linux-kernel - Re: [PATCH V2 RESEND 6/6] arm64: dts: qcom: sm8650: Add video and camera clock controllers

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Message-ID: <03f8d2ee-2467-48aa-9b76-06eb13202b8c@quicinc.com>
Date: Fri, 5 Apr 2024 11:30:59 +0530
From: Jagadeesh Kona <quic_jkona@...cinc.com>
To: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
CC: Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio
	<konrad.dybcio@...aro.org>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>, Rob Herring <robh+dt@...nel.org>,
        "Krzysztof
 Kozlowski" <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley
	<conor+dt@...nel.org>,
        Vladimir Zapolskiy <vladimir.zapolskiy@...aro.org>,
        <linux-arm-msm@...r.kernel.org>, <linux-clk@...r.kernel.org>,
        <devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        Taniya Das
	<quic_tdas@...cinc.com>,
        Satya Priya Kakitapalli <quic_skakitap@...cinc.com>,
        Ajit Pandey <quic_ajipan@...cinc.com>,
        Imran Shaik
	<quic_imrashai@...cinc.com>
Subject: Re: [PATCH V2 RESEND 6/6] arm64: dts: qcom: sm8650: Add video and
 camera clock controllers



On 4/4/2024 9:35 PM, Dmitry Baryshkov wrote:
> On Thu, 4 Apr 2024 at 13:06, Jagadeesh Kona <quic_jkona@...cinc.com> wrote:
>>
>>
>>
>> On 4/4/2024 11:00 AM, Dmitry Baryshkov wrote:
>>> On Thu, 4 Apr 2024 at 08:13, Jagadeesh Kona <quic_jkona@...cinc.com> wrote:
>>>>
>>>>
>>>>
>>>> On 4/3/2024 9:24 PM, Dmitry Baryshkov wrote:
>>>>> On Wed, 3 Apr 2024 at 10:16, Jagadeesh Kona <quic_jkona@...cinc.com> wrote:
>>>>>>
>>>>>>
>>>>>>
>>>>>> On 3/25/2024 11:38 AM, Jagadeesh Kona wrote:
>>>>>>>
>>>>>>>
>>>>>>> On 3/21/2024 6:43 PM, Dmitry Baryshkov wrote:
>>>>>>>> On Thu, 21 Mar 2024 at 11:27, Jagadeesh Kona <quic_jkona@...cinc.com>
>>>>>>>> wrote:
>>>>>>>>>
>>>>>>>>> Add device nodes for video and camera clock controllers on Qualcomm
>>>>>>>>> SM8650 platform.
>>>>>>>>>
>>>>>>>>> Signed-off-by: Jagadeesh Kona <quic_jkona@...cinc.com>
>>>>>>>>> ---
>>>>>>>>>      arch/arm64/boot/dts/qcom/sm8650.dtsi | 28 ++++++++++++++++++++++++++++
>>>>>>>>>      1 file changed, 28 insertions(+)
>>>>>>>>>
>>>>>>>>> diff --git a/arch/arm64/boot/dts/qcom/sm8650.dtsi
>>>>>>>>> b/arch/arm64/boot/dts/qcom/sm8650.dtsi
>>>>>>>>> index 32c0a7b9aded..d862aa6be824 100644
>>>>>>>>> --- a/arch/arm64/boot/dts/qcom/sm8650.dtsi
>>>>>>>>> +++ b/arch/arm64/boot/dts/qcom/sm8650.dtsi
>>>>>>>>> @@ -4,6 +4,8 @@
>>>>>>>>>       */
>>>>>>>>>
>>>>>>>>>      #include <dt-bindings/clock/qcom,rpmh.h>
>>>>>>>>> +#include <dt-bindings/clock/qcom,sm8450-videocc.h>
>>>>>>>>> +#include <dt-bindings/clock/qcom,sm8650-camcc.h>
>>>>>>>>>      #include <dt-bindings/clock/qcom,sm8650-dispcc.h>
>>>>>>>>>      #include <dt-bindings/clock/qcom,sm8650-gcc.h>
>>>>>>>>>      #include <dt-bindings/clock/qcom,sm8650-gpucc.h>
>>>>>>>>> @@ -3110,6 +3112,32 @@ opp-202000000 {
>>>>>>>>>                             };
>>>>>>>>>                     };
>>>>>>>>>
>>>>>>>>> +               videocc: clock-controller@...0000 {
>>>>>>>>> +                       compatible = "qcom,sm8650-videocc";
>>>>>>>>> +                       reg = <0 0x0aaf0000 0 0x10000>;
>>>>>>>>> +                       clocks = <&bi_tcxo_div2>,
>>>>>>>>> +                                <&gcc GCC_VIDEO_AHB_CLK>;
>>>>>>>>> +                       power-domains = <&rpmhpd RPMHPD_MMCX>;
>>>>>>>>> +                       required-opps = <&rpmhpd_opp_low_svs>;
>>>>>>>>
>>>>>>>> The required-opps should no longer be necessary.
>>>>>>>>
>>>>>>>
>>>>>>> Sure, will check and remove this if not required.
>>>>>>
>>>>>>
>>>>>> I checked further on this and without required-opps, if there is no vote
>>>>>> on the power-domain & its peer from any other consumers, when runtime
>>>>>> get is called on device, it enables the power domain just at the minimum
>>>>>> non-zero level. But in some cases, the minimum non-zero level of
>>>>>> power-domain could be just retention and is not sufficient for clock
>>>>>> controller to operate, hence required-opps property is needed to specify
>>>>>> the minimum level required on power-domain for this clock controller.
>>>>>
>>>>> In which cases? If it ends up with the retention vote, it is a bug
>>>>> which must be fixed.
>>>>>
>>>>
>>>> The minimum non-zero level(configured from bootloaders) of MMCX is
>>>> retention on few chipsets but it can vary across the chipsets. Hence to
>>>> be on safer side from our end, it is good to have required-opps in DT to
>>>> specify the minimum level required for this clock controller.
>>>
>>> We are discussing sm8650, not some abstract chipset. Does it list
>>> retention or low_svs as a minimal level for MMCX?
>>>
>>
>> Actually, the minimum level for MMCX is external to the clock
>> controllers.
> 
> Yes, it comes from cmd-db
> 
>>   But the clock controller requires MMCX to be atleast at
>> lowsvs for it to be functional.
> 
> Correct
> 
>> Hence we need to keep required-opps to
>> ensure the same without relying on the actual minimum level for MMCX.
> 
> And this is not correct. There is no need for the DT to be redundant.
> I plan to send patches removing the existing required-opps when they
> are not required.
>
I agree this is not required if cmd-db minimum level is already at 
lowsvs. But since MMCX running at lowsvs is a mandatory requirement for 
clock controller to operate, I believe it is good to have required-opps 
to ensure we meet this requirement in all cases, rather than relying on 
the cmd-db minimum level which we have no control over.

Thanks,
Jagadeesh