[RFC PATCH v2 1/5] ARM: mm: implement LoUIS API for cache maintenance ops

[Lorenzo Pieralisi]

On Tue, Sep 18, 2012 at 07:12:52PM +0100, Nicolas Pitre wrote:
> On Tue, 18 Sep 2012, Lorenzo Pieralisi wrote:
> 
> > ARM v7 architecture introduced the concept of cache levels and related
> > control registers. New processors like A7 and A15 embed an L2 unified cache
> > controller that becomes part of the cache level hierarchy. Some operations in
> > the kernel like cpu_suspend and __cpu_disable do not require a flush of the
> > entire cache hierarchy to DRAM but just the cache levels belonging to the
> > Level of Unification Inner Shareable (LoUIS), which in most of ARM v7 systems
> > correspond to L1.
> >
> > The current cache flushing API used in cpu_suspend and __cpu_disable,
> > flush_cache_all(), ends up flushing the whole cache hierarchy since for
> > v7 it cleans and invalidates all cache levels up to Level of Coherency
> > (LoC) which cripples system performance when used in hot paths like hotplug
> > and cpuidle.
> >
> > Therefore a new kernel cache maintenance API must be added to cope with
> > latest ARM system requirements.
> >
> > This patch adds flush_cache_louis() to the ARM kernel cache maintenance API.
> >
> > This function cleans and invalidates all data cache levels up to the
> > Level of Unification Inner Shareable (LoUIS) and invalidates the instruction
> > cache for processors that support it (> v7).
> >
> > This patch also creates an alias of the cache LoUIS function to flush_kern_all
> > for all processor versions prior to v7, so that the current cache flushing
> > behaviour is unchanged for those processors.
> >
> > v7 cache maintenance code implements a cache LoUIS function that cleans and
> > invalidates the D-cache up to LoUIS and invalidates the I-cache, according
> > to the new API.
> >
> > Reviewed-by: Santosh Shilimkar <santosh.shilimkar at ti.com>
> > Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi at arm.com>
> 
> Reviewed-by: Nicolas Pitre <nico at linaro.org>

Thanks a lot for reviewing the series.

Lorenzo