linux-kernel - Re: [PATCH v2 1/6] dt-bindings: clock: imx8m: document nominal/overdrive properties

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Message-ID: <ismbe2ne65ew2jkcoa2tmbjz2eajvuz5bxuwef3wptj7tkvqhn@norm5p52aygr>
Date: Tue, 7 Jan 2025 07:52:38 +0100
From: Krzysztof Kozlowski <krzk@...nel.org>
To: Ahmad Fatoum <a.fatoum@...gutronix.de>
Cc: Frank Li <Frank.li@....com>, Conor Dooley <conor+dt@...nel.org>, 
	Abel Vesa <abelvesa@...nel.org>, Peng Fan <peng.fan@....com>, 
	Michael Turquette <mturquette@...libre.com>, Stephen Boyd <sboyd@...nel.org>, Rob Herring <robh@...nel.org>, 
	Krzysztof Kozlowski <krzk+dt@...nel.org>, Shawn Guo <shawnguo@...nel.org>, 
	Sascha Hauer <s.hauer@...gutronix.de>, Pengutronix Kernel Team <kernel@...gutronix.de>, 
	Fabio Estevam <festevam@...il.com>, Abel Vesa <abel.vesa@...aro.org>, Marek Vasut <marex@...x.de>, 
	linux-clk@...r.kernel.org, imx@...ts.linux.dev, devicetree@...r.kernel.org, 
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org, 
	Conor Dooley <conor.dooley@...rochip.com>
Subject: Re: [PATCH v2 1/6] dt-bindings: clock: imx8m: document
 nominal/overdrive properties

On Mon, Jan 06, 2025 at 08:55:08PM +0100, Ahmad Fatoum wrote:
> >>> why need two flags? suppose "not set fsl,overdrive-mode" is equal to
> >>> fsl,nominal-mode
> >>
> >> Conor had the same question on v1[1] and I have addressed this in the commit
> >> message of v2, see above.
> >>
> >> In short, there is unfortunately no universally applicable default.
> >>
> >> [1]: https://lore.kernel.org/all/4e2250b3-5170-4e88-aa0a-dd796b81e78b@pengutronix.de/
> >>
> > 
> > But there are problem if use dts overlay because dts overlay can't support
> > delete property.
> > 
> > If one dts file use "fsl,overdrive-mode", dts overlay file can't delete
> > this property. "mutually exclusive optional properties" was not preferred.
> > 
> > mode = ["normal" | "overdrive"]
> 
> I don't see myself setting this via overlay, but if you say it's useful, we can
> adjust the binding.
> 
> I am not sure what's the preference is though, should we have
> 
>   fsl,operating-mode = "normal" / "overdrive"
> 
> or 
> 
>   fsl,operating-mode = <IMX_OPMODE_NORMAL> / <IMX_OPMODE_OVERDRIVE>
> 
> 
> Any idea? Conor?

If these are two exclusive modes (plus default), then as Frank
suggested: use enum of strings. Imagine encoding enum of 10 values with
bools as you did: that would be enourmous oneOf condition or if:then:.

Preferred is strings, but numerical values are also accepted.

Best regards,
Krzysztof