RE: [PATCH V2] arm64: dts: imx8mp-evk: Disable PCIe bus in the default dts

[Sherry Sun]

> On Tue, Mar 24, 2026 at 02:45:39AM +0000, Sherry Sun wrote:
> > > > Subject: Re: [PATCH V2] arm64: dts: imx8mp-evk: Disable PCIe bus
> > > > in the default dts
> > > >
> > > > On Fri, Mar 20, 2026 at 05:03:53PM +0800, Sherry Sun wrote:
> > > > > Disable the PCIe bus in the default device tree to avoid shared
> > > > > regulator conflicts between SDIO and PCIe buses. The
> > > > > non-deterministic probe order between these two buses can break
> > > > > the PCIe initialization sequence, causing PCIe devices to fail
> > > > > detection
> > > intermittently.
> > > > >
> > > > > On i.MX8MP EVK board, the M.2 connector is physically wired to
> > > > > both
> > > > > USDHC1 and PCIe0, however the out-of-box module is SDIO IW612
> > > > > WiFi, so enable the SDIO WiFi in the default imx8mp-evk.dts, and
> > > > > provide a separate device tree overlay (imx8mp-evk-pcie.dtso) to
> > > > > enable the PCIe bus when needed.
> > > > >
> > > > > Signed-off-by: Sherry Sun <sherry.sun@xxxxxxx>
> > > > > ---
> > > > > Chanegs in V2:
> > > > > 1. Improve the commit message to clarify SDIO WiFi is the
> > > > > out-of-box
> > > > module on
> > > > >    i.MX8MP EVK board.
> > > > > ---
> > > > >  arch/arm64/boot/dts/freescale/Makefile        |  4 +++-
> > > > >  .../boot/dts/freescale/imx8mp-evk-pcie.dtso   | 19
> > > +++++++++++++++++++
> > > > >  arch/arm64/boot/dts/freescale/imx8mp-evk.dts  |  4 ++--
> > > > >  3 files changed, 24 insertions(+), 3 deletions(-)  create mode
> > > > > 100644 arch/arm64/boot/dts/freescale/imx8mp-evk-pcie.dtso
> > > > >
> > > > > diff --git a/arch/arm64/boot/dts/freescale/Makefile
> > > > > b/arch/arm64/boot/dts/freescale/Makefile
> > > > > index 780682258e71..107ca270ef32 100644
> > > > > --- a/arch/arm64/boot/dts/freescale/Makefile
> > > > > +++ b/arch/arm64/boot/dts/freescale/Makefile
> > > > > @@ -333,12 +333,14 @@ imx8mp-evk-lvds0-imx-lvds-hdmi-dtbs +=
> > > > > imx8mp-evk.dtb imx8mp-evk-lvds0-imx-lvds-
> > > > > imx8mp-evk-lvds1-imx-dlvds-hdmi-channel0-dtbs += imx8mp-evk.dtb
> > > > > imx8mp-evk-lvds1-imx-dlvds-hdmi-channel0.dtbo
> > > > >  imx8mp-evk-lvds1-imx-lvds-hdmi-dtbs += imx8mp-evk.dtb
> > > > > imx8mp-evk-lvds1-imx-lvds-hdmi.dtbo
> > > > >  imx8mp-evk-mx8-dlvds-lcd1-dtbs += imx8mp-evk.dtb
> > > > > imx8mp-evk-mx8-dlvds-lcd1.dtbo -imx8mp-evk-pcie-ep-dtbs +=
> > > > > imx8mp-evk.dtb imx-pcie0-ep.dtbo
> > > > > +imx8mp-evk-pcie-dtbs := imx8mp-evk.dtb imx8mp-evk-pcie.dtbo
> > > > > +imx8mp-evk-pcie-ep-dtbs += imx8mp-evk-pcie.dtb
> > > > > +imx-pcie0-ep.dtbo
> > > > >  dtb-$(CONFIG_ARCH_MXC) +=
> > > > > imx8mp-evk-lvds0-imx-dlvds-hdmi-channel0.dtb
> > > > >  dtb-$(CONFIG_ARCH_MXC) += imx8mp-evk-lvds0-imx-lvds-hdmi.dtb
> > > > >  dtb-$(CONFIG_ARCH_MXC) +=
> > > > > imx8mp-evk-lvds1-imx-dlvds-hdmi-channel0.dtb
> > > > >  dtb-$(CONFIG_ARCH_MXC) += imx8mp-evk-lvds1-imx-lvds-hdmi.dtb
> > > > >  dtb-$(CONFIG_ARCH_MXC) += imx8mp-evk-mx8-dlvds-lcd1.dtb
> > > > > +dtb-$(CONFIG_ARCH_MXC) += imx8mp-evk-pcie.dtb
> > > > >  dtb-$(CONFIG_ARCH_MXC) += imx8mp-evk-pcie-ep.dtb
> > > > >
> > > > >  imx8mp-tqma8mpql-mba8mpxl-lvds-tm070jvhg33-dtbs +=
> > > > > imx8mp-tqma8mpql-mba8mpxl.dtb
> > > > > imx8mp-tqma8mpql-mba8mpxl-lvds-tm070jvhg33.dtbo
> > > > > diff --git a/arch/arm64/boot/dts/freescale/imx8mp-evk-pcie.dtso
> > > > > b/arch/arm64/boot/dts/freescale/imx8mp-evk-pcie.dtso
> > > > > new file mode 100644
> > > > > index 000000000000..4f6546d442bf
> > > > > --- /dev/null
> > > > > +++ b/arch/arm64/boot/dts/freescale/imx8mp-evk-pcie.dtso
> > > > > @@ -0,0 +1,19 @@
> > > > > +// SPDX-License-Identifier: (GPL-2.0+ OR MIT)
> > > > > +/*
> > > > > + * Copyright 2026 NXP
> > > > > + */
> > > > > +
> > > > > +/dts-v1/;
> > > > > +/plugin/;
> > > > > +
> > > > > +&pcie_phy {
> > > > > +	status = "okay";
> > > > > +};
> > > > > +
> > > > > +&pcie0 {
> > > > > +	status = "okay";
> > > > > +};
> > > > > +
> > > > > +&usdhc1 {
> > > > > +	status = "disabled";
> > > > > +};
> > > >
> > > > Please use one overlay for both imx95 and imx8mp to enable pcie0
> > > > and disable usdhc1.
> > >
> > > Hi Frank,
> > >
> > > imx8mp has a specific pcie_phy, I disabled it in the default
> > > imx8mp-evk.dts
> 
> Suppose, you needn't disable phy.
> 
> > > and enabled it in xxx-pcie.dtso, if we use one overlay for both
> > > imx95 and imx8mp, is it acceptable that we need to keep the 8mp
> > > pcie_phy enabled even in non-PCIe usage scenarios?
> > >
> >
> > In addition, another difference between imx8mp and imx95 is that imx8mp
> connects usdhc1 to the M.2 connector, while imx95 connects usdhc3 to the
> M.2 connector. The usdhc interfaces are different, so we cannot use the same
> DTSO file.
> 
> you use addtional label.
> 
> for example
> 
> m2_usdhc: &usdhc1 {
> 	...
> };
> 
> in overlay file
> 
> &m2_usdhc {
> 	status = "disabled";
> }
> 

Ok, thanks for the suggestion, will try this in next version.

Best Regards
Sherry