linux-kernel - Re: [PATCH 03/24] arm64: dts: qcom: Introduce Glymur base dtsi and CRD dts

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Message-ID: <gg7srymb2dspk4jeycc5su5gjl434ymgzapqqyqw7yq2marzue@ql27qx2ptuo6>
Date: Wed, 29 Oct 2025 12:36:43 +0200
From: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
To: Taniya Das <taniya.das@....qualcomm.com>
Cc: Konrad Dybcio <konrad.dybcio@....qualcomm.com>,
        Pankaj Patil <pankaj.patil@....qualcomm.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 03/24] arm64: dts: qcom: Introduce Glymur base dtsi and
 CRD dts

On Wed, Oct 29, 2025 at 03:30:54PM +0530, Taniya Das wrote:
> 
> 
> On 9/25/2025 3:46 PM, Konrad Dybcio wrote:
> >> +		tcsrcc: clock-controller@...5044 {
> >> +			compatible = "qcom,glymur-tcsr";
> >> +			reg = <0x0 0x1fd5044 0x0 0x48>;
> > We can map 0x1fd5000 - 0x1fd5094 inclusive, as that seems like a
> > logical subblock (this would require adjusting the driver)
> > 
> 
> Konrad, we encountered issues when trying to map regions beyond just the
> clock reference registers. Normally, we map the entire address range of
> a clock controller (CC) module in the device tree. However, for TCSRCC
> where CLKREF_EN registers are located within shared modules like TCSR or
> TLMM—we don't own the whole address space, and mapping the full range
> can overlap with other devices.
> To avoid this, we propose defining the base address as the first
> register actually used, and the size to only include up to the last
> register we use. This ensures we only map the relevant subblock,
> preventing conflicts with other device nodes.

Then you need to behave slightly differently: map the full range at the
basic device (TLMM, TCSR, etc.) and then create TCSRCC as a child device
to that node (and use paren't regmap to access the registers).

> 
> So want to keep the mapping same from the start of clockref clocks.
> 
> > There's also a laaaarge pool of various TCSR_ registers between
> > the previous node and this one.. but we can leave that in case we
> > need to describe it in a specific way some day
> >> +			#clock-cells = <1>;
> >> +			#reset-cells = <1>;
> >> +		};
> >> +
> 
> -- 
> Thanks,
> Taniya Das
> 

-- 
With best wishes
Dmitry