Hi Greg, On 12/17/18 13:17, Georgi Djakov wrote: > Hi Greg, > > On 12/11/18 08:58, Greg Kroah-Hartman wrote: >> On Mon, Dec 10, 2018 at 04:50:00PM +0200, Georgi Djakov wrote: >>> On 12/10/18 13:00, Rafael J. Wysocki wrote: >>>> On Mon, Dec 10, 2018 at 11:18 AM Georgi Djakov <georgi.djakov@xxxxxxxxxx> wrote: >>>>> >>>>> Hi Rafael, >>>>> >>>>> On 12/10/18 11:04, Rafael J. Wysocki wrote: >>>>>> On Thu, Dec 6, 2018 at 3:55 PM Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> wrote: >>>>>>> >>>>>>> On Wed, Dec 05, 2018 at 12:41:35PM -0800, Evan Green wrote: >>>>>>>> On Tue, Nov 27, 2018 at 10:03 AM Georgi Djakov <georgi.djakov@xxxxxxxxxx> wrote: >>>>>>>>> >>>>>>>>> Modern SoCs have multiple processors and various dedicated cores (video, gpu, >>>>>>>>> graphics, modem). These cores are talking to each other and can generate a >>>>>>>>> lot of data flowing through the on-chip interconnects. These interconnect >>>>>>>>> buses could form different topologies such as crossbar, point to point buses, >>>>>>>>> hierarchical buses or use the network-on-chip concept. >>>>>>>>> >>>>>>>>> These buses have been sized usually to handle use cases with high data >>>>>>>>> throughput but it is not necessary all the time and consume a lot of power. >>>>>>>>> Furthermore, the priority between masters can vary depending on the running >>>>>>>>> use case like video playback or CPU intensive tasks. >>>>>>>>> >>>>>>>>> Having an API to control the requirement of the system in terms of bandwidth >>>>>>>>> and QoS, so we can adapt the interconnect configuration to match those by >>>>>>>>> scaling the frequencies, setting link priority and tuning QoS parameters. >>>>>>>>> This configuration can be a static, one-time operation done at boot for some >>>>>>>>> platforms or a dynamic set of operations that happen at run-time. >>>>>>>>> >>>>>>>>> This patchset introduce a new API to get the requirement and configure the >>>>>>>>> interconnect buses across the entire chipset to fit with the current demand. >>>>>>>>> The API is NOT for changing the performance of the endpoint devices, but only >>>>>>>>> the interconnect path in between them. >>>>>>>> >>>>>>>> For what it's worth, we are ready to land this in Chrome OS. I think >>>>>>>> this series has been very well discussed and reviewed, hasn't changed >>>>>>>> much in the last few spins, and is in good enough shape to use as a >>>>>>>> base for future patches. Georgi's also done a great job reaching out >>>>>>>> to other SoC vendors, and there appears to be enough consensus that >>>>>>>> this framework will be usable by more than just Qualcomm. There are >>>>>>>> also several drivers out on the list trying to add patches to use this >>>>>>>> framework, with more to come, so it made sense (to us) to get this >>>>>>>> base framework nailed down. In my experiments this is an important >>>>>>>> piece of the overall power management story, especially on systems >>>>>>>> that are mostly idle. >>>>>>>> >>>>>>>> I'll continue to track changes to this series and we will ultimately >>>>>>>> reconcile with whatever happens upstream, but I thought it was worth >>>>>>>> sending this note to express our "thumbs up" towards this framework. >>>>>>> >>>>>>> Looks like a v11 will be forthcoming, so I'll wait for that one to apply >>>>>>> it to the tree if all looks good. >>>>>> >>>>>> I'm honestly not sure if it is ready yet. >>>>>> >>>>>> New versions are coming on and on, which may make such an impression, >>>>>> but we had some discussion on it at the LPC and some serious questions >>>>>> were asked during it, for instance regarding the DT binding introduced >>>>>> here. I'm not sure how this particular issue has been addressed here, >>>>>> for example. >>>>> >>>>> There have been no changes in bindings since v4 (other than squashing >>>>> consumer and provider bindings into a single patch and fixing typos). >>>>> >>>>> The last DT comment was on v9 [1] where Rob wanted confirmation from >>>>> other SoC vendors that this works for them too. And now we have that >>>>> confirmation and there are patches posted on the list [2]. >>>> >>>> OK >>>> >>>>> The second thing (also discussed at LPC) was about possible cases where >>>>> some consumer drivers can't calculate how much bandwidth they actually >>>>> need and how to address that. The proposal was to extend the OPP >>>>> bindings with one more property, but this is not part of this patchset. >>>>> It is a future step that needs more discussion on the mailing list. If a >>>>> driver really needs some bandwidth data now, it should be put into the >>>>> driver and not in DT. After we have enough consumers, we can discuss >>>>> again if it makes sense to extract something into DT or not. >>>> >>>> That's fine by me. >>>> >>>> Admittedly, I have some reservations regarding the extent to which >>>> this approach will turn out to be useful in practice, but I guess as >>>> long as there is enough traction, the best way to find out it to try >>>> and see. :-) >>>> >>>> From now on I will assume that this series is going to be applied by Greg. >>> >>> That was the initial idea, but the problem is that there is a recent >>> change in the cmd_db API (needed by the sdm845 provider driver), which >>> is going through arm-soc/qcom/drivers. So either Greg pulls also the >>> qcom-drivers-for-4.21 tag from Andy or the whole series goes via Olof >>> and Arnd. Maybe there are other options. I don't have any preference and >>> don't want to put extra burden on any maintainers, so i am ok with what >>> they prefer. >> >> Let me take the time later this week to review the code, which I haven't >> done in a while... >> > > When you get a chance to review, please keep in mind that the latest > version is v12 (from 08.Dec). The same is also available in linux-next > with no reported issues. The dependencies for this patchset have been already merged in v5.0-rc1, so i was wondering if this can still go into -rc2? Various patches that use this API are already posted and having it sooner will make dealing with dependencies and merge paths a bit easier during the next merge window. Or i can just rebase and resend everything targeting v5.1. Thanks, Georgi
