Handling device shared SFR on dt platform

[Sylwester Nawrocki]

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

I'll post finally some patches for review. Thank you.

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Regards,
Sylwester