Handling device shared SFR on dt platform

On Wed, 04 Apr 2012 22:35:50 +0200, Sylwester Nawrocki [off-list ref] wrote:

On 04/03/2012 06:04 PM, Grant Likely wrote:

quoted

quoted

What concerns me, is an overhead from region request/ioremap(?)/release, 
just to access a single 32-bit register. I'm going to see if those accesses
could be moved to only device driver's probe() and remove() callbacks and 
what might be the resulting power consumption increase from that, if any.

Personally, I'd just create a shared function used by both drivers to
access the register and protect it with a spinlock.  That way the
region only needs to be mapped once, and the overhead is as low as
possible.

Hmm, that's what I originally started with. I've just removed function 
callback from the platform data struct in favour of having the drivers 
using directly the function exported by plat-s5p. Then I started devising
something alternative, in hope to get rid of the drivers compilation 
dependency on PLAT_S5P. There seems little point in that though, since 
the chance to have those IP blocks available on other archs or ARM sub-archs,
than Samsung S5P/Exynos, are extremely low. 

As long as everything remains multiplatform friendly, I'm fine with
this.  It will need to change though if ever there needs to be
multiple definitions of that helper function because that means only
one platform can be enabled at a time.

g.