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: <ZOxNFPRZI/N3a7Kr@linaro.org>
Date:   Mon, 28 Aug 2023 10:30:28 +0300
From:   Abel Vesa <abel.vesa@...aro.org>
To:     Jagadeesh Kona <quic_jkona@...cinc.com>
Cc:     Konrad Dybcio <konrad.dybcio@...aro.org>,
        "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 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.


> Thanks,
> Jagadeesh
> 
> > Konrad