linux-kernel - Re: [PATCH] arm64: dts: qcom: qcs6490-rb3gen2: Declare GCC clocks protected

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Message-ID: <20240209184046.GB2936378@hu-bjorande-lv.qualcomm.com>
Date: Fri, 9 Feb 2024 10:40:46 -0800
From: Bjorn Andersson <quic_bjorande@...cinc.com>
To: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
CC: Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio
	<konrad.dybcio@...aro.org>,
        Rob Herring <robh@...nel.org>,
        "Krzysztof
 Kozlowski" <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley
	<conor+dt@...nel.org>,
        Taniya Das <quic_tdas@...cinc.com>, <linux-arm-msm@...r.kernel.org>,
        <devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] arm64: dts: qcom: qcs6490-rb3gen2: Declare GCC clocks
 protected

On Fri, Feb 09, 2024 at 08:01:15PM +0200, Dmitry Baryshkov wrote:
> On Fri, 9 Feb 2024 at 18:21, Bjorn Andersson <quic_bjorande@...cinc.com> wrote:
> >
> > The SC7180 GCC binding describes clocks which, due to the difference in
> > security model, are not accessible on the RB3gen2 - in the same way seen
> > on QCM6490.
> >
> > Mark these clocks as protected, to allow the board to boot.
> >
> > Signed-off-by: Bjorn Andersson <quic_bjorande@...cinc.com>
> > ---
> > I did notice Taniya's patch [1] after writing this patch. I'd prefer to
> > merge this minimal set asap, to make the board boot, unless there's a
> > strong argument for including those other clocks in the protected list.
> >
> > [1] https://lore.kernel.org/linux-arm-msm/20240208062836.19767-6-quic_tdas@quicinc.com/
> > ---
> >  arch/arm64/boot/dts/qcom/qcs6490-rb3gen2.dts | 18 ++++++++++++++++++
> >  1 file changed, 18 insertions(+)
> >
> > diff --git a/arch/arm64/boot/dts/qcom/qcs6490-rb3gen2.dts b/arch/arm64/boot/dts/qcom/qcs6490-rb3gen2.dts
> > index 8bb7d13d85f6..97b1586f9f19 100644
> > --- a/arch/arm64/boot/dts/qcom/qcs6490-rb3gen2.dts
> > +++ b/arch/arm64/boot/dts/qcom/qcs6490-rb3gen2.dts
> > @@ -413,6 +413,24 @@ vreg_bob_3p296: bob {
> >         };
> >  };
> >
> > +&gcc {
> > +       protected-clocks = <GCC_CFG_NOC_LPASS_CLK>,
> > +                          <GCC_EDP_CLKREF_EN>,
> 
> I'd say these two clocks looks strange in this list, but you probably
> know what you are doing. Thus:
> 

Perhaps I wasn't clear enough in the commit message, I took this list
from one of the QCM6490 devices, as it seemed reasonable. I wondered
about this entry, but didn't pay enough attention and didn't test
without it.

But you're obviously correct, it would be very weird, in particular
considering that the board exposes &mdss_edp on a physical connector.

Sure enough, not only is it accessible, I hacked up a patch for enabling
DisplayPort (on &mdss_edp) and as expected it doesn't work without
GCC_EDP_CLKREF_EN.

> Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
> 

Taking the liberty to carry this into v2.

Thank you,
Bjorn

> > +                          <GCC_MSS_CFG_AHB_CLK>,
> > +                          <GCC_MSS_GPLL0_MAIN_DIV_CLK_SRC>,
> > +                          <GCC_MSS_OFFLINE_AXI_CLK>,
> > +                          <GCC_MSS_Q6SS_BOOT_CLK_SRC>,
> > +                          <GCC_MSS_Q6_MEMNOC_AXI_CLK>,
> > +                          <GCC_MSS_SNOC_AXI_CLK>,
> > +                          <GCC_QSPI_CNOC_PERIPH_AHB_CLK>,
> > +                          <GCC_QSPI_CORE_CLK>,
> > +                          <GCC_QSPI_CORE_CLK_SRC>,
> > +                          <GCC_SEC_CTRL_CLK_SRC>,
> > +                          <GCC_WPSS_AHB_BDG_MST_CLK>,
> > +                          <GCC_WPSS_AHB_CLK>,
> > +                          <GCC_WPSS_RSCP_CLK>;
> > +};
> > +
> >  &qupv3_id_0 {
> >         status = "okay";
> >  };
> >
> > ---
> > base-commit: b1d3a0e70c3881d2f8cf6692ccf7c2a4fb2d030d
> > change-id: 20240209-qcm6490-gcc-protected-clocks-ee5fafdb76b3
> >
> > Best regards,
> > --
> > Bjorn Andersson <quic_bjorande@...cinc.com>
> >
> 
> 
> -- 
> With best wishes
> Dmitry