Re: [RFC PATCH v2 1/2] PM / domains: Introduce multi PM domains helpers

[Daniel Baluta]

On Tue, Apr 21, 2020 at 5:01 PM Ulf Hansson <ulf.hansson@xxxxxxxxxx> wrote:
>
> On Wed, 4 Mar 2020 at 13:20, Daniel Baluta <daniel.baluta@xxxxxxxxxxx> wrote:
> >
> > From: Daniel Baluta <daniel.baluta@xxxxxxx>
> >
> > This patch introduces helpers support for multi PM domains.
> >
> > API consists of:
> >
> > 1) dev_multi_pm_attach - powers up all PM domains associated with a given
> > device. Because we can attach one PM domain per device, we create
> > virtual devices (children of initial device) and associate PM domains
> > one per virtual device.
> >
> > 2) dev_multi_pm_detach - detaches all virtual devices from PM domains
> > attached with.
> >
> > Signed-off-by: Daniel Baluta <daniel.baluta@xxxxxxx>
>
> First, apologize for the delay.
>
> In general I don't mind adding helpers that can be used to decrease
> open coding. However, in this case, I wonder how useful the helpers
> would really be.
>
> More precisely, according to the information I have, a device may not
> always need all of its PM domains to be turned on together, but
> perhaps only a subset of them. Depending on the current use case that
> is running.
>
> Of course, some cases follow your expectations, but as stated, some
> others do not.
>
> Do you have an idea how many users that would be able to switch to
> these new APIs as of today?

IMX Sound Open Firmware driver will immediately be available
to use this new API.

https://elixir.bootlin.com/linux/latest/source/sound/soc/sof/imx/imx8.c#L221

Aside, from that there are the ACM clock modules for i.MX8QXP / i.MX8QM. Also,
looking at our internal tree there are XUVI, VPU, DPU drivers that need multi
power domain support.

Anson, Aisheng do you have a number of users on your side for
multi power domain?

thanks,
daniel.