linux-kernel - Re: Re: [PATCH v8 2/3] clock: eswin: Add eic7700 clock driver

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Message-ID: <6077b3be.17c4.19b4564be0d.Coremail.dongxuyang@eswincomputing.com>
Date: Mon, 22 Dec 2025 17:29:48 +0800 (GMT+08:00)
From: "Xuyang Dong" <dongxuyang@...incomputing.com>
To: "Troy Mitchell" <troy.mitchell@...ux.dev>, "Bo Gan" <ganboing@...il.com>,
	mturquette@...libre.com, sboyd@...nel.org, robh@...nel.org,
	krzk+dt@...nel.org, conor+dt@...nel.org, linux-clk@...r.kernel.org,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
	bmasney@...hat.com
Cc: ningyu@...incomputing.com, linmin@...incomputing.com,
	huangyifeng@...incomputing.com, pinkesh.vaghela@...fochips.com
Subject: Re: Re: [PATCH v8 2/3] clock: eswin: Add eic7700 clock driver

> > 
> > ...
> > 
> > > > +static int clk_pll_set_rate(struct clk_hw *hw, unsigned long rate,
> > > > +			    unsigned long parent_rate)
> > > > +{
> > > > +	struct eswin_clk_pll *clk = to_pll_clk(hw);
> > > > +	struct clk *clk_cpu_lp_pll = NULL;
> > > > +	struct clk *clk_cpu_mux = NULL;
> > > > +	struct clk *clk_cpu_pll = NULL;
> > > > +	u32 postdiv1_val = 0, refdiv_val = 1;
> > > > +	u32 frac_val, fbdiv_val, val;
> > > > +	bool lock_flag = false;
> > > > +	int try_count = 0;
> > > > +	int ret;
> > > > +
> > > > +	ret = eswin_calc_pll(&frac_val,  &fbdiv_val, (u64)rate, clk);
> > > > +	if (ret)
> > > > +		return ret;
> > > > +
> > > > +	/* Must switch the CPU to other CLK before we change the CPU PLL. */
> > > > +	if (clk->id == EIC7700_CLK_PLL_CPU) {
> > > > +		clk_cpu_mux = __clk_lookup("mux_cpu_root_3mux1_gfree");
> > > It seems you want to switch to a safe clock source before setting up the
> > > PLL, right?
> > > 
> > > I am not sure whether your approach is correct, but the use of
> > > __clk_lookup() should be avoided whenever possible.
> > > Would it be feasible to obtain a proper clock handle somewhere and
> > > perform the necessary configuration from within a clk_notifier instead?
> > > > +		if (!clk_cpu_mux) {
> > > > +			pr_err("failed to get clk: %s\n",
> > > > +			       "mux_cpu_root_3mux1_gfree");
> > > > +			return -EINVAL;
> > > > +		}
> > 
> > I have a strong feeling that this switch to safe clock and back to PLL
> > can be done with something very similar to this:
> > 
> > "Add notifier for PLL0 clock and set it 1.5GHz on the JH7110 SoC"
> > https://lore.kernel.org/all/20240826080430.179788-1-xingyu.wu@starfivetech.com/
> > 
> YES, That's what I want.
> Thanks for your link!
> 
>                     - Troy
> > Please take a look. Thanks!
> > 
> > Bo

Thanks. The mentioned problems will be corrected in the subsequent patch version.

Regards,
Xuyang Dong