Re: [PATCH V2 2/4] dt-bindings: imx6q-pcie: Add wake-gpios property

[Francesco Dolcini <francesco@dolcini.it>]

On Mon, Apr 07, 2025 at 07:18:32AM +0000, Sherry Sun wrote:
> 
> 
> > -----Original Message-----
> > From: Francesco Dolcini <francesco@dolcini.it>
> > Sent: Friday, April 4, 2025 5:42 PM
> > To: Sherry Sun <sherry.sun@nxp.com>
> > Cc: Hongxing Zhu <hongxing.zhu@nxp.com>; l.stach@pengutronix.de;
> > lpieralisi@kernel.org; kw@linux.com; robh@kernel.org;
> > bhelgaas@google.com; krzysztof.kozlowski+dt@linaro.org;
> > conor+dt@kernel.org; shawnguo@kernel.org; s.hauer@pengutronix.de;
> > kernel@pengutronix.de; festevam@gmail.com; dl-linux-imx <linux-
> > imx@nxp.com>; linux-pci@vger.kernel.org; linux-arm-
> > kernel@lists.infradead.org; devicetree@vger.kernel.org; linux-
> > kernel@vger.kernel.org
> > Subject: Re: [PATCH V2 2/4] dt-bindings: imx6q-pcie: Add wake-gpios property
> > 
> > Hello
> > 
> > On Wed, Dec 13, 2023 at 05:28:48PM +0800, Sherry Sun wrote:
> > > Add wake-gpios property that can be used to wakeup the host processor.
> > >
> > > Signed-off-by: Sherry Sun <sherry.sun@nxp.com>
> > > Reviewed-by: Richard Zhu <hongxing.zhu@nxp.com>
> > > ---
> > >  Documentation/devicetree/bindings/pci/fsl,imx6q-pcie.yaml | 6 ++++++
> > >  1 file changed, 6 insertions(+)
> > >
> > > diff --git a/Documentation/devicetree/bindings/pci/fsl,imx6q-pcie.yaml
> > > b/Documentation/devicetree/bindings/pci/fsl,imx6q-pcie.yaml
> > > index 81bbb8728f0f..fba757d937e1 100644
> > > --- a/Documentation/devicetree/bindings/pci/fsl,imx6q-pcie.yaml
> > > +++ b/Documentation/devicetree/bindings/pci/fsl,imx6q-pcie.yaml
> > > @@ -72,6 +72,12 @@ properties:
> > >        L=operation state) (optional required).
> > >      type: boolean
> > >
> > > +  wake-gpios:
> > > +    description: If present this property specifies WAKE# sideband signaling
> > > +      to implement wakeup functionality. This is an input GPIO pin for the
> > Root
> > > +      Port mode here. Host drivers will wakeup the host using the IRQ
> > > +      corresponding to the passed GPIO.
> > > +
> > 
> > From what I know it is possible to share the same WAKE# signal for multiple
> > root ports. Is this going to work fine with this binding? Same question on the
> > driver.
> > 
> > We do have design exactly like that, so it's not a theoretical question.
> > 
> The current design doesn't support such case, maybe some changes in the
> driver could achieve that (mark the wake-gpio as GPIOD_FLAGS_BIT_NONEXCLUSIVE
> and the interrupt as IRQF_SHARED, etc.).

Can you consider implementing this?

> But usually each RC has its own WAKE# pin assigned. We have not come across a
> case where multiple RC share the same WAKE# pin.

We do have such design, with an NXP iMX95 SoC, available now.

Francesco