Quoting Maxime Coquelin (2014-03-21 07:09:26) > Hi Mike, > > On 03/21/2014 02:45 AM, Mike Turquette wrote: > > Quoting Sylwester Nawrocki (2014-03-20 05:42:33) > >> Hi Maxime, > >> > >> On 06/03/14 14:45, Maxime Coquelin wrote: > >>> Hi Sylwester, > >>> > >>> I like the principle of your implementation, but I have two questions: > >>> 1 - How can we manage PM with this solution, as the parent/rate will be > >>> set only once at probe time? > >>> 2 - How to set the parent of a parent clock (which can be shared with > >>> other devices)? Same question about the parent rates. > >> > >> Thanks for your feedback and apologies for late reply. > >> > >> IIUC your first concern is about a situation when clocks need to be > >> reconfigured upon each resume from system sleep or runtime PM resume ? > >> As I mentioned in v1 of the RFC I was considering having individual > >> drivers calling explicitly the clocks set up routine. Presumably this > >> would allow to resolve the power management related issue. > >> One example I'm aware the approach as in this RFC wouldn't work is > >> when a device in a SoC belongs to a power domain, which needs to be > >> first switched on before we can start setting up and the clocks' > >> configuration get lost after the power domain switch off. > > > > I like Sylwester's approach of handling this one-time setup in the > > driver core. > > > > Any kind of fine grained power management should not be hidden by DT, > > and by definition that logic belongs in the device driver. It can still > > be nicely abstracted away by runtime pm[1]. > > > > Regards, > > Mike > > > > [1] Message-ID: <20140320114238.GQ7528@xxxxxxxxxxxxxxxxxxxxxx> > How can I access this reference? I was trying to provide a reference to this thread which is tangentially related to this topic: http://www.spinics.net/lists/arm-kernel/msg317016.html But it hadn't hit any of the mail archives at the time of my writing so I just copied Russell's Message-ID from his email. If you have a copy of that email then you can search on Message-ID's for that and you will find it. :-) Regards, Mike > > Thanks, > Maxime > > > > >> > >> OTOH I suspect devices for which one-time clocks setup is sufficient > >> will be quite common. And for these there would need to be a single > >> call to the setup routine in probe() I guess, since it wouldn't be > >> possible to figure out just from the DT data when the actual call > >> should be made. > >> > >> For a global clocks configuration, I thought about specifying that > >> in the clocks controller node, and then to have the setup routine > >> called e.g. from of_clk_init(). I think that could work well enough, > >> together with the patch [1], adding clock dependencies handling. > >> But then the clock frequency set up function would need to be > >> modified to respect the clock parent relationships, similarly as > >> in patch series [2]. A just noticed [2] recently, after posting > >> this RFC (adding Tero at Cc). > >> > >> -- > >> Regards, > >> Sylwester > >> > >> [1] http://www.spinics.net/lists/arm-kernel/msg310507.html > >> [2] http://www.spinics.net/lists/linux-omap/msg103069.html -- 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
