linux-kernel - Re: [PATCH 1/3] arm64: dts: qcom: sc8280xp: Fix PCIe PHY power-domains

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Date: Fri, 29 Dec 2023 14:20:15 +0100
From: Johan Hovold <johan@...nel.org>
To: Konrad Dybcio <konrad.dybcio@...aro.org>
Cc: Bjorn Andersson <andersson@...nel.org>,
	Rob Herring <robh+dt@...nel.org>,
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Johan Hovold <johan+linaro@...nel.org>,
	Marijn Suijten <marijn.suijten@...ainline.org>,
	linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
	Konrad Dybcio <konrad.dybcio@...ainline.org>
Subject: Re: [PATCH 1/3] arm64: dts: qcom: sc8280xp: Fix PCIe PHY
 power-domains

On Fri, Dec 29, 2023 at 02:08:25PM +0100, Konrad Dybcio wrote:
> On 29.12.2023 12:24, Johan Hovold wrote:
> > On Wed, Dec 27, 2023 at 11:28:26PM +0100, Konrad Dybcio wrote:
> >> The PCIe GDSCs are only related to the RCs. The PCIe PHYs on the other
> >> hand, are powered by VDD_MX and their specific VDDA_PHY/PLL regulators.
> > 
> > No, that does not seem to be entirely correct. I added the power-domains
> > here precisely because they were needed to enable the PHYs.

> > If you try to enable one of these PHYs without the corresponding GDSC
> > being enabled, you end up with:
> > 
> > [   37.709324] ------------[ cut here ]------------
> > [   37.718196] gcc_pcie_3b_aux_clk status stuck at 'off'
> > [   37.718205] WARNING: CPU: 4 PID: 482 at drivers/clk/qcom/clk-branch.c:86 clk_branch_wait+0x144/0x15c
> > 	
> > Now, you may or may not want to describe the above in the devicetree,
> > but this makes it sound like you're trying to work around an issue with
> > the current Linux implementation.

> Could you please recheck this with patch 1 from [1] applied?

As expected that makes no difference as I'm powering on the PHY without
the corresponding controller being enabled (which otherwise guarantees
the GDSC to be on).

> [1] https://lore.kernel.org/linux-arm-msm/20231227-topic-8280_pcie-v1-1-095491baf9e4@linaro.org/T/#u

Johan