linux-kernel - Re: [PATCH] schemas: PCI: Add standard PCIe WAKE# signal

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Message-ID: <20250609143734.GA749760@bhelgaas>
Date: Mon, 9 Jun 2025 09:37:34 -0500
From: Bjorn Helgaas <helgaas@...nel.org>
To: Krishna Chaitanya Chundru <krishna.chundru@....qualcomm.com>
Cc: andersson@...nel.org, robh@...nel.org, dmitry.baryshkov@...aro.org,
	manivannan.sadhasivam@...aro.org, krzk@...nel.org,
	linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org,
	lpieralisi@...nel.org, kw@...ux.com, conor+dt@...nel.org,
	linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
	devicetree-spec@...r.kernel.org, quic_vbadigan@...cinc.com,
	sherry.sun@....com
Subject: Re: [PATCH] schemas: PCI: Add standard PCIe WAKE# signal

On Thu, May 15, 2025 at 02:35:17PM +0530, Krishna Chaitanya Chundru wrote:
> As per PCIe spec 6, sec 5.3.3.2 document PCI standard WAKE# signal,
> which is used to re-establish power and reference clocks to the
> components within its domain.
> 
> Signed-off-by: Krishna Chaitanya Chundru <krishna.chundru@....qualcomm.com>
> ---
>  dtschema/schemas/pci/pci-bus-common.yaml | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/dtschema/schemas/pci/pci-bus-common.yaml b/dtschema/schemas/pci/pci-bus-common.yaml
> index ca97a00..a39fafc 100644
> --- a/dtschema/schemas/pci/pci-bus-common.yaml
> +++ b/dtschema/schemas/pci/pci-bus-common.yaml
> @@ -142,6 +142,10 @@ properties:
>      description: GPIO controlled connection to PERST# signal
>      maxItems: 1
>  
> +  wake-gpios:
> +    description: GPIO controlled connection to WAKE# signal

"GPIO controlled" makes it sound like the GPIO can assert or deassert
the WAKE# signal.  But isn't WAKE# driven ("controlled") by a PCIe
endpoint, and this GPIO would be input-only at the other end to sense
the state of WAKE#?