linux-kernel - Re: [PATCH v5 3/4] arm64: dts: qcom: sa8775p: remove aux clock from pcie phy

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Message-ID: <86e14d55-8e96-4a2d-a9e8-a52f0de9dffd@oss.qualcomm.com>
Date: Fri, 18 Jul 2025 12:53:56 +0200
From: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
To: Johan Hovold <johan@...nel.org>,
        Ziyue Zhang <ziyue.zhang@....qualcomm.com>
Cc: andersson@...nel.org, konradybcio@...nel.org, robh@...nel.org,
        krzk+dt@...nel.org, conor+dt@...nel.org, jingoohan1@...il.com,
        mani@...nel.org, lpieralisi@...nel.org, kwilczynski@...nel.org,
        bhelgaas@...gle.com, johan+linaro@...nel.org, vkoul@...nel.org,
        kishon@...nel.org, neil.armstrong@...aro.org, abel.vesa@...aro.org,
        kw@...ux.com, linux-arm-msm@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-pci@...r.kernel.org, linux-phy@...ts.infradead.org,
        qiang.yu@....qualcomm.com, quic_krichai@...cinc.com,
        quic_vbadigan@...cinc.com
Subject: Re: [PATCH v5 3/4] arm64: dts: qcom: sa8775p: remove aux clock from
 pcie phy

On 7/18/25 12:02 PM, Johan Hovold wrote:
> On Fri, Jul 18, 2025 at 04:17:17PM +0800, Ziyue Zhang wrote:
>> gcc_aux_clk is used in PCIe RC and it is not required in pcie phy, in
>> pcie phy it should be gcc_phy_aux_clk, so remove gcc_aux_clk and
>> replace it with gcc_phy_aux_clk.
> 
> Expanding on why this is a correct change would be good since this does
> not yet seem to have been fully resolved:
> 
> 	https://lore.kernel.org/lkml/98088092-1987-41cc-ab70-c9a5d3fdbb41@oss.qualcomm.com/

I dug out some deep memories and recalled that _PHY_AUX_CLK was
necessary on x1e for the Gen4 PHY to initialize properly. This
can be easily reproduced:

diff --git a/arch/arm64/boot/dts/qcom/x1e80100.dtsi b/arch/arm64/boot/dts/qcom/x1e80100.dtsi
index a9a7bb676c6f..d5ef6bef2b23 100644
--- a/arch/arm64/boot/dts/qcom/x1e80100.dtsi
+++ b/arch/arm64/boot/dts/qcom/x1e80100.dtsi
@@ -3312,7 +3312,7 @@ pcie3_phy: phy@...0000 {
                        compatible = "qcom,x1e80100-qmp-gen4x8-pcie-phy";
                        reg = <0 0x01be0000 0 0x10000>;
 
-                       clocks = <&gcc GCC_PCIE_3_PHY_AUX_CLK>,
+                       clocks = <&gcc GCC_PCIE_3_AUX_CLK>,
                                 <&gcc GCC_PCIE_3_CFG_AHB_CLK>,
                                 <&tcsr TCSR_PCIE_8L_CLKREF_EN>,
                                 <&gcc GCC_PCIE_3_PHY_RCHNG_CLK>,

==>
[    6.967231] qcom-qmp-pcie-phy 1be0000.phy: phy initialization timed-out
[    6.974462] phy phy-1be0000.phy.0: phy poweron failed --> -110

And the (non-PHY_)AUX_CLK is necessary for at least one of them, as
removing it causes a crash on boot

Konrad