linux-kernel - Re: [PATCH v4 1/2] arm64: dts: qcom: qcs8300: add display dt nodes for MDSS, DPU, DisplayPort and eDP PHY

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Message-ID: <mj6hqitpp5nsmixo7udhbe7pbcr4qctbebhyvqtmamevq7zm5s@q7tpzaggabhn>
Date: Tue, 5 Aug 2025 08:15:29 +0300
From: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
To: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
Cc: Yongxing Mou <quic_yongmou@...cinc.com>,
        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>, linux-arm-msm@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 1/2] arm64: dts: qcom: qcs8300: add display dt nodes
 for MDSS, DPU, DisplayPort and eDP PHY

On Mon, Aug 04, 2025 at 02:34:56PM +0200, Konrad Dybcio wrote:
> On 8/4/25 6:39 AM, Yongxing Mou wrote:
> > 
> > 
> > On 2025/7/30 18:25, Konrad Dybcio wrote:
> >> On 7/30/25 11:49 AM, Yongxing Mou wrote:
> >>> Add devicetree changes to enable MDSS display-subsystem,
> >>> display-controller(DPU), DisplayPort controller and eDP PHY for
> >>> Qualcomm QCS8300 platform.
> >>>
> >>> Signed-off-by: Yongxing Mou <quic_yongmou@...cinc.com>
> >>> ---
> >>
> >> [...]
> >>
> >>> +
> >>> +                assigned-clocks = <&dispcc MDSS_DISP_CC_MDSS_VSYNC_CLK>;
> >>> +                assigned-clock-rates = <19200000>;
> >>
> >> is this necessary?
> >>
> > Emm, i try to remove assigned-clocks and assigned-clock-rates here, device can still work.. here we just want to keep consistent with sa8775p.
> 
> Dmitry, do you remember whether this is some relic of the past that
> was required at one point?

I think it was necessary for old platforms (MSM8916, MSM8939, MSM8953,
APQ8084, MSM8974, MSM8992/94, MSM8996, MSM8998, SDM630/660), which can
source vsync_clk_src either from the XO or from the GPLL / MMPLL.

> 
> The driver lists 19.2 as the only possible frequency for the source
> of this branch

-- 
With best wishes
Dmitry