Re: [PATCH V3 3/6] clk: meson: S4: add support for Amlogic S4 SoC PLL clock driver

Yu Tu
2022-08-30T07:37:36Z

On 2022/8/30 14:44, Jerome Brunet wrote:
> [ EXTERNAL EMAIL ]
>
>
> On Tue 30 Aug 2022 at 14:13, Yu Tu <yu.tu@amlogic.com> wrote:
>
>> On 2022/8/29 17:48, Jerome Brunet wrote:
>>> [ EXTERNAL EMAIL ]
>>> On Mon 15 Aug 2022 at 21:20, Yu Tu <yu.tu@amlogic.com> wrote:
>>>
>>>>>>> +
>>>>>>> +static struct clk_regmap s4_hdmi_pll_dco = {
>>>>>>> +    .data = &(struct meson_clk_pll_data){
>>>>>>> +        .en = {
>>>>>>> +            .reg_off = ANACTRL_HDMIPLL_CTRL0,
>>>>>>> +            .shift   = 28,
>>>>>>> +            .width   = 1,
>>>>>>> +        },
>>>>>>> +        .m = {
>>>>>>> +            .reg_off = ANACTRL_HDMIPLL_CTRL0,
>>>>>>> +            .shift   = 0,
>>>>>>> +            .width   = 8,
>>>>>>> +        },
>>>>>>> +        .n = {
>>>>>>> +            .reg_off = ANACTRL_HDMIPLL_CTRL0,
>>>>>>> +            .shift   = 10,
>>>>>>> +            .width   = 5,
>>>>>>> +        },
>>>>>>> +        .frac = {
>>>>>>> +            .reg_off = ANACTRL_HDMIPLL_CTRL1,
>>>>>>> +            .shift   = 0,
>>>>>>> +            .width   = 17,
>>>>>>> +        },
>>>>>>> +        .l = {
>>>>>>> +            .reg_off = ANACTRL_HDMIPLL_CTRL0,
>>>>>>> +            .shift   = 31,
>>>>>>> +            .width   = 1,
>>>>>>> +        },
>>>>>>> +        .rst = {
>>>>>>> +            .reg_off = ANACTRL_HDMIPLL_CTRL0,
>>>>>>> +            .shift   = 29,
>>>>>>> +            .width   = 1,
>>>>>>> +        },
>>>>>>> +    },
>>>>>>> +    .hw.init = &(struct clk_init_data){
>>>>>>> +        .name = "hdmi_pll_dco",
>>>>>>> +        .ops = &meson_clk_pll_ro_ops,
>>>>>>> +        .parent_data = (const struct clk_parent_data []) {
>>>>>>> +            { .fw_name = "xtal", }
>>>>>>> +        },
>>>>>>> +        .num_parents = 1,
>>>>>>> +        /*
>>>>>>> +         * Display directly handle hdmi pll registers ATM, we need
>>>>>>> +         * NOCACHE to keep our view of the clock as accurate as
>>>>>>> +         * possible
>>>>>>> +         */
>>>>>>
>>>>>> Is it really ?
>>>>>>
>>>>>> Given that HDMI support for the s4 is there yet, the
>>>>>> addresses have changes and the region is no longer a syscon, it is time
>>>>>> for the HDMI driver to get fixed.
>>>> The HDMI PLL is configured in the Uboot phase and does not change the
>>>> frequency in the kernel phase. So we use the NOCACHE flag and
>>>> "ro_ops".
>>> That's no reason to put NOCACHE or ro-ops
>>> If you want the frequencies to be statically assinged, the correct way
>>> would be through assigned-rate in DT I guess.
>>
>> Okay. You're right. However, when registering with OPS, HDMI PLL will be
>> reset. It takes time for PLL to stabilize the output frequency, which will
>> lead to the startup screen flashing.
>>
>> I would like to know how to solve this problem if not using ro_ops.
>>
>>>
>
> You can add new ops or tweak the current init function.

HDMI PLL is not different from other PLLS, so I think adding OPS is weird.

>
> Safest would be to do the following :
> * Check if the PLLs is already on.
> * Check if the 'pll->init_regs' matches what is already set
> - if so, you can skip the reset
> - if not, you need to reset as usual

static int meson_clk_pll_init(struct clk_hw *hw)

{

struct clk_regmap *clk = to_clk_regmap(hw);

struct meson_clk_pll_data *pll = meson_clk_pll_data(clk);

if (pll->init_count) {

meson_parm_write(clk->map, &pll->rst, 1);

regmap_multi_reg_write(clk->map, pll->init_regs,

| pll->init_count);

meson_parm_write(clk->map, &pll->rst, 0);

}

return 0;

}

Because the init function looks like this. Therefore, HDMI PLL
init_count is not given. Can I change it like this?