linux-kernel - Re: [PATCH v2 4/4] arm64: dts: qcom: x1e80100-qcp: Add qref supply for PCIe PHYs

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Message-ID: <e82eda3b-b27f-4584-ad23-562ca4b22847@oss.qualcomm.com>
Date: Fri, 25 Apr 2025 12:03:06 +0200
From: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
To: Johan Hovold <johan@...nel.org>, Wenbin Yao <quic_wenbyao@...cinc.com>
Cc: catalin.marinas@....com, will@...nel.org,
        linux-arm-kernel@...ts.infradead.org, andersson@...nel.org,
        konradybcio@...nel.org, robh@...nel.org, krzk+dt@...nel.org,
        conor+dt@...nel.org, linux-arm-msm@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        krishna.chundru@....qualcomm.com, quic_vbadigan@...cinc.com,
        quic_mrana@...cinc.com, quic_cang@...cinc.com, quic_qianyu@...cinc.com
Subject: Re: [PATCH v2 4/4] arm64: dts: qcom: x1e80100-qcp: Add qref supply
 for PCIe PHYs

On 4/25/25 11:51 AM, Johan Hovold wrote:
> On Fri, Apr 25, 2025 at 05:29:55PM +0800, Wenbin Yao wrote:
>> From: Qiang Yu <quic_qianyu@...cinc.com>
>>
>> All PCIe PHYs on X1E80100 require vdda-qref power supplies, but this is
>> missing in the current PHY device tree node. The PCIe port can still
>> function because the regulator L3J, which vdda-qref consumes, is voted by
>> other components.
>>
>> Since the device tree should accurately describe the hardware, add the
>> vdda-qref power supply explicitly in all PCIe PHY device nodes.
> 
> AFAIU the PHYs do not use this qref supply directly so it does not
> belong in the PHY node (but possibly in the tcsr node that provides the
> refclk).
> 
> Since commit 031b46b4729b ("phy: qcom: qmp-pcie: drop bogus x1e80100
> qref supplies") it also won't have any effect for pcie4 and pcie6.

QREF is a separate hw block distributing the reference clocks across
certain on-SoC peripherals

If its power goes out, I don't think much of the platform would be
functional anyway, so it's redundant here..

It doesn't have its own single register region and it's frankly
one-shot-configured way before Linux starts up, so there should be
no need of describing it at all.

Konrad