Re: [PATCH 1/2] dt-bindings: phy: qcom,sc8280xp-qmp-pcie-phy: Add vdda-refgen supply for Glymur

From: Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>
To: Qiang Yu <qiang.yu@oss.qualcomm.com>,
	Krzysztof Kozlowski <krzk@kernel.org>
Cc: Vinod Koul <vkoul@kernel.org>,
	Neil Armstrong <neil.armstrong@linaro.org>,
	Rob Herring <robh@kernel.org>,
	Krzysztof Kozlowski <krzk+dt@kernel.org>,
	Conor Dooley <conor+dt@kernel.org>,
	linux-arm-msm@vger.kernel.org, linux-phy@lists.infradead.org,
	devicetree@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/2] dt-bindings: phy: qcom,sc8280xp-qmp-pcie-phy: Add vdda-refgen supply for Glymur
Date: Thu, 12 Feb 2026 10:23:57 +0100	[thread overview]
Message-ID: <d7c66964-48b3-49ed-8d52-5341c382c1ca@oss.qualcomm.com> (raw)
In-Reply-To: <aY1Jx5J8x/OALk5M@hu-qianyu-lv.qualcomm.com>

On 2/12/26 4:32 AM, Qiang Yu wrote:
> On Mon, Feb 09, 2026 at 09:06:23AM +0100, Krzysztof Kozlowski wrote:
>> On Sun, Feb 08, 2026 at 08:49:39PM -0800, Qiang Yu wrote:
>>> The PCIe QMP PHYs on Glymur require stable reference voltage provided by
>>> refgen. The refgen itself requires two separate power supplies:
>>> vdda-refgen0p9 and vdda-refgen1p2.
>>>
>>> Since there is no dedicated driver for REFGEN, add vdda-refgen0p9-supply
>>
>> How does the driver matter for the bindings? If I add dedicated driver
>> for refgen, then I change the bindings?
> 
> Yeah, I know that dt-bindings should describe hardware, not software. But
> what I meant to say is that the refgen is different from qref which is
> controlled via TCSR registers and its LDOs are requested to vote in
> tcsrcc driver. The refgen doesn't required register setting and it doesn't
> have dedicated driver, so we vote its LDOs in phy driver. I will avoid
> this statement in next version.
> 
>>
>> There is qcom,sc8280xp-refgen-regulator so why there cannot be
>> qcom,x1e-refgen-regulator?
> 
> I think we can and it seems better because the refgen for pcie phy also
> supplies reference voltage to other modules like usb. But I checked the
> qcom-refgen-regulator.c, it contains some register settings and there is
> no LDOs voting. I'm not sure what does those register do, maybe Konrad
> can provide some backgroud. But on Glymur, we only need to vote LDOs. So
> what if we use a fixed regulator in the device tree to represent refgen?
> We could set refgen0p9 and refgen1p2 as its input supplies, then the PCIe
> PHY would just need one refgen supply reference.

That refgen on e.g. 8280 supplies display and camera PHYs. The latter have
some sideband interface to request a vote directly (on all but some single
old SoCs, IIUC), while the display ones need a manual vote.

It would stand to reason that perhaps this MMIO-controlled regulator would
have some sort of a voltage input.. so maybe that's the missing part in the
story? I'm trying to find some answers but it's not easy..

Konrad

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