On 1/10/19 18:29, Greg Kroah-Hartman wrote:

On Thu, Jan 10, 2019 at 04:19:14PM +0200, Georgi Djakov wrote:

quoted

Hi Greg,

On 12/17/18 13:17, Georgi Djakov wrote:

quoted

Hi Greg,

On 12/11/18 08:58, Greg Kroah-Hartman wrote:

quoted

On Mon, Dec 10, 2018 at 04:50:00PM +0200, Georgi Djakov wrote:

quoted

On 12/10/18 13:00, Rafael J. Wysocki wrote:

quoted

On Mon, Dec 10, 2018 at 11:18 AM Georgi Djakov [off-list ref] wrote:

quoted

Hi Rafael,

On 12/10/18 11:04, Rafael J. Wysocki wrote:

quoted

On Thu, Dec 6, 2018 at 3:55 PM Greg KH [off-list ref] wrote:

quoted

On Wed, Dec 05, 2018 at 12:41:35PM -0800, Evan Green wrote:

quoted

On Tue, Nov 27, 2018 at 10:03 AM Georgi Djakov [off-list ref] wrote:

quoted

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

quoted

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

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel