Re: [PATCH 2/6] ARM: pm: add generic CPU suspend/resume support

Colin Cross
2011-02-16T00:26:00Z

On Tue, Feb 15, 2011 at 3:04 AM, Russell King - ARM Linux
<linux@arm.linux.org.uk> wrote:
> On Fri, Feb 11, 2011 at 06:50:57PM -0800, Colin Cross wrote:
>> > +ENDPROC(cpu_resume_turn_mmu_on)
>> > +cpu_resume_after_mmu:
>> > +       str     r5, [r2, r4, lsl #2]    @ restore old mapping
>> > +#ifdef MULTI_CACHE
>> > +       ldr     r10, =cpu_cache
>> > +       ldr     pc, [r10, #CACHE_FLUSH_KERN_ALL]
>> > +#else
>> > +       b       __cpuc_flush_kern_all
>> > +#endif
>
> I think we can eliminate this cache flush by delaying the cache enable
> as below.  Could you see whether Tegra 2 survives this please?
> Thanks.
>
> diff --git a/arch/arm/kernel/sleep.S b/arch/arm/kernel/sleep.S
> index bed1876..193be5f 100644
> --- a/arch/arm/kernel/sleep.S
> +++ b/arch/arm/kernel/sleep.S
> @@ -4,6 +4,7 @@
>  #include <asm/assembler.h>
>  #include <asm/glue-cache.h>
>  #include <asm/glue-proc.h>
> +#include <asm/system.h>
>        .text
>
>  /*
> @@ -81,25 +82,22 @@ ENTRY(cpu_resume_mmu)
>        str     r3, [r2, r4, lsl #2]    @ setup 1:1 mapping for mmu code
>        sub     r2, r2, r1
>        ldr     r3, =cpu_resume_after_mmu
> +       bic     r1, r0, #CR_C           @ ensure D-cache is disabled
>        b       cpu_resume_turn_mmu_on
>  ENDPROC(cpu_resume_mmu)
>        .ltorg
>        .align  5
>  cpu_resume_turn_mmu_on:
> -       mcr     p15, 0, r0, c1, c0, 0   @ turn on MMU, caches, etc
> -       mrc     p15, 0, r0, c0, c0, 0   @ read id reg
> -       mov     r0, r0
> -       mov     r0, r0
> +       mcr     p15, 0, r1, c1, c0, 0   @ turn on MMU, I-cache, etc
> +       mrc     p15, 0, r1, c0, c0, 0   @ read id reg
> +       mov     r1, r1
> +       mov     r1, r1
>        mov     pc, r3                  @ jump to virtual address
>  ENDPROC(cpu_resume_turn_mmu_on)
>  cpu_resume_after_mmu:
>        str     r5, [r2, r4, lsl #2]    @ restore old mapping
> -#ifdef MULTI_CACHE
> -       ldr     r10, =cpu_cache
> -       ldr     pc, [r10, #CACHE_FLUSH_KERN_ALL]
> -#else
> -       b       __cpuc_flush_kern_all
> -#endif
> +       mcr     p15, 0, r0, c1, c0, 0   @ turn on D-cache
> +       mov     pc, lr
>
>  /*
>  * Note: Yes, part of the following code is located into the .data section.
>
>

Tested-by: Colin Cross <ccross@android.com>

Works for Tegra 2 cpuidle and suspend.