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

Shawn Guo
2025-11-12T01:51:37Z

On Tue, Nov 11, 2025 at 11:10:05AM -0500, Frank Li wrote:
> On Tue, Nov 11, 2025 at 08:02:35AM +0000, Hongxing Zhu wrote:
> > > -----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
>
> Shawn:
>
> This file should be removed. It is already merge to Rob's dt-scheme
> as PCIe standard properties.
>
> See: https://github.com/devicetree-org/dt-schema/blob/main/dtschema/schemas/pci/pci-bus-common.yaml

Ah, thanks!

Rob,

So it's no longer the case that kernel Documentation/devicetree/bindings
has all bindings documentation? Or it's never been the case? I used to
grep a property in the folder to see if it's documented or not.

Shawn