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From:   Stephen Boyd <sboyd@kernel.org>
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Subject: RE: [PATCH 2/2] clk: imx: imx7d: remove clks_init_on array
Date:   Tue, 16 Oct 2018 15:24:35 -0700
Sender: linux-kernel-owner@vger.kernel.org
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Quoting Anson Huang (2018-10-15 21:37:31)
> Hi, Stephen
> =

> Anson Huang
> Best Regards!
> =

> =

> > -----Original Message-----
> > From: Stephen Boyd <sboyd@kernel.org>
> > Sent: Tuesday, October 16, 2018 12:46 AM
> > To: kernel@pengutronix.de; linux-arm-kernel@lists.infradead.org;
> > linux-clk@vger.kernel.org; linux-kernel@vger.kernel.org;
> > mturquette@baylibre.com; s.hauer@pengutronix.de; shawnguo@kernel.org;
> > Anson Huang <anson.huang@nxp.com>; Fabio Estevam
> > <fabio.estevam@nxp.com>; Jerome Forissier <jerome.forissier@linaro.org>;
> > Peng Fan <peng.fan@nxp.com>; Rob Herring <robh@kernel.org>
> > Cc: dl-linux-imx <linux-imx@nxp.com>
> > Subject: RE: [PATCH 2/2] clk: imx: imx7d: remove clks_init_on array
> > =

> > Quoting Anson Huang (2018-10-15 02:33:35)
> > > > > > >
> > > > > >
> > > > > > Why can't we add clks to the op-tee node in DT's /firmware cont=
ainer?
> > > > > > Then any clks in there can be turned on forever and left enabled
> > > > > > by the linux driver?
> > > > >
> > > > > I did NOT run op-tee with Linux-next kernel before, can you advis=
e more?
> > > >
> > > > Neither have I, so I can't advise more.
> > > >
> > > > > And I think if op-tee has such requirement, can we have another
> > > > > patch to cover it?
> > > >
> > > > Yes.
> > > >
> > > >
> > > > > I believe all other i.MX platforms also have same requirements if
> > > > > considering op-tee support, so I think it should be another topic,
> > > > > what do you
> > > > think?
> > > > >
> > > >
> > > > I'm going to drop these patches from my review queue. Please resend
> > > > them and please include the op-tee patches too.
> > >
> > >
> > > I do NOT know how to include the op-tee patch to meet special
> > > requirement, should the op-tee related patch be added later when some=
one
> > actually add the op-tee support for i.MX7?
> > > It should NOT block this patch set, do you think we can add this patc=
h set
> > first?
> > >
> > =

> > Please resend the two patches. In the commit text for the second patch,
> > describe the plan to remove CLK_IS_CRITICAL from these clks by adding an
> > OP-TEE device/driver to the kernel to keep these clks enabled. My
> > understanding is that there isn't an OP-TEE driver right now, but these=
 clks are
> > used by the firmware and can't be turned off in Linux. If in the future=
 we want
> > to be able to turn them on and off, we'll need to add them to an OP-TEE=
 device
> > node and have that driver manage the clks.
> > =

> > How that will work when a system doesn't enable the OP-TEE driver I'm n=
ot
> > sure. We may need to develop some system whereby clks like this are han=
ded
> > from the clk controller to the consumer driver when it's enabled for fu=
rther
> > power managment, but if they're never handed off, they're kept on forev=
er like
> > is done here. Anyway, please resend with a note about why these are mar=
ked
> > CLK_IS_CRITICAL.
>  =

> I think there is some misunderstanding here, this patch sets those critic=
al clocks
> with CLK_IS_CRITICAL flag to let clock driver keep them always ON, as the=
y are
> critical clocks and system (Linux kernel, NOT include op-tee) can NOT run=
 normally
> if anyone of them is OFF.

Ok it sounds like OP-TEE usage completely orthogonal here? I'll go apply
these refactorings then.