linux-kernel - Re: [PATCH 4/5] clk: qcom: Add camera clock controller driver for SM8150

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Message-ID: <c892f773-7716-4736-3499-5c8254e3618e@quicinc.com>
Date: Fri, 8 Mar 2024 18:10:13 +0530
From: "Satya Priya Kakitapalli (Temp)" <quic_skakitap@...cinc.com>
To: Bryan O'Donoghue <bryan.odonoghue@...aro.org>,
        Bjorn Andersson
	<andersson@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        "Michael
 Turquette" <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>, Abhishek Sahu <absahu@...eaurora.org>,
        Rob Herring <robh@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley
	<conor+dt@...nel.org>
CC: Stephen Boyd <sboyd@...eaurora.org>, <linux-arm-msm@...r.kernel.org>,
        <linux-clk@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <devicetree@...r.kernel.org>, Ajit Pandey <quic_ajipan@...cinc.com>,
        "Imran
 Shaik" <quic_imrashai@...cinc.com>,
        Taniya Das <quic_tdas@...cinc.com>,
        Jagadeesh Kona <quic_jkona@...cinc.com>
Subject: Re: [PATCH 4/5] clk: qcom: Add camera clock controller driver for
 SM8150


On 3/8/2024 4:29 PM, Bryan O'Donoghue wrote:
> On 08/03/2024 10:58, Bryan O'Donoghue wrote:
>> On 08/03/2024 10:46, Satya Priya Kakitapalli (Temp) wrote:
>>>>
>>>> Not if you mark it critical
>>>>
>>>
>>> Marking the clock as critical keeps the associated power domain 
>>> always-on which impacts power. For this reason we are not using 
>>> CLK_IS_CRITICAL and instead making them always on from probe.
>>
>> How does the clock do anything _useful_ if the power-domain gets 
>> switched off ?
>>
>> ---
>> bod
>
> i.e. the clock can't be running "always-on" if it has no power..
>

If BIT(0) is set from probe, during any active usecase, the clock gets 
turned ON automatically when the power domain is turned ON.

But when we use CLK_IS_CRITICAL flag, the framework keeps the power 
domain ON and doesn't let the power domain to turn off even when there 
is no active usecase.