On 06/17/2015 06:47 AM, Rob Herring wrote: > On Wed, Jun 17, 2015 at 8:33 AM, Viresh Kumar <viresh.kumar@xxxxxxxxxx> wrote: >> On 17-06-15, 08:23, Rob Herring wrote: >>>> + operating-points-v2 = <&cpu0_opp_table_slow>, <&cpu0_opp_table_fast>; >>> You've made a fundamental change here in that this can now be a list >>> of phandles. There should be some description on what a list means >>> (merge the tables?, select one?). >> Did you miss the description I wrote few lines earlier or are you >> asking for something else? This is what I wrote earlier: >> >>>> +Devices may want to choose OPP tables at runtime and so can provide a list of >>>> +phandles here. But only *one* of them should be chosen at runtime. >> So, clearly only ONE of the tables should be used. > Yes, never mind. > >>> I think this needs to have a defined order and the platform should >>> know what that is. For example, if you read the efuses and decide you >>> need the "slow" table, you know to pick the first entry. Then you >>> don't need opp-name. Does that work for QCom? >> Why forcing on the order here? For example, consider a case where the >> platform can have four tables, A B C D. Now DT is free to pass all >> four or just a subset of those. Like, for some boards table B doesn't >> stand valid. And so it may wanna pass just A C D. And so keeping these >> tables in order is going to break for sure. Flexibility is probably >> better in this case. > Defined order is a key part of DT bindings. We solve the variable > length problem with name lists associated with variable length > property like: > > operating-point-names = "slow", "fast"; > > I'm not a fan of doing this if we can avoid it, but we should at least > follow the same pattern. Don't send me a patch with that yet, I want > to hear from Stephen. > > You can also use "status" to disable specific tables rather than > removing from the list. > An operating-point(s?)-names property seems ok... but doesn't that mean that every CPU that uses the OPP has to have the same list of operating-point-names? It would make sense to me if the operating points were called something different depending on *which* CPU is using them, but in this case the only name for the operating point is "slow" or "fast", etc. In reality we've assigned them names like speedX-binY-vZ so that we know which speed bin, voltage bin, and version they're part of. Maybe OPP node properties like qcom,speed-bin = <u32>, qcom,pvs-bin = <u32>, etc. would be better? It would make the parsing code slightly more complicated because it needs to look for 2 or 3 properties instead of a name property though. Or would having different node names be acceptable? That would avoid this list of strings. At the least, operating-points-names will be required on qcom platforms. A fixed ordering known to the platform would mean that we know exactly how many voltage bins and speed bins and how many voltage bins per speed bin are used for a particular SoC, which we've avoided knowing so far. -- Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project -- 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
