linux-kernel - Re: [PATCH 1/3] arm: dts: qcom: apq8064: Use 27MHz PXO clock as DSI PLL reference

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Message-ID: <CAA8EJprQ03ipZzO+1vgt9W7jFbLXgsYR0n-oJxVB-142x8dgRA@mail.gmail.com>
Date:   Mon, 30 Aug 2021 04:18:39 +0300
From:   Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To:     Marijn Suijten <marijn.suijten@...ainline.org>
Cc:     phone-devel@...r.kernel.org, ~postmarketos/upstreaming@...ts.sr.ht,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...ainline.org>,
        Konrad Dybcio <konrad.dybcio@...ainline.org>,
        Martin Botka <martin.botka@...ainline.org>,
        Jami Kettunen <jami.kettunen@...ainline.org>,
        Pavel Dubrova <pashadubrova@...il.com>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Andy Gross <agross@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        "open list:DRM DRIVER FOR MSM ADRENO GPU" 
        <linux-arm-msm@...r.kernel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/3] arm: dts: qcom: apq8064: Use 27MHz PXO clock as DSI
 PLL reference

On Sun, 29 Aug 2021 at 23:30, Marijn Suijten
<marijn.suijten@...ainline.org> wrote:
>
> The 28NM DSI PLL driver for msm8960 calculates with a 27MHz reference
> clock and should hence use PXO, not CXO which runs at 19.2MHz.
>
> Note that none of the DSI PHY/PLL drivers currently use this "ref"
> clock; they all rely on (sometimes inexistant) global clock names and
> usually function normally without a parent clock.  This discrepancy will
> be corrected in a future patch, for which this change needs to be in
> place first.
>
> Cc: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
> Signed-off-by: Marijn Suijten <marijn.suijten@...ainline.org>

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

Checked the downstream driver, it always uses 27 MHz clock in calculations.

> ---
>  arch/arm/boot/dts/qcom-apq8064.dtsi | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/arch/arm/boot/dts/qcom-apq8064.dtsi b/arch/arm/boot/dts/qcom-apq8064.dtsi
> index 2687c4e890ba..77659b783759 100644
> --- a/arch/arm/boot/dts/qcom-apq8064.dtsi
> +++ b/arch/arm/boot/dts/qcom-apq8064.dtsi
> @@ -198,7 +198,7 @@ cxo_board: cxo_board {
>                         clock-frequency = <19200000>;
>                 };
>
> -               pxo_board {
> +               pxo_board: pxo_board {
>                         compatible = "fixed-clock";
>                         #clock-cells = <0>;
>                         clock-frequency = <27000000>;
> @@ -1306,7 +1306,7 @@ dsi0_phy: dsi-phy@...0200 {
>                         reg-names = "dsi_pll", "dsi_phy", "dsi_phy_regulator";
>                         clock-names = "iface_clk", "ref";
>                         clocks = <&mmcc DSI_M_AHB_CLK>,
> -                                <&cxo_board>;
> +                                <&pxo_board>;
>                 };
>
>
> --
> 2.33.0
>


-- 
With best wishes
Dmitry