Re: [PATCH v3 2/3] clk: qcom: dispcc-sm8650: add missing CLK_SET_RATE_PARENT flag

[Konrad Dybcio <konrad.dybcio@linaro.org>]

On 17.07.2024 11:49 AM, Dmitry Baryshkov wrote:
> On Wed, 17 Jul 2024 at 12:47, Konrad Dybcio <konrad.dybcio@linaro.org> wrote:
>>
>> On 16.07.2024 6:46 PM, Dmitry Baryshkov wrote:
>>> On Tue, Jul 16, 2024 at 03:46:24PM GMT, neil.armstrong@linaro.org wrote:
>>>> On 16/07/2024 15:44, Dmitry Baryshkov wrote:
>>>>> On Tue, 16 Jul 2024 at 15:32, Neil Armstrong <neil.armstrong@linaro.org> wrote:
>>>>>>
>>>>>> On 16/07/2024 13:20, Dmitry Baryshkov wrote:
>>>>>>> On Tue, Jul 16, 2024 at 11:05:22AM GMT, Neil Armstrong wrote:
>>>>>>>> Add the missing CLK_SET_RATE_PARENT for the byte0_div_clk_src
>>>>>>>> and byte1_div_clk_src, the clock rate should propagate to
>>>>>>>> the corresponding _clk_src.
>>>>>>>>
>>>>>>>> Fixes: 9e939f008338 ("clk: qcom: add the SM8650 Display Clock Controller driver")
>>>>>>>> Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
>>>>>>>> Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>
>>>>>>>> ---
>>>>>>>>    drivers/clk/qcom/dispcc-sm8650.c | 2 ++
>>>>>>>>    1 file changed, 2 insertions(+)
>>>>>>>
>>>>>>> This doesn't seem correct, the byte1_div_clk_src is a divisor, so the
>>>>>>> rate should not be propagated. Other platforms don't set this flag.
>>>>>>>
>>>>>>
>>>>>> Why not ? the disp_cc_mdss_byte1_clk_src has CLK_SET_RATE_PARENT and a div_table,
>>>>>> and we only pass DISP_CC_MDSS_BYTE1_CLK to the dsi controller.
>>>>>
>>>>> Yes, the driver sets byte_clk with the proper rate, then it sets
>>>>> byte_intf_clk, which results in a proper divisor.
>>>>> If we have CLK_SET_RATE_PARENT for byte1_div_clk_src, then setting
>>>>> byte_intf_clk rate will also result in a rate change for the byte_clk
>>>>> rate.
>>>>>
>>>>> Note, all other platforms don't set that flag for this reason (I think
>>>>> I had to remove it during sm8450 development for this reason).
>>>>>
>>>>
>>>> Ack, I think this deserves a comment explaining this, I'll add it.
>>>
>>> But where to place it? This applies to _all_ dispcc controllers.
>>
>> Commit message
> 
> It is already committed.

You can mention in it the message of this patch.

Konrad