linux-kernel - Re: [PATCH v3 02/21] arm64: dts: qcom: msm8939: correct sleep clock frequency

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Message-ID: <CAA8EJpp1a=qpc-0OVQWeLvbndyTGv6oXPU1FiM9rgV6q_i=XxA@mail.gmail.com>
Date: Mon, 30 Dec 2024 16:10:59 +0200
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: "Bryan O'Donoghue" <bryan.odonoghue@...aro.org>
Cc: Bjorn Andersson <andersson@...nel.org>, Konrad Dybcio <konradybcio@...nel.org>, 
	Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, 
	Leo Yan <leo.yan@...ux.dev>, Georgi Djakov <djakov@...nel.org>, Shawn Guo <shawn.guo@...aro.org>, 
	Stephan Gerhold <stephan@...hold.net>, Zac Crosby <zac@...areup.com>, Bastian Köcher <git@...r.de>, 
	Jeremy McNicoll <jeremymc@...hat.com>, Rohit Agarwal <quic_rohiagar@...cinc.com>, 
	Melody Olvera <quic_molvera@...cinc.com>, cros-qcom-dts-watchers@...omium.org, 
	Stephen Boyd <swboyd@...omium.org>, Rajendra Nayak <quic_rjendra@...cinc.com>, 
	Martin Botka <martin.botka@...ainline.org>, Jonathan Marek <jonathan@...ek.ca>, 
	Vinod Koul <vkoul@...nel.org>, Tengfei Fan <quic_tengfan@...cinc.com>, 
	Fenglin Wu <quic_fenglinw@...cinc.com>, Neil Armstrong <neil.armstrong@...aro.org>, 
	Abel Vesa <abel.vesa@...aro.org>, Alexandru Marc Serdeliuc <serdeliuk@...oo.com>, 
	Vladimir Zapolskiy <vladimir.zapolskiy@...aro.org>, Sibi Sankar <quic_sibis@...cinc.com>, 
	Jun Nie <jun.nie@...aro.org>, Max Chen <mchen@...areup.com>, 
	Vincent Knecht <vincent.knecht@...loo.org>, 
	Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>, linux-arm-msm@...r.kernel.org, 
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 02/21] arm64: dts: qcom: msm8939: correct sleep clock frequency

On Mon, 30 Dec 2024 at 11:49, Bryan O'Donoghue
<bryan.odonoghue@...aro.org> wrote:
>
> On 24/12/2024 10:17, Dmitry Baryshkov wrote:
> > The MSM8939 platform uses PM8916 to provide sleep clock. According to the
> > documentation, that clock has 32.7645 kHz frequency. Correct the sleep
> > clock definition.
> >
> > Fixes: 61550c6c156c ("arm64: dts: qcom: Add msm8939 SoC")
> > Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
> > ---
> >   arch/arm64/boot/dts/qcom/msm8939.dtsi | 2 +-
> >   1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/arch/arm64/boot/dts/qcom/msm8939.dtsi b/arch/arm64/boot/dts/qcom/msm8939.dtsi
> > index 7a6f1eeaa3fc438f7b6c1d3b2dd17fb1b6f81d9a..7cd5660de1b33def5b9dc8a0d02583c3eaffb17f 100644
> > --- a/arch/arm64/boot/dts/qcom/msm8939.dtsi
> > +++ b/arch/arm64/boot/dts/qcom/msm8939.dtsi
> > @@ -34,7 +34,7 @@ xo_board: xo-board {
> >               sleep_clk: sleep-clk {
> >                       compatible = "fixed-clock";
> >                       #clock-cells = <0>;
> > -                     clock-frequency = <32768>;
> > +                     clock-frequency = <32764>;
> >               };
> >       };
> >
> >
>
> Here's a quote from "MSM8936/MSM8939 Clock Plan"
> Section 2.1:
>
> "The chip does not have a separate sleep crystal. The sleep clock, whose
> oscillation frequency is 32.768 kHz, used as the source for timetick is
> generated from XO using a divisor of 586."

19200000 / 586 = 32764.5


-- 
With best wishes
Dmitry