linux-kernel - Re: [PATCH] clk: scmi: add is

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Message-ID: <20240726085305.sb57f3i2ezvtwrwz@dhruva>
Date: Fri, 26 Jul 2024 14:23:05 +0530
From: Dhruva Gole <d-gole@...com>
To: "Peng Fan (OSS)" <peng.fan@....nxp.com>
CC: <sudeep.holla@....com>, <cristian.marussi@....com>,
        <mturquette@...libre.com>, <sboyd@...nel.org>,
        <linux-clk@...r.kernel.org>, <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <arm-scmi@...r.kernel.org>,
        Peng Fan <peng.fan@....com>, <vigneshr@...com>, <kamlesh@...com>
Subject: Re: [PATCH] clk: scmi: add is_prepared hook

On Jul 25, 2024 at 17:07:41 +0800, Peng Fan (OSS) wrote:
> From: Peng Fan <peng.fan@....com>
> 
> Some clks maybe default enabled by hardware, so add is_prepared hook

Why is_prepared when there is an is_enabled hook?
See in the atomic case we already have something similar:

ops->is_enabled = scmi_clk_atomic_is_enabled;

> to get the status of the clk. Then when disabling unused clks, those
> unused clks but default hardware on clks could be in off state to save
> power.
> 
> Signed-off-by: Peng Fan <peng.fan@....com>
> ---
>  drivers/clk/clk-scmi.c | 15 +++++++++++++++
>  1 file changed, 15 insertions(+)
> 
> diff --git a/drivers/clk/clk-scmi.c b/drivers/clk/clk-scmi.c
> index d86a02563f6c..d2d370337ba5 100644
> --- a/drivers/clk/clk-scmi.c
> +++ b/drivers/clk/clk-scmi.c
> @@ -142,6 +142,20 @@ static void scmi_clk_disable(struct clk_hw *hw)
>  	scmi_proto_clk_ops->disable(clk->ph, clk->id, NOT_ATOMIC);
>  }
>  
> +static int scmi_clk_is_enabled(struct clk_hw *hw)
> +{
> +	int ret;
> +	bool enabled = false;
> +	struct scmi_clk *clk = to_scmi_clk(hw);
> +
> +	ret = scmi_proto_clk_ops->state_get(clk->ph, clk->id, &enabled, NOT_ATOMIC);
> +	if (ret)
> +		dev_warn(clk->dev,
> +			 "Failed to get state for clock ID %d\n", clk->id);
> +
> +	return !!enabled;
> +}
> +
>  static int scmi_clk_atomic_enable(struct clk_hw *hw)
>  {
>  	struct scmi_clk *clk = to_scmi_clk(hw);
> @@ -280,6 +294,7 @@ scmi_clk_ops_alloc(struct device *dev, unsigned long feats_key)
>  		} else {
>  			ops->prepare = scmi_clk_enable;
>  			ops->unprepare = scmi_clk_disable;
> +			ops->is_prepared = scmi_clk_is_enabled;

IMO from the decription and what the function is doing is_enabled makes
more sense here to me, unless there's a better explanation.

Ref: linux/clk-provider.h
is_prepared: Queries the hardware to determine if the clock is prepared
vs
is_enabled: Queries the hardware to determine if the clock is enabled

-- 
Best regards,
Dhruva Gole <d-gole@...com>