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

Troy Mitchell
2025-12-20T03:26:00Z

On Fri, Dec 19, 2025 at 02:39:41PM -0800, Bo Gan wrote:
> Hi ESWIN folks,
>
> Please refer to my comments below
>
> On 12/18/25 18:50, Troy Mitchell wrote:
> > Hi Xuyang,
> > This is a quick review.
> >
> > On Thu, Nov 13, 2025 at 09:38:46AM +0800, dongxuyang@eswincomputing.com wrote:
> > > From: Xuyang Dong <dongxuyang@eswincomputing.com>
> > >
>
> ...
>
> > > +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