On Mon, Jun 25, 2018 at 2:03 PM Matthias Kaehlcke <mka@xxxxxxxxxxxx> wrote: > > On Mon, Jun 25, 2018 at 11:50:37AM -0700, Matthias Kaehlcke wrote: > > Hi Rob, > > > > On Mon, Jun 25, 2018 at 09:33:41AM -0600, Rob Herring wrote: > > > On Wed, Jun 20, 2018 at 06:52:34PM -0700, Matthias Kaehlcke wrote: > > > > The optional opp-throttlers property is used to configure the throttlers > > > > (see drivers/misc/throttler/*) that use a given OPP to throttle the > > > > corresponding device(s). > > > > > > > > Signed-off-by: Matthias Kaehlcke <mka@xxxxxxxxxxxx> > > > > Reviewed-by: Brian Norris <briannorris@xxxxxxxxxxxx> > > > > --- > > > > Changes in v4: > > > > - added 'Reviewed-by: Brian Norris <briannorris@xxxxxxxxxxxx>' tag > > > > > > > > Changes in v3: > > > > - none > > > > > > > > Changes in v2: > > > > - patch added to series > > > > --- > > > > Documentation/devicetree/bindings/opp/opp.txt | 3 +++ > > > > 1 file changed, 3 insertions(+) > > > > > > > > diff --git a/Documentation/devicetree/bindings/opp/opp.txt b/Documentation/devicetree/bindings/opp/opp.txt > > > > index c396c4c0af92..747e79740c75 100644 > > > > --- a/Documentation/devicetree/bindings/opp/opp.txt > > > > +++ b/Documentation/devicetree/bindings/opp/opp.txt > > > > @@ -170,6 +170,9 @@ Optional properties: > > > > functioning of the current device at the current OPP (where this property is > > > > present). > > > > > > > > +- opp-throttlers: Array with phandles of throttlers that use this OPP to > > > > + throttle the corresponding device(s). > > > > + > > > > > > I think it would be better to make this a boolean for each OPP entry and > > > then add "operating-points-v2" property to the EC node to point to the > > > OPP table. > > > > Thanks for your suggestion. "operating-points-v2" would have to be an > > array of phandles, a single thottler can have multiple throttling > > devices. I don't see any issue with allowing that. > > > Unless there is some need for a different throttler for each OPP entry? > > > > Having the option to use different OPPs per throttler would be my > > preference. E.g. there could be configurations where one throttler > > only interacts with certain throttling devices and another one > > with others. Your terminology is confusing. By "throttling device", you mean an OPP table (or OPP entry) which is not a device. OPPs are just a table of state information. > > I see another option to achieve this, if you don't like the reference > > to the throttlers in the OPPs. The throttler could have a list of OPPs > > (as phandles, not frequencies as in v1). The main inconvenient I see > > here is that the used OPPs would need a label, which they usually > > don't have. Maybe this is no soooo bad, since the label could be added > > at device level, only on devices that use a throttler, so it wouldn't > > clutter the platform .dts files. > > > > This could be a single array with all OPPs from different devices, > > or multiple arrays, one for each throttling device: > > > > throttler-opps-0 = <&cpu0_opp_03 &cpu0_opp_05>; > > throttler-opps-1 = <&gpu_opp_02 &gpu_opp_04>; > > > > My preference would be multiple arrays, because it's easier to read. > > I take the preference back. The OPPs for each device (group) can be > clustered within the single array and if needed clarifying comments > can be added: > > throttler-opps = <&cpu0_opp_03 &cpu0_opp_05 /* CPU0 */ > &gpu_opp_02 &gpu_opp_04>; /* GPU */ > > This is simpler algorithmically and there is no need for an additional > property indicating the number of OPP groups or probing. I'm still trying to understand why you would have say throttler-A wanting to set cpu freq to X and throttler-B wanting to set cpu freq to Y. There's both the question of why/when would you have 2 or more throttlers (in DT) and how would you resolve multiple requests. The whole design of a throttler directly dealing with OPPs especially for non-cpu devices seems like it is missing some level of abstraction. What if you want to throttle by some means other than frequency such as idling cores? I guess abstraction would make it hard to make things optimal for every platform when in the end you just want to set specific frequencies on a number of devices. It seems like a similar situation as early big.LITTLE designs vs. EAS. Rob -- 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
