linux-kernel - Re: [PATCH 2/7] clk: qcom: Add Global Clock Controller driver for IPQ9574

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Message-ID: <d73f0eec-6e02-e72f-79d7-2c56245f7651@linaro.org>
Date:   Tue, 24 Jan 2023 10:53:35 +0100
From:   Konrad Dybcio <konrad.dybcio@...aro.org>
To:     Devi Priya <quic_devipriy@...cinc.com>, agross@...nel.org,
        andersson@...nel.org, robh+dt@...nel.org,
        krzysztof.kozlowski+dt@...aro.org, mturquette@...libre.com,
        sboyd@...nel.org, linus.walleij@...aro.org,
        catalin.marinas@....com, will@...nel.org, p.zabel@...gutronix.de,
        shawnguo@...nel.org, arnd@...db.de, marcel.ziswiler@...adex.com,
        dmitry.baryshkov@...aro.org, nfraprado@...labora.com,
        broonie@...nel.org, tdas@...eaurora.org,
        linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-clk@...r.kernel.org,
        linux-gpio@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Cc:     quic_srichara@...cinc.com, quic_gokulsri@...cinc.com,
        quic_sjaganat@...cinc.com, quic_kathirav@...cinc.com,
        quic_arajkuma@...cinc.com, quic_anusha@...cinc.com,
        quic_poovendh@...cinc.com
Subject: Re: [PATCH 2/7] clk: qcom: Add Global Clock Controller driver for
 IPQ9574



On 24.01.2023 08:27, Devi Priya wrote:
> 
> 
> On 1/13/2023 7:39 PM, Konrad Dybcio wrote:
>>
>>
>> On 13.01.2023 14:21, Devi Priya wrote:
>>>
>>>
>>> On 1/10/2023 6:07 PM, Konrad Dybcio wrote:
>>>>
>>>>
>>>> On 10.01.2023 13:13, devi priya wrote:
>>>>> Add Global Clock Controller (GCC) driver for ipq9574 based devices
>>>>>
>>>>> Co-developed-by: Anusha Rao <quic_anusha@...cinc.com>
>>>>> Signed-off-by: Anusha Rao <quic_anusha@...cinc.com>
>>>>> Signed-off-by: devi priya <quic_devipriy@...cinc.com>
>>>>> ---
>> [...]
>>
>>>>> +static struct clk_branch gcc_blsp1_qup6_i2c_apps_clk = {
>>>>> +    .halt_reg = 0x07024,
>>>>> +    .clkr = {
>>>>> +        .enable_reg = 0x07024,
>>>>> +        .enable_mask = BIT(0),
>>>>> +        .hw.init = &(struct clk_init_data) {
>>>>> +            .name = "gcc_blsp1_qup6_i2c_apps_clk",
>>>>> +            .parent_hws = (const struct clk_hw *[]) {
>>>>> +                    &blsp1_qup6_i2c_apps_clk_src.clkr.hw },
>>>>> +            .num_parents = 1,
>>>>> +            .flags = CLK_SET_RATE_PARENT | CLK_IGNORE_UNUSED,
>>>> Sounds very much like a hack..
>>> Got it, will remove the clock entry as it is not being used in linux
>> I'm not sure removing it is the best option, somebody might have a
>> funky board where they use this particular QUP for I2C for whatever
>> reason and then the clock would have to be re-added..
> Sure, Understood
> This clock is used by the RPM component to communicate with PMIC and we
> would add the critical flag here
Okay, so this SoC is intended to ship with some RPM PMICs and
*always* with an I2C companion that's required for some basic
functionality, correct?

Otherwise, if it's just for wifi/multimedia/etc (like PM8008ij
on some newer devices), you should not make it critical and
simply rely on Linux keeping it alive like so:

consumer takes a regulator
the regulator does not go to sleep because it's consumed
the PMIC is active because a regulator on it is being used
the I2C bus is active because its child PMIC is used
the I2C clocks are alive because there's an active user

Konrad
> 
>> Thanks for addressing all of the review comments so thoroughly!
>>
>> Konrad
> 
> Best Regards,
> Devi Priya