linux-kernel - Re: [PATCH v4 5/5] phy: qcom: qmp-pcie: add x1e80100 qref supplies

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Message-ID: <296a9ab8-04e3-4623-8246-c8fd3fca8d98@oss.qualcomm.com>
Date: Sat, 14 Jun 2025 21:59:13 +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,
        vkoul@...nel.org, kishon@...nel.org, sfr@...b.auug.org.au,
        linux-phy@...ts.infradead.org, krishna.chundru@....qualcomm.com,
        quic_vbadigan@...cinc.com, quic_mrana@...cinc.com,
        quic_cang@...cinc.com, qiang.yu@....qualcomm.com,
        Johan Hovold <johan+linaro@...nel.org>,
        Abel Vesa <abel.vesa@...aro.org>
Subject: Re: [PATCH v4 5/5] phy: qcom: qmp-pcie: add x1e80100 qref supplies

On 6/4/25 5:10 PM, Johan Hovold wrote:
> On Wed, Jun 04, 2025 at 04:02:37PM +0800, Wenbin Yao wrote:
>> From: Qiang Yu <qiang.yu@....qualcomm.com>
>>
>> All PCIe PHYs on the X1E80100 SOC require the vdda-qref, which feeds QREF
>> clocks provided by the TCSR device.
> 
> As I just mentioned in the thread where this is still being discussed:
> 
> 	https://lore.kernel.org/all/aEBfV2M-ZqDF7aRz@hovoldconsulting.com
> 
> you need to provide a lot more detail on why you think modelling these
> supplies as PHY supplies (which they are not) is the right thing to do.
> 
> Also please answer the question I've asked three times now on how the
> QREF supplies map to PHY supplies on X1E as no one will be able to use
> this binding unless this is documented somewhere (and similar for other
> SoCs).
> 
> The fact that you so far have not been able to provide an answer
> seems to suggest that these supplies need to be managed by the TCSR
> clock driver which can handle the mapping.

To emphasize, we apparently can't do it, because there exist IPs
where the QREF *ref clock* is not expressed through a bit in TCSR
(which we interpret as TCSR_CC), but the *supply* for that clock must
still be described somehow, as it obviously needs power.

To add to the mess, it may be that there is more than one supply
per reference clock required (which is not necessarily an issue
when the driver takes care of it, but something to keep in mind).

Konrad