linux-kernel - Re: [PATCH v2] clk: fixed-factor: add optional dt-binding clock-flags

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Message-ID: <20160702002030.GF27880@codeaurora.org>
Date:	Fri, 1 Jul 2016 17:20:30 -0700
From:	Stephen Boyd <sboyd@...eaurora.org>
To:	Jongsung Kim <neidhard.kim@....com>
Cc:	Michael Turquette <mturquette@...libre.com>,
	Rob Herring <robh@...nel.org>,
	Maxime Ripard <maxime.ripard@...e-electrons.com>,
	linux-clk@...r.kernel.org, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org, Chanho Min <chanho.min@....com>
Subject: Re: [PATCH v2] clk: fixed-factor: add optional dt-binding clock-flags

On 06/29, Jongsung Kim wrote:
> On 2016년 06월 29일 06:18, Michael Turquette wrote:
> > Quoting Rob Herring (2016-06-28 13:55:18)
> >> On Fri, Jun 24, 2016 at 01:12:52PM +0900, Jongsung Kim wrote:
> >>> There is no way to set additional flags for a DT-initialized fixed-
> >>> factor-clock, and it can be problematic i.e., when the clock rate
> >>> needs to be changed. [1][2]
> >>>
> >>> This patch introduces an optional dt-binding named "clock-flags" to
> >>> be used for passing any needed flags from dts.
> >> I don't think we want this in DT. If we did, the flags would need some 
> >> documentation about what the flags mean.
> > Flags are specific to Linux implementation, so I agree with Rob. Better
> > to create a compatible string for your hardware that bakes in the flags.
> 
> Thank you for your comment, Mike. This conversation starts from lacking method to set CLK_SET_RATE_PARENT from DT. I understand compatible string can be a solution. But.. if someone starts talking about lacking method to set another flag, i.e., CLK_SET_PARENT_GATE, then we'll need another compatible string list.
> How do you think about defining possible required subset of the flags and using some more neutral flag-names acceptable in DT?

Do you actually have an IC on the board that is doing some fixed
factor calculation? Or is this a clk driver design where we are
listing out each piece of an SoC's clk controller in DT?

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