On 03/10/2014 12:22 PM, Mark Brown wrote: > On Mon, Mar 10, 2014 at 12:11:44PM -0500, Nishanth Menon wrote: >> On 03/02/2014 09:54 PM, Mark Brown wrote: >>> On Mon, Feb 24, 2014 at 08:38:07AM -0600, Nishanth Menon wrote: > >>>> Intent here is to allow drivers such as cpufreq-cpu0 to be reused on >>>> platforms such as TI's OMAP derivatives, and other SoCs which differ >>>> only by the sequence involved in voltage scale operations. So, this >>>> patch provides a framework for registering the underlying >>>> implementation of the SoC specific voltage change methodology. > >>> That bit is clear, what's very opaque from the code is how this is going >>> to be accomplished. > >> The SoC specific voltage domain drivers register with >> devm_voltdm_register. the fops provide the abstraction needed for the >> SoC (example in patch #5 - which introduces OMAP specific voltage >> domain which handles ABB and VDD regulators). > >> What would you suggest that we do to clarify the usage here? > > Probably saying something about this in the commit message would be > enough - mentioning how the registration occurs and that things are > triggered by clock frequency changes. OK. will do, thanks for suggesting the same. >>> So the first question I have here is what happens if multiple clocks >>> need to be updated in lock step - if we're only triggering off clock >>> notifiers that seems tricky. The other thing here is that the fact that > >> Yes, that is true, however, there are ways to implement them, for >> example: We could implement an higher level clock that takes care of >> the multiple clock node control to handle this kind of scenario. > > That seems concerning given the fact that people seem to like describing > their entire clock trees in DT, we shouldn't be putting implementation > stuff there. The only other options are: a) Abstract it at a higher level at "user drivers", since they are aware of the sequencing needs - but this partially defeats the purpose, unless ofcourse, we do a tricky implementation such as: clk a, b, c -> prenotifiers in a, postnotifiers in c (which as you mentioned is a little trickier to get right). b) introduce a higher level generic dvfs function[1] which does not seem very attractive either. Any other suggestions other than limiting the usage(and documenting it so) and hoping for a future evolution to take this into consideration? [1] http://marc.info/?t=139275581900004&r=1&w=2 -- Regards, Nishanth Menon -- 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
