Re: [PATCH V6 3/3] clk: meson: s4: add support for Amlogic S4 SoC peripheral clock controller

Yu Tu
2023-01-30T10:01:07Z

On 2023/1/30 17:47, Jerome Brunet wrote:
> [ EXTERNAL EMAIL ]
>
>
> On Mon 30 Jan 2023 at 17:41, Yu Tu <yu.tu@amlogic.com> wrote:
>
>> On 2023/1/30 17:06, Jerome Brunet wrote:
>>> [ EXTERNAL EMAIL ]
>>> On Sat 28 Jan 2023 at 18:17, Yu Tu <yu.tu@amlogic.com> wrote:
>>>
>>>> On 2023/1/20 17:47, Jerome Brunet wrote:
>>>>> [ EXTERNAL EMAIL ]
>>>>> On Fri 20 Jan 2023 at 11:33, Yu Tu <yu.tu@amlogic.com> wrote:
>>>>>
>>>>>> Hi
>>>>>> On 2023/1/19 19:37, Jerome Brunet wrote:
>>>>>>> [ EXTERNAL EMAIL ]
>>>>>>> On Mon 16 Jan 2023 at 15:42, Yu Tu <yu.tu@amlogic.com> wrote:
>>>>>>>
>>>>>>>> Add the peripherals clock controller driver in the s4 SoC family.
>>>>>>>>
>>>>>>>> Signed-off-by: Yu Tu <yu.tu@amlogic.com>
>>>>>>> [...]
>>>>>>>
>>>>>>>> +
>>>>>>>> +/* Video Clocks */
>>>>>>>> +static struct clk_regmap s4_vid_pll_div = {
>>>>>>>> + .data = &(struct meson_vid_pll_div_data){
>>>>>>>> + .val = {
>>>>>>>> + .reg_off = CLKCTRL_VID_PLL_CLK_DIV,
>>>>>>>> + .shift = 0,
>>>>>>>> + .width = 15,
>>>>>>>> + },
>>>>>>>> + .sel = {
>>>>>>>> + .reg_off = CLKCTRL_VID_PLL_CLK_DIV,
>>>>>>>> + .shift = 16,
>>>>>>>> + .width = 2,
>>>>>>>> + },
>>>>>>>> + },
>>>>>>>> + .hw.init = &(struct clk_init_data) {
>>>>>>>> + .name = "vid_pll_div",
>>>>>>>> + /*
>>>>>>>> + * The frequency division from the hdmi_pll clock to the vid_pll_div
>>>>>>>> + * clock is the default value of this register. When designing the
>>>>>>>> + * video module of the chip, a default value that can meet the
>>>>>>>> + * requirements of the video module will be solidified according
>>>>>>>> + * to the usage requirements of the chip, so as to facilitate chip
>>>>>>>> + * simulation. So this is ro_ops.
>>>>>>>> + * It is important to note that this clock is not used on this
>>>>>>>> + * chip and is described only for the integrity of the clock tree.
>>>>>>>> + */
>>>>>>> If it is reset value and will be applicable to all the design, regarless
>>>>>>> of the use-case, then yes RO ops is OK
>>>>>>>
>>>>>>> >From what I understand here, the value will depend on the use-case requirements.
>>>>>>> This is a typical case where the DT prop "assigned-rate" should be used, not RO ops.
>>>>>>
>>>>>> Check the previous chip history, the actual scene is not used at all,
>>>>>> basically is used in simulation. So the previous SOC was "ro_ops" without
>>>>>> any problems. This S4 SOC is not actually useful either.
>>>>>>
>>>>>> So when you were upstream, you had no problem making "ro_ops". I wonder if
>>>>>> I could delete this useless clock, so you don't have to worry about it.
>>>>> I don't know what to make of this. What is the point of adding a useless
>>>>> clock ?
>>>>
>>>> As explained earlier this "vid_pll_div" is actually used in chip
>>>> emulation. So next I'd like to know what you suggest to do with the clock?
>>>>
>>> If it does not exist in the actual SoC, please remove it
>>>
>>
>> If I remove it, the "vid_pll_sel" clock will be missing a parent
>> (vid_pll_div). I will use the table method and give the above reasons. Do
>> you accept this method?
>
> Either the clock exists or it does not.
>
> If the HW actually exist, it is expected to be properly described.
> If it does not, it obviously cannot be an input to another clock.
>
> Please sort this out and make the necessary changes.
>

The CLKCTRL_VID_PLL_CLK_DIV register is actually described, but it is
not used in the actual board. According to your reply just now,
description is required, but I want to know how to describe it to meet
your requirements.

Please give me some suggestions.