linux-kernel - Re: [PATCH 2/3] clk: qcom: gcc-sm8150: Add gcc_parents_0

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Date: Mon, 5 Feb 2024 14:07:48 +0530
From: "Satya Priya Kakitapalli (Temp)" <quic_skakitap@...cinc.com>
To: Konrad Dybcio <konrad.dybcio@...aro.org>,
        Bjorn Andersson
	<andersson@...nel.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>,
        Taniya Das <quic_tdas@...cinc.com>
CC: <linux-arm-msm@...r.kernel.org>, <linux-clk@...r.kernel.org>,
        <devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        Ajit Pandey
	<quic_ajipan@...cinc.com>,
        Imran Shaik <quic_imrashai@...cinc.com>,
        "Jagadeesh Kona" <quic_jkona@...cinc.com>
Subject: Re: [PATCH 2/3] clk: qcom: gcc-sm8150: Add gcc_parents_0_ao support


On 1/25/2024 3:25 PM, Konrad Dybcio wrote:
>
>
> On 1/25/24 06:49, Satya Priya Kakitapalli (Temp) wrote:
>>
>> On 1/23/2024 11:17 PM, Konrad Dybcio wrote:
>>>
>>>
>>> On 1/23/24 17:34, Satya Priya Kakitapalli wrote:
>>>> Add active_only support for gcc_parents_0, this is needed because
>>>> some of the clocks under it are critical which would vote on xo
>>>> blocking the suspend.
>>>>
>>>> Signed-off-by: Satya Priya Kakitapalli <quic_skakitap@...cinc.com>
>>>> ---
>>>
>>> Is there a need to keep gcc_cpuss_ahb_clk_src around? Do we do any
>>> ratesetting on it? Should we ever turn it off?
>>>
>>
>> The branch clocks under gcc_cpuss_ahb_clk_src are critical clocks, 
>> which are running at 19.2Mhz causing vote on XO during suspend. As of 
>> now no rate setting is happening but this rcg is useful to get the 
>> exact rates from debugfs. Hence this change is needed to avoid XO 
>> shutdown issues.
>
> So, if I underderstood you correctly, this clock serves no purpose other
> than getting rate?
>
> In this case, I'd say we should de-register it from the clock driver and
> use debugcc [1] (contributions welcome!) for precise measurements.
>

Although currently there is no rate-setting happening now, its better to 
keep the rcg modelling as is, considering that it might be needed if 
some use case arises in future.