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

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Message-ID:
 <PAXPR04MB8459C5A372FADDD970BCA33088B42@PAXPR04MB8459.eurprd04.prod.outlook.com>
Date: Fri, 26 Jul 2024 09:28:52 +0000
From: Peng Fan <peng.fan@....com>
To: Dhruva Gole <d-gole@...com>, "Peng Fan (OSS)" <peng.fan@....nxp.com>
CC: "sudeep.holla@....com" <sudeep.holla@....com>, "cristian.marussi@....com"
	<cristian.marussi@....com>, "mturquette@...libre.com"
	<mturquette@...libre.com>, "sboyd@...nel.org" <sboyd@...nel.org>,
	"linux-clk@...r.kernel.org" <linux-clk@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org"
	<linux-arm-kernel@...ts.infradead.org>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, "arm-scmi@...r.kernel.org"
	<arm-scmi@...r.kernel.org>, "vigneshr@...com" <vigneshr@...com>,
	"kamlesh@...com" <kamlesh@...com>
Subject: RE: [PATCH] clk: scmi: add is_prepared hook

> 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?

This patch is for non-atomic clk ops. The is_enabled hook is
In atomic clk ops.

> 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

SCMI firmware has no knowledge of prepare/unprepared.

As wrote in the beginning, this patch is for non atomic clk ops.

Regards,
Peng.

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