[PATCH 06/14] ARM: suspend: rejig suspend follow-on function calling convention

[robherring2@gmail.com (Rob Herring)]

Russell,

On 06/13/2011 12:16 PM, Russell King - ARM Linux wrote:
> Save the suspend function pointer onto the stack for use when returning.
> Allocate r2 to pass an argument to the suspend function.
> 
> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
> ---
>  arch/arm/kernel/sleep.S |    9 +++++----
>  1 files changed, 5 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/arm/kernel/sleep.S b/arch/arm/kernel/sleep.S
> index 358be13..b924bcc 100644
> --- a/arch/arm/kernel/sleep.S
> +++ b/arch/arm/kernel/sleep.S
> @@ -10,6 +10,7 @@
>  /*
>   * Save CPU state for a suspend
>   *  r1 = v:p offset
> + *  r2 = suspend function arg0
>   *  r3 = virtual return function
>   * Note: sp is decremented to allocate space for CPU state on stack
>   * r0-r3,ip,lr corrupted
> @@ -17,7 +18,6 @@
>  ENTRY(cpu_suspend)
>  	stmfd	sp!, {r3}
>  	stmfd	sp!, {r4 - r11}
> -	mov	r9, lr
>  #ifdef MULTI_CPU
>  	ldr	r10, =processor
>  	ldr	r5, [r10, #CPU_SLEEP_SIZE] @ size of CPU sleep state
> @@ -33,6 +33,7 @@ ENTRY(cpu_suspend)
>  	stmfd	sp!, {r1, r6, ip}	@ save v:p, virt SP, phys resume fn
>  	ldr	r5, =sleep_save_sp
>  	add	r6, sp, r1		@ convert SP to phys
> +	stmfd	sp!, {r2, lr}		@ save suspend func arg and pointer
>  #ifdef CONFIG_SMP
>  	ALT_SMP(mrc p15, 0, lr, c0, c0, 5)
>  	ALT_UP(mov lr, #0)
> @@ -51,12 +52,12 @@ ENTRY(cpu_suspend)
>  	@ flush data cache
>  #ifdef MULTI_CACHE
>  	ldr	r10, =cpu_cache
> -	mov	lr, r9
> +	mov	lr, pc
>  	ldr	pc, [r10, #CACHE_FLUSH_KERN_ALL]
>  #else
> -	mov	lr, r9
> -	b	__cpuc_flush_kern_all
> +	bl	__cpuc_flush_kern_all
>  #endif

If you change:

> +	ldmfd	sp!, {r0, pc}		@ call suspend fn

To:
	mov	lr, pc
	ldmfd	sp!, {r0, pc}
	ldmfd	sp!, {r1, r6, ip}
	mov	sp, r6
	ldmfd	sp!, {r4-r11, pc}

It will allow the suspend fn to return and abort suspend. With that, I'm
able to use this for core powerdown in cpuidle.

Rob