On 1/10/19 18:29, Greg Kroah-Hartman wrote: > 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 Ok, i was expecting that. Thanks for confirming! BR, Georgi
