linux-kernel - Re: [PATCH] ARM: suspend: use flush range instead of flush all

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Message-ID: <20120912085445.GW13739@n2100.arm.linux.org.uk>
Date:	Wed, 12 Sep 2012 09:54:45 +0100
From:	Russell King - ARM Linux <linux@....linux.org.uk>
To:	"Shilimkar, Santosh" <santosh.shilimkar@...com>
Cc:	wzch <wzch@...vell.com>, Dave Martin <dave.martin@...aro.org>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will.deacon@....com>,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	Lorenzo Pieralisi <lorenzo.pieralisi@....com>
Subject: Re: [PATCH] ARM: suspend: use flush range instead of flush all

On Wed, Sep 12, 2012 at 01:13:33PM +0530, Shilimkar, Santosh wrote:
> On Wed, Sep 12, 2012 at 12:48 PM, wzch <wzch@...vell.com> wrote:
> >  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.

Err, that is wrong.  Normally, when CPUs go into suspend, the L1 cache is
lost entirely.  This is the only flush which many CPUs see of the L1
cache.

So removing this flush _will_ break suspend to RAM on existing CPUs.
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