Re: [PATCH v10 0/8] Introduce on-chip interconnect API

[Georgi Djakov]

Hi Greg and Evan,

On 12/6/18 16:55, Greg KH 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.
> 

Yes, it's coming. I will also include an additional fixup patch, as the
sdm845 provider driver will fail to build in linux-next, due to a recent
change in the cmd_db API.

Thanks,
Georgi