linux-kernel - Re: [PATCH v3 1/2] dt-bindings: PCI: fsl,imx6q-pcie: Add vaux for i.MX PCIe

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Message-ID: <20250820195944.GA596147-robh@kernel.org>
Date: Wed, 20 Aug 2025 14:59:44 -0500
From: Rob Herring <robh@...nel.org>
To: Frank Li <Frank.li@....com>
Cc: Richard Zhu <hongxing.zhu@....com>, l.stach@...gutronix.de,
	lpieralisi@...nel.org, kwilczynski@...nel.org, mani@...nel.org,
	krzk+dt@...nel.org, conor+dt@...nel.org, bhelgaas@...gle.com,
	shawnguo@...nel.org, s.hauer@...gutronix.de, kernel@...gutronix.de,
	festevam@...il.com, linux-pci@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, devicetree@...r.kernel.org,
	imx@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 1/2] dt-bindings: PCI: fsl,imx6q-pcie: Add vaux for
 i.MX PCIe

On Thu, Aug 14, 2025 at 03:02:18PM -0400, Frank Li wrote:
> On Thu, Aug 14, 2025 at 04:59:19PM +0800, Richard Zhu wrote:
> > Refer to PCIe CEM r6.0, sec 2.3 WAKE# Signal, WAKE# signal is only
> > asserted by the Add-in Card when all its functions are in D3Cold state
> > and at least one of its functions is enabled for wakeup generation.
> >
> > The 3.3V auxiliary power (+3.3Vaux) must be present and used for wakeup
> > process. Since the main power supply would be gated off to let Add-in
> > Card to be in D3Cold, add the vaux and keep it enabled to power up WAKE#
> > circuit for the entire PCIe controller lifecycle when WAKE# is supported.
> 
> if it is standard, it should move to snps,dw-pcie-common.yaml.

It is standard because PCIe spec defines them. pci-bus-common.yaml 
already defines these:

  vpcie12v-supply:
    description: 12v regulator phandle for the slot

  vpcie3v3-supply:
    description: 3.3v regulator phandle for the slot

  vpcie3v3aux-supply:
    description: 3.3v AUX regulator phandle for the slot

Note that these should really be defined in the root port node rather 
than the host bridge node. We've done the latter because the RP node is 
often not defined.

Rob