On Wed, Apr 29, 2015 at 3:40 AM, Mark Brown <broonie@xxxxxxxxxx> wrote: > On Tue, Apr 28, 2015 at 09:58:48PM -0700, Kevin Cernekee wrote: >> On Sat, Apr 25, 2015 at 4:32 AM, Mark Brown <broonie@xxxxxxxxxx> wrote: > >> > What we should be doing here is providing a way for users to tell regmap >> > if they've reset the register map and actually we already have that >> > interface, it's just not got the best name - regcache_mark_dirty() is >> > effectively it since there's really not a lot of other reasons why a >> > driver would need to mark the cache as dirty. We're just not handling > >> 1) How do we tell the difference between "regcache contains a >> non-default value that correctly reflects the hardware register >> contents" versus "regcache contains a non-default value that is >> waiting to be written when we exit cache_only mode"? > > Like I said above we can tell if the hardware was reset because > mark_dirty() is called. That covers the public API, but I do not understand how you intended for this data to be stored in the rbtree if the use of a dirty bitmask is discouraged. i.e. regcache_sync() finds a register value marked "present". How do we know whether we need to write it back to the hardware? For the special case of "cached non default register values immediately after a HW reset" you can mostly figure this out, but if there was no HW reset how do we know which entries changed while the HW was inaccessible? > I'm not suggesting that we do anything based on the presence of a cache > entry, I'm suggesting that we could avoid having to ever cache values > that never get referenced on a system (which can be a lot of them for > common use cases) saving us memory. This seems to be solving a different problem. It sounds like you are more worried about regcache_sync() writing back lots of default values for registers that were never touched, than performing unnecessary writes to a few (actively used) registers that weren't changed while we were in cache_only mode. Is that accurate? FWIW, in the current iteration of the tas571x driver, there are few if any registers that meet this criteria. -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
