going to have a look at it eventually.

> also in some cases when CPU_IDLE is enabled.
> 
> Therefore, making this code depend on ARM_CPU_SUSPEND seems sensible.
> However, So, how did proc-v7.S and only that file end up doing something
> different?
> 
> commit 15e0d9e37c7fe9711b60f47221c394d45553ad8c
> Author: Arnd Bergmann <arnd@arndb.de>
> Date:   Sat Oct 1 21:09:39 2011 +0200
> 
>     ARM: pm: let platforms select cpu_suspend support
> 
>     Support for the cpu_suspend functions is only built-in
>     when CONFIG_PM_SLEEP is enabled, but omap3/4, exynos4
>     and pxa always call cpu_suspend when CONFIG_PM is enabled.
> 
>     Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> 
> ...
> diff --git a/arch/arm/mm/proc-v7.S b/arch/arm/mm/proc-v7.S
> index a30e785..591accd 100644
> --- a/arch/arm/mm/proc-v7.S
> +++ b/arch/arm/mm/proc-v7.S
> @@ -217,7 +217,7 @@ ENDPROC(cpu_v7_set_pte_ext)
>  /* Suspend/resume support: derived from arch/arm/mach-s5pv210/sleep.S */
>  .globl cpu_v7_suspend_size
>  .equ   cpu_v7_suspend_size, 4 * 9
> -#ifdef CONFIG_PM_SLEEP
> +#ifdef CONFIG_ARM_CPU_SUSPEND
>  ENTRY(cpu_v7_do_suspend)
> ...
> 
> As far as this commit goes, it looks sane at the time that it was written,
> but as soon as we have *any* other selections of ARM_CPU_SUSPEND, the
> whole idea becomes extremely fragile - hence the reason for your build
> errors.
> 
> Moreover, with the above commit, there is _no_ sense what so ever in not
> applying the same change to all proc-*.S files, thereby entirely avoiding
> this fragility.  I would argue that the original commit should have made
> the same change to _all_ proc-*.S files.
> 
> Let's do the job properly - hence this is now queued for -rc:

Thanks, that seems a most reasonable fix. I was considering something like
that, just was afraid a bit to do this wide change and that it might cause
some other issues. Anyway that looks fine.

> 8<===
> From: Russell King <rmk+kernel@arm.linux.org.uk>
> Subject: [PATCH] ARM: Do 15e0d9e37c (ARM: pm: let platforms select cpu_suspend support) properly
> 
> Let's do the changes properly and fix the same problem everywhere, not
> just for one case.
> 
> Cc: <stable@vger.kernel.org> # kernels containing 15e0d9e37c7fe or equivalent
> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
> ---
>  arch/arm/mm/proc-arm920.S |    2 +-
>  arch/arm/mm/proc-arm926.S |    2 +-
>  arch/arm/mm/proc-mohawk.S |    2 +-
>  arch/arm/mm/proc-sa1100.S |    2 +-
>  arch/arm/mm/proc-v6.S     |    2 +-
>  arch/arm/mm/proc-xsc3.S   |    2 +-
>  arch/arm/mm/proc-xscale.S |    2 +-
>  7 files changed, 7 insertions(+), 7 deletions(-)
> 
> diff --git a/arch/arm/mm/proc-arm920.S b/arch/arm/mm/proc-arm920.S
> index 2c3b942..2556cf1 100644
> --- a/arch/arm/mm/proc-arm920.S
> +++ b/arch/arm/mm/proc-arm920.S
> @@ -387,7 +387,7 @@ ENTRY(cpu_arm920_set_pte_ext)
>  /* Suspend/resume support: taken from arch/arm/plat-s3c24xx/sleep.S */
>  .globl	cpu_arm920_suspend_size
>  .equ	cpu_arm920_suspend_size, 4 * 3
> -#ifdef CONFIG_PM_SLEEP
> +#ifdef CONFIG_ARM_CPU_SUSPEND
>  ENTRY(cpu_arm920_do_suspend)
>  	stmfd	sp!, {r4 - r6, lr}
>  	mrc	p15, 0, r4, c13, c0, 0	@ PID
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