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SubjectRe: [PATCH] ARM: suspend: use flush range instead of flush all
+ Lorenzo,

On Wed, Sep 12, 2012 at 12:48 PM, wzch <wzch@marvell.com> wrote:
> From: Wenzeng Chen <wzch@marvell.com>
>
> In cpu suspend function __cpu_suspend_save(), we save cp15 registers,
> resume function, sp and suspend_pgd, then flush the data to DDR, but
> no need to flush all D cache, only need to flush range.
>
> Change-Id: I591a1fde929f3f987c69306b601843ed975d3e41
You should drop above.

> Signed-off-by: Wenzeng Chen <wzch@marvell.com>
> ---
Lorenzo and myself discussed about the above expensive flush and he
is planning to post a similar patch but with small difference.

> arch/arm/kernel/suspend.c | 4 +++-
> 1 files changed, 3 insertions(+), 1 deletions(-)
>
> diff --git a/arch/arm/kernel/suspend.c b/arch/arm/kernel/suspend.c
> index 1794cc3..bb582d8 100644
> --- a/arch/arm/kernel/suspend.c
> +++ b/arch/arm/kernel/suspend.c
> @@ -17,6 +17,7 @@ extern void cpu_resume_mmu(void);
> */
> void __cpu_suspend_save(u32 *ptr, u32 ptrsz, u32 sp, u32 *save_ptr)
> {
> + u32 *ptr_orig = ptr;
> *save_ptr = virt_to_phys(ptr);
>
> /* This must correspond to the LDM in cpu_resume() assembly */
> @@ -26,7 +27,8 @@ void __cpu_suspend_save(u32 *ptr, u32 ptrsz, u32 sp, u32 *save_ptr)
>
> cpu_do_suspend(ptr);
>
> - flush_cache_all();
Lorenzo's patch was limiting above flush to local cache (LOUs) instead
of dropping
it completely.

> + __cpuc_flush_dcache_area((void *)ptr_orig, ptrsz);
> + __cpuc_flush_dcache_area((void *)save_ptr, sizeof(*save_ptr));
> outer_clean_range(*save_ptr, *save_ptr + ptrsz);
> outer_clean_range(virt_to_phys(save_ptr),
> virt_to_phys(save_ptr) + sizeof(*save_ptr));

Just thinking bit more, even in case we drop the flush_cache_all()
completely, it should be safe since the suspend_finisher() takes
care of the cache maintenance already.

Regards
Santosh


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