Re: [PATCH v7 6/9] interconnect: qcom: rpm: Handle interface clocks

[Georgi Djakov]

On 21.03.23 16:11, Konrad Dybcio wrote:
> On 21.03.2023 14:58, Georgi Djakov wrote:
> > Hi,
> >
> > On 11.03.23 17:26, Dmitry Baryshkov wrote:
> > > On 11/03/2023 16:38, Bryan O'Donoghue wrote:
> > > > On 11/03/2023 14:35, Dmitry Baryshkov wrote:
> > > > > > Its probably worthwhile experimenting to see if the*ufs*_clk can/should
> > > > > > be added to the UFS device list of clocks.
> > > > > While we were doing this for some of the clocks (PCIe and USB, if I'm
> > > > > not mistaken), I think that generally this is not fully correct. In my
> > > > > opinion it should be in the interconnect driver, who turns
> > > > > corresponding clocks on and off. These clocks correspond to the SoC
> > > > > topology, rather than the end-device.
> > > >
> > > > True enough, they are interconnect clocks.
> > > >
> > > > The question is how to only turn them on when the device that depends on them wants them.
> > >
> > > I think we can turn them on an off from qcom_icc_set(). Each node can list required clocks.
> >
> > Yes, this is a bit weird, but looks like these are the interface clocks
> > required for programming the qos box of the respective peripheral and
> > nothing else. Maybe we can even configure QoS just once (eg. on the first
> > bandwidth request) and not every time we call qcom_icc_set().
> Would that persist a full bus reset - if we e.g. shut down MMNoC
> after the display stack is turned off in preparation for a power
> collapse, would we have to reprogram it?
>
> Another thing is, do we know "how persistent" the QoS settings are?
> What could reset them? Would a bandwidth request for a node that
> belongs to the same path do so?

That's a good question. From what i recall, i expect them to persist until
you reset the board. Probably we can verify it with an experiment by reading
them back, but let me check if i can find some info.

Thanks,
Georgi