[RFC PATCH v2 3/5] ARM: kernel: update cpu_suspend code to use cache LoUIS operations

[will.deacon@arm.com (Will Deacon)]

On Tue, Dec 11, 2012 at 04:07:56PM +0000, Guennadi Liakhovetski wrote:
> Hi all
> 
> On Thu, 20 Sep 2012, Dave Martin wrote:
> 
> > On Thu, Sep 20, 2012 at 11:25:14AM +0100, Lorenzo Pieralisi wrote:
> > > On Wed, Sep 19, 2012 at 02:46:58PM +0100, Dave Martin wrote:
> > > > On Tue, Sep 18, 2012 at 05:35:33PM +0100, Lorenzo Pieralisi wrote:
> > > > > In processors like A15/A7 L2 cache is unified and integrated within the
> > > > > processor cache hierarchy, so that it is not considered an outer cache
> > > > > anymore. For processors like A15/A7 flush_cache_all() ends up cleaning
> > > > > all cache levels up to Level of Coherency (LoC) that includes
> > > > > the L2 unified cache.
> > > > > 
> > > > > When a single CPU is suspended (CPU idle) a complete L2 clean is not
> > > > > required, so generic cpu_suspend code must clean the data cache using the
> > > > > newly introduced cache LoUIS function.
> 
> Git bisect identified this patch, in the mainline as
> 
> commit dbee0c6fb4c1269b2dfc8b0b7a29907ea7fed560
> Author: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
> Date:   Fri Sep 7 11:06:57 2012 +0530
> 
>     ARM: kernel: update cpu_suspend code to use cache LoUIS operations
> 
> as the culprit of the broken wake up from STR on mackerel, based on an 
> sh7372 A8 SoC. .config attached.

My guess is that because Cortex-A8 does not implement the MP extensions,
the LoUIS field of the CLIDR reads as zero, and the cache isn't flushed at
all (I can see an early exit in v7_flush_dcache_louis).

Lorenzo -- how is this supposed to work for uniprocessor CPUs?

Will