On 03/15/2013 06:33 AM, Ulf Hansson wrote: > On 15 March 2013 13:06, Bill Huang <bilhu...@nvidia.com> wrote: >> On Fri, 2013-03-15 at 18:08 +0800, Ulf Hansson wrote: ... >>> Some prerequisites; I think am in favor of using the clk API to >>> trigger DVFS changes and then I agree on that clk_prepare|unprepare >>> needs to be possible to track from a DVFS perspective. clk_set_rate is >>> not enough. >>> >>> So if we decide to do the above (using the clk API to trigger DVFS >>> changes), I believe we should discuss two possible solutions; >>> - clk notifiers or.. >>> - dvfs clock type. >>> >>> I am trying to make up my mind of what I think is the best solution. >>> Have you considered "dvfs clock type"? >>> I put some comments about this for "[PATCH 2/5] clk: notifier handler >>> for dynamic voltage scaling" recently as well. >>> >>> What could the advantages/disadvantages be between the two options? >> >> I personally prefer clk notifiers since that's easy and all the existing >> device drivers don't need to be modified, a new clock or API might be >> more thoroughly considered (and hence maybe more graceful) but that >> means we need more time to cook and many drivers need to plug into that >> API when it comes out, a lot of test/verification or maybe chaos >> follows, I'm not sure will that be a little overkill. > > I guess you did not fully got what I meant with "dvfs clock type". It > will not affect the clock API. But instead the dvfs is handled by > implementing a specific clk hw type. So the same thing is accomplished > as with clk notifiers, no changes should be needed to device drivers. > > The difference is only that no notifiers will be needed, and all the > dvfs stuff will be handled in the clk hw instead. It will mean that we > will bundle dvfs stuff into the clock drivers, instead of separating > the code outside the clock drivers. But, on the other hand no > notifiers will be needed.
The advantage here is that I assume that a notifier would continually have to check whether the clock being modified was one that the DVFS notifier cared about. By integrating the CVFS logic into the clk_hw itself, it'll only ever get executed for clocks that really care about DVFS. Presumably, the code that implements the clk_hw could also use some common DVFS library as part of the implementation, and still share code. Or perhaps, what about putting DVFS "ops" into a clk_hw alongside any other existing ops, and having the clock core call them whenever appropriate? _______________________________________________ linaro-dev mailing list linaro-dev@lists.linaro.org http://lists.linaro.org/mailman/listinfo/linaro-dev