On Thu, Jan 10, 2019 at 04:19:14PM +0200, Georgi Djakov wrote: > 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. We can't add new features after -rc1, sorry. Please rebase and resend to target 5.1 thanks, greg k-h
