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

Bo Gan
2025-12-19T22:41:34Z

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/

Please take a look. Thanks!

Bo