linux-kernel - Re: [PATCH RFT v2 01/14] dt-bindings: clock: qcom,rpmcc: Add a way to enable unused clock cleanup

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Date:   Fri, 7 Apr 2023 22:17:18 +0200
From:   Konrad Dybcio <konrad.dybcio@...aro.org>
To:     Stephen Boyd <sboyd@...nel.org>, Rob Herring <robh@...nel.org>
Cc:     Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Michael Turquette <mturquette@...libre.com>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        linux-arm-msm@...r.kernel.org, linux-clk@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
        devicetree@...r.kernel.org
Subject: Re: [PATCH RFT v2 01/14] dt-bindings: clock: qcom,rpmcc: Add a way to
 enable unused clock cleanup



On 6.04.2023 16:44, Konrad Dybcio wrote:
> 
> 
> On 17.03.2023 19:20, Stephen Boyd wrote:
>> Quoting Konrad Dybcio (2023-03-16 17:31:34)
>>>
>>> On 16.03.2023 23:58, Rob Herring wrote:
>>>> On Wed, Mar 08, 2023 at 10:35:17PM +0100, Konrad Dybcio wrote:
>>>>>  
>>>>> +  qcom,clk-disable-unused:
>>>>> +    type: boolean
>>>>> +    description:
>>>>> +      Indicates whether unused RPM clocks can be shut down with the common
>>>>> +      unused clock cleanup. Requires a functional interconnect driver.
>>>>
>>>> I don't think this should be QCom specific. Come up with something 
>>>> common (which will probably have some debate). 
>>> Generally the opposite (ignoring unused clocks during the cleanup) is
>>> the thing you need to opt into.
>>>
>>> I can however see how (especially with the focus on not breaking things
>>> for older DTs) somebody else may also decide to only allow them to be
>>> cleaned up conditionally (by marking the clocks that were enabled earlier
>>> as enabled in Linux OR not addding clk.flags |= CLK_IGNORE_UNUSED) as we
>>> do here.
>>>
>>> Stephen, Rob, would `clk-disable-unused` be a fitting generic property
>>> name for that? Should we also think about `clk-ignore-unused` as a
>>> clock-controller-specific alternative to the CCF-wide clk_ignore_unused
>>> cmdline?
>>>
>>
>> There are multiple threads on the list about disabling unused clks.
>> Moving the decision to disable unused clks to a DT property is yet
>> another approach. I'd rather not do that, because it really isn't
>> describing the hardware configuration. If anything, I'd expect the
>> property to be describing which clks are enabled by the firmware and
>> then leave the decision to disable them because they're unused up to the
>> software.
> After some more thinking, I realized that this could be made opt-in
> simply with driver_data..
> 
> WDYT?
..on a re-evaluation, obviously not a great idea.. Old DTBs will not
be happy about that.

Konrad
> 
> Konrad