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

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Message-ID: <aAt54vikoREWZyGY@hovoldconsulting.com>
Date: Fri, 25 Apr 2025 14:02:42 +0200
From: Johan Hovold <johan@...nel.org>
To: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
Cc: Wenbin Yao <quic_wenbyao@...cinc.com>, 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 Fri, Apr 25, 2025 at 12:03:06PM +0200, Konrad Dybcio wrote:
> 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.

Then it sounds like the qref supplies should be marked as always-on. Can
they be disabled at all?

Johan