linux-kernel - Re: [PATCH V2 2/2] clk: scmi: support state_ctrl

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Date: Wed, 10 Jan 2024 15:40:25 +0000
From: Cristian Marussi <cristian.marussi@....com>
To: "Peng Fan (OSS)" <peng.fan@....nxp.com>
Cc: sudeep.holla@....com, mturquette@...libre.com, sboyd@...nel.org,
	linux-arm-kernel@...ts.infradead.org, linux-clk@...r.kernel.org,
	linux-kernel@...r.kernel.org, ranjani.vaidyanathan@....com,
	glen.wienecke@....com, nitin.garg_3@....com, chuck.cannon@....com,
	Peng Fan <peng.fan@....com>
Subject: Re: [PATCH V2 2/2] clk: scmi: support state_ctrl_forbidden

On Thu, Dec 07, 2023 at 05:33:45PM +0800, Peng Fan (OSS) wrote:
> From: Peng Fan <peng.fan@....com>
> 
> Some clocks may exported to linux, while those clocks are not allowed
> to configure by Linux. For example:
> 

Hi,

> SYS_CLK1-----
>              \
> 	     --MUX--->MMC1_CLK
>              /
> SYS_CLK2-----
> 
> MMC1 needs set parent, so SYS_CLK1 and SYS_CLK2 are exported to Linux,
> then the clk propagation will touch SYS_CLK1 or SYS_CLK2.
> So we need bypass the failure for SYS_CLK1 or SYS_CLK2 when enable
> the clock of MMC1.
> 


So I was puzzled a bit at first (as said) by the fact that here we
silently swallow the failure if the SCMI Clock cannot be disabled, BUT
then I spotted in include/linux/clk.h

	/**
	 * clk_enable - inform the system when the clock source should be running.
	 * @clk: clock source
	 *
	 * If the clock can not be enabled/disabled, this should return success.

..so I suppose it is fine for the CLK framework at the end.

My next remaining question is why are you not doing the same when
(ret == -EACCES && clk->info->state_ctrl_forbidden) for atomic_ops ?

I.e. in:

	clk-scmi.c::static int scmi_clk_atomic_enable(struct clk_hw *hw)

Any particular reason (beside not needing it in your particular case...)

Thanks,
Cristian