linux-kernel - Re: [PATCH v3] clk: set initial best mux parent to current parent with CLK_MUX_ROUND

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Date: Thu, 7 Mar 2024 09:48:09 +0100
From: Maxime Ripard <mripard@...nel.org>
To: forbidden405@...look.com
Cc: Michael Turquette <mturquette@...libre.com>, 
	Stephen Boyd <sboyd@...nel.org>, linux-clk@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] clk: set initial best mux parent to current parent
 with CLK_MUX_ROUND_CLOSEST

Hi,

On Thu, Mar 07, 2024 at 10:03:50AM +0800, Yang Xiwen via B4 Relay wrote:
> From: Yang Xiwen <forbidden405@...look.com>
> 
> Originally, the initial clock rate is hardcoded to 0, this can lead to
> some problem when setting a very small rate with CLK_MUX_ROUND_CLOSEST.
> 
> For example, if the lowest possible rate provided by the mux is 1000Hz,
> setting a rate below 500Hz will fail, because no clock can provide a
> better rate than the non-existant 0Hz. But it should succeed with 1000Hz
> being set.
> 
> Setting the initial best parent to current parent could solve this bug.
> 
> Signed-off-by: Yang Xiwen <forbidden405@...look.com>

I don't think it would be the way to go. The biggest issue to me is that
it's inconsistent, and only changing the behaviour for a given flag
doesn't solve that.

And again, either way, we should document it. And run it through kernelci.

Maxime

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