RE: [PATCH v6 01/11] arm64: dts: imx95-15x15-evk: Add supports-clkreq property to PCIe M.2 port

Hongxing Zhu
2025-11-11T08:02:39Z

> -----Original Message-----
> From: Shawn Guo <shawnguo2@yeah.net>
> Sent: 2025年11月11日 15:11
> To: Hongxing Zhu <hongxing.zhu@nxp.com>
> Cc: Frank Li <frank.li@nxp.com>; l.stach@pengutronix.de;
> lpieralisi@kernel.org; kwilczynski@kernel.org; mani@kernel.org;
> robh@kernel.org; krzk+dt@kernel.org; conor+dt@kernel.org;
> bhelgaas@google.com; shawnguo@kernel.org; s.hauer@pengutronix.de;
> kernel@pengutronix.de; festevam@gmail.com; linux-pci@vger.kernel.org;
> linux-arm-kernel@lists.infradead.org; devicetree@vger.kernel.org;
> imx@lists.linux.dev; linux-kernel@vger.kernel.org
> Subject: Re: [PATCH v6 01/11] arm64: dts: imx95-15x15-evk: Add
> supports-clkreq property to PCIe M.2 port
>
> On Wed, Oct 15, 2025 at 11:04:18AM +0800, Richard Zhu wrote:
> > According to PCIe r6.1, sec 5.5.1.
> >
> > The following rules define how the L1.1 and L1.2 substates are entered:
> > Both the Upstream and Downstream Ports must monitor the logical state
> > of the CLKREQ# signal.
> >
> > Typical implement is using open drain, which connect RC's clkreq# to
> > EP's clkreq# together and pull up clkreq#.
> >
> > imx95-15x15-evk matches this requirement, so add supports-clkreq to
> > allow PCIe device enter ASPM L1 Sub-State.
> >
> > Signed-off-by: Richard Zhu <hongxing.zhu@nxp.com>
> > ---
> > arch/arm64/boot/dts/freescale/imx95-15x15-evk.dts | 1 +
> > 1 file changed, 1 insertion(+)
> >
> > diff --git a/arch/arm64/boot/dts/freescale/imx95-15x15-evk.dts
> > b/arch/arm64/boot/dts/freescale/imx95-15x15-evk.dts
> > index 148243470dd4a..3ee032c154fa3 100644
> > --- a/arch/arm64/boot/dts/freescale/imx95-15x15-evk.dts
> > +++ b/arch/arm64/boot/dts/freescale/imx95-15x15-evk.dts
> > @@ -556,6 +556,7 @@ &pcie0 {
> > pinctrl-names = "default";
> > reset-gpio = <&gpio5 13 GPIO_ACTIVE_LOW>;
> > vpcie-supply = <&reg_m2_pwr>;
> > + supports-clkreq;
>
> Is binding updated for this property?
>
> Shawn
>
Hi Shawn:
As I know that It's a documented binding property as below.
- supports-clkreq:
If present this property specifies that CLKREQ signal routing exists from
root port to downstream device and host bridge drivers can do programming
which depends on CLKREQ signal existence. For example, programming root port
not to advertise ASPM L1 Sub-States support if there is no CLKREQ signal.
./Documentation/devicetree/bindings/pci/pci.txt

Best Regards
Richard Zhu

> > status = "okay";
> > };
> >
> > --
> > 2.37.1
> >