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

From: Daniel Baluta <daniel.baluta@gmail.com>
To: Ulf Hansson <ulf.hansson@linaro.org>
Cc: Daniel Baluta <daniel.baluta@oss.nxp.com>,
	Aisheng Dong <aisheng.dong@nxp.com>,
	Len Brown <len.brown@intel.com>,
	Linux-ALSA <alsa-devel@alsa-project.org>,
	Linux PM <linux-pm@vger.kernel.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Sascha Hauer <s.hauer@pengutronix.de>,
	Kevin Hilman <khilman@kernel.org>,
	"Rafael J. Wysocki" <rjw@rjwysocki.net>,
	Ranjani Sridharan <ranjani.sridharan@linux.intel.com>,
	Daniel Baluta <daniel.baluta@nxp.com>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Paul Olaru <paul.olaru@nxp.com>, dl-linux-imx <linux-imx@nxp.com>,
	Sascha Hauer <kernel@pengutronix.de>,
	Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>,
	Shawn Guo <shawnguo@kernel.org>,
	Fabio Estevam <festevam@gmail.com>,
	"S.j. Wang" <shengjiu.wang@nxp.com>,
	Linux ARM <linux-arm-kernel@lists.infradead.org>,
	Anson Huang <anson.huang@nxp.com>
Subject: Re: [RFC PATCH v2 1/2] PM / domains: Introduce multi PM domains helpers
Date: Tue, 21 Apr 2020 17:18:45 +0300	[thread overview]
Message-ID: <CAEnQRZDX8PZ7V+c8zfoxK-+oGp2pt8N3oTAC6=Ps1W33LGY7WA@mail.gmail.com> (raw)
In-Reply-To: <CAPDyKFp6KLuuuVFcEWGxn5NkuDSkhM-MjRiiYj_zC4mFxhOBag@mail.gmail.com>

On Tue, Apr 21, 2020 at 5:01 PM Ulf Hansson <ulf.hansson@linaro.org> wrote:
>
> On Wed, 4 Mar 2020 at 13:20, Daniel Baluta <daniel.baluta@oss.nxp.com> wrote:
> >
> > From: Daniel Baluta <daniel.baluta@nxp.com>
> >
> > 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@nxp.com>
>
> 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.