On 15 March 2013 20:38, Stephen Warren <swar...@wwwdotorg.org> wrote: > 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?
Thanks for your comment Stephen. I agree to your reflections as well. It will probably be a more optimized solution going this direction and we don't have to add more "clk notifier code" to the clk API, which I guess is good. It would be interesting to get some input from some of the maintainers to this discussion as well, let's see. Kind regards Ulf Hansson _______________________________________________ linaro-dev mailing list linaro-dev@lists.linaro.org http://lists.linaro.org/mailman/listinfo/linaro-dev
