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Date: Thu, 16 May 2024 18:15:18 +0100
From: Conor Dooley <conor@kernel.org>
To: Frank Li <Frank.li@nxp.com>
Cc: Shengjiu Wang <shengjiu.wang@gmail.com>,
	Stephen Boyd <sboyd@kernel.org>,
	Shengjiu Wang <shengjiu.wang@nxp.com>, abelvesa@kernel.org,
	peng.fan@nxp.com, mturquette@baylibre.com, robh@kernel.org,
	krzk+dt@kernel.org, conor+dt@kernel.org, shawnguo@kernel.org,
	s.hauer@pengutronix.de, kernel@pengutronix.de, festevam@gmail.com,
	marex@denx.de, linux-clk@vger.kernel.org, imx@lists.linux.dev,
	devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org, p.zabel@pengutronix.de
Subject: Re: [PATCH v3 3/6] dt-bindings: clock: imx8mp: Add reset-controller
 sub-node
Message-ID: <20240516-reversing-demeanor-def651bc82ac@spud>
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On Wed, May 15, 2024 at 02:28:51PM -0400, Frank Li wrote:
> On Wed, May 15, 2024 at 05:04:48PM +0100, Conor Dooley wrote:
> > On Wed, May 15, 2024 at 10:47:57AM +0800, Shengjiu Wang wrote:
> > > On Wed, May 15, 2024 at 5:09=E2=80=AFAM Stephen Boyd <sboyd@kernel.or=
g> wrote:
> > > >
> > > > Quoting Conor Dooley (2024-05-14 11:06:14)
> > > > > On Tue, May 14, 2024 at 05:33:27PM +0800, Shengjiu Wang wrote:
> > > > > > diff --git a/Documentation/devicetree/bindings/clock/imx8mp-aud=
iomix.yaml b/Documentation/devicetree/bindings/clock/imx8mp-audiomix.yaml
> > > > > > index 0a6dc1a6e122..a403ace4d11f 100644
> > > > > > --- a/Documentation/devicetree/bindings/clock/imx8mp-audiomix.y=
aml
> > > > > > +++ b/Documentation/devicetree/bindings/clock/imx8mp-audiomix.y=
aml
> > > > > > @@ -15,7 +15,10 @@ description: |
> > > > > >
> > > > > >  properties:
> > > > > >    compatible:
> > > > > > -    const: fsl,imx8mp-audio-blk-ctrl
> > > > > > +    items:
> > > > > > +      - const: fsl,imx8mp-audio-blk-ctrl
> > > > > > +      - const: syscon
> > > > > > +      - const: simple-mfd
> > > > > >
> > > > > >    reg:
> > > > > >      maxItems: 1
> > > > > > @@ -44,6 +47,11 @@ properties:
> > > > > >        ID in its "clocks" phandle cell. See include/dt-bindings=
/clock/imx8mp-clock.h
> > > > > >        for the full list of i.MX8MP IMX8MP_CLK_AUDIOMIX_ clock =
IDs.
> > > > > >
> > > > > > +  reset-controller:
> > > > > > +    type: object
> > > > > > +    $ref: /schemas/reset/fsl,imx8mp-audiomix-reset.yaml#
> > > > > > +    description: The child reset devices of AudioMIX Block Con=
trol.
> > > > >
> > > > > Why not just set #reset-cells =3D <1> in the existing node? IIRC =
it was
> > > > > already suggested to you to do that and use auxdev to set up the =
reset
> > > > > driver.
> > > >
> > > > Yes, do that.
> > >=20
> > > Can I know why sub nodes can't be used? the relationship of parent and
> > > child devices looks better with sub nodes.
> >=20
> > That's pretty subjective. I don't think it looks better to have a clock
> > node that is also a syscon with a reset child node as it is rather
> > inconsistent.
>=20
> I think it is multi function device syscon node. it should be like
>=20
> mfd
> {
> 	clock
> 	{
> 		...
> 	}
>=20
> 	reset
> 	{
> 		...
> 	}
> }
>=20
> clock and reset are difference device node with totally difference's
> compatible string.

Which is I suspect is gonna require a change to your clock driver,
because the range in the existing clock nodes:
	audio_blk_ctrl: clock-controller@30e20000 {
		compatible =3D "fsl,imx8mp-audio-blk-ctrl";
		reg =3D <0x30e20000 0x10000>;
	};
would then have to move to the mfd parent node, and your clock child
would have a reg property that overlaps the reset region. You'd need to
then define a new binding that splits the range in two - obviously
doable, but significantly more work and more disruptive than using an
auxdev.

> > > A further question is can I use the reset-ti-syscon? which is a gener=
ic reset
> > > device for SoCs.  with it I don't even need to write a new reset devi=
ce driver.
> > > it is more simple.
> >=20
> > That is for a TI SoC. You're working on an imx. I don't think that you
> > should be using that...
>=20
> I think this statement violate the linux basic reuse prinicple. If the
> code logic are the same why need duplicate it just because it is differen=
ce
> company. Of coures, if it is generic enough, it'd better to add a more
> generic compatible string.

That's true, but I suspect it only works because only through (ab)use
of the ti,reset-bits property not because you're actually compatible
with TI's reset hardware.

Cheers,
Conor.

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