linux-kernel - Re: [PATCH v2 4/6] clk: qcom: Use HW_CTRL_TRIGGER flag to switch video GDSC to HW mode

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Message-ID: <ecafa01d-f942-4418-a01f-885b431c67ee@linaro.org>
Date:   Sat, 2 Sep 2023 13:59:02 +0200
From:   Konrad Dybcio <konrad.dybcio@...aro.org>
To:     Abel Vesa <abel.vesa@...aro.org>,
        Jagadeesh Kona <quic_jkona@...cinc.com>
Cc:     "Rafael J . Wysocki" <rafael@...nel.org>,
        Kevin Hilman <khilman@...nel.org>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Pavel Machek <pavel@....cz>, Len Brown <len.brown@...el.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Andy Gross <agross@...nel.org>,
        Mike Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>,
        Taniya Das <tdas@....qualcomm.com>, linux-pm@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-arm-msm@...r.kernel.org,
        Ajit Pandey <quic_ajipan@...cinc.com>,
        Imran Shaik <quic_imrashai@...cinc.com>
Subject: Re: [PATCH v2 4/6] clk: qcom: Use HW_CTRL_TRIGGER flag to switch
 video GDSC to HW mode

On 28.08.2023 09:30, Abel Vesa wrote:
> On 23-08-28 12:18:30, Jagadeesh Kona wrote:
>>
>>
>> On 8/26/2023 4:17 PM, Konrad Dybcio wrote:
>>> On 23.08.2023 12:41, Abel Vesa wrote:
>>>> On 23-08-16 19:56:46, Konrad Dybcio wrote:
>>>>> On 16.08.2023 16:57, Abel Vesa wrote:
>>>>>> From: Jagadeesh Kona <quic_jkona@...cinc.com>
>>>>>>
>>>>>> The current HW_CTRL flag switches the video GDSC to HW control mode as
>>>>>> part of GDSC enable itself, instead of that use HW_CTRL_TRIGGER flag to
>>>>>> give consumer drivers more control and switch the GDSC mode as and when
>>>>>> required.
>>>>>>
>>>>>> HW_CTRL_TRIGGER flag allows consumer drivers to switch the video GDSC to
>>>>>> HW/SW control modes at runtime using dev_pm_genpd_set_hwmode API.
>>>>>>
>>>>>> Signed-off-by: Jagadeesh Kona <quic_jkona@...cinc.com>
>>>>>> Signed-off-by: Abel Vesa <abel.vesa@...aro.org>
>>>>>> ---
>>>>> Do we have any use for the HW_CTRL flag?
>>>>>
>>>>> Perhaps it should be renamed to HW_CTRL_ALWAYS?
>>>>>
>>>>> Or even better, *if and only if* that is necessary, add a common
>>>>> property like "always_hw_managed" to the genpd code?
>>>>
>>>> The HW_CTRL flag is still needed for the consumers that expect the GDSC
>>>> to be have the HW control bit set right after it gets enabled.
>>> Guess the correct question here would be.. Are there any?
>>>
>>
>> Yes, Display GDSC(mdss_gdsc) is required to be controlled always in HW
>> control mode when it is enabled.
>>
> 
> Actually, since all the GDSCs that support HW control are by default
> switched to HW mode after they are enabled, we can't make any changes
> with respect to that since we risk breaking consumers. Therefore, the
> new flag makes perfect sense since we can switch GDSCs from HW_CTRL to
> HW_CTRL_TRIGGER per platform/consumer.
Ok, I can get behind this reasoning.

The flag name gives me a little 'eeh' feeling, but I can't
think of anything much better either..

Acked-by: Konrad Dybcio <konrad.dybcio@...aro.org>

Konrad