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

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Date: Fri, 29 Dec 2023 14:08:25 +0100
From: Konrad Dybcio <konrad.dybcio@...aro.org>
To: Johan Hovold <johan@...nel.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 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.
> 
> This is something I stumbled over when trying to figure out how to
> add support for the second lane pair (i.e. four-lane mode), and I just
> went back and confirmed that this is still the case.
> 
> 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?

Konrad

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