linux-kernel - Re: [PATCH v4 2/2] PCI: imx6: Enable the vaux regulator when fetch it

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Message-ID: <kvvluy56sdg6khv33cowseog4ujuebxzotlxm3hvm35slbenc5@rf3wttsd2niz>
Date: Tue, 19 Aug 2025 14:22:09 +0530
From: Manivannan Sadhasivam <mani@...nel.org>
To: Richard Zhu <hongxing.zhu@....com>
Cc: frank.li@....com, l.stach@...gutronix.de, lpieralisi@...nel.org, 
	kwilczynski@...nel.org, robh@...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 v4 2/2] PCI: imx6: Enable the vaux regulator when fetch it

On Tue, Aug 19, 2025 at 03:16:30PM GMT, Richard Zhu wrote:
> Enable the vaux regulator at probe time and keep it enabled for the
> entire PCIe controller lifecycle. This ensures support for outbound
> wake-up mechanism such as WAKE# signaling.
> 
> Signed-off-by: Richard Zhu <hongxing.zhu@....com>
> ---
>  drivers/pci/controller/dwc/pci-imx6.c | 15 +++++++++++++++
>  1 file changed, 15 insertions(+)
> 
> diff --git a/drivers/pci/controller/dwc/pci-imx6.c b/drivers/pci/controller/dwc/pci-imx6.c
> index 5a38cfaf989b1..1c1dce2d87e44 100644
> --- a/drivers/pci/controller/dwc/pci-imx6.c
> +++ b/drivers/pci/controller/dwc/pci-imx6.c
> @@ -159,6 +159,7 @@ struct imx_pcie {
>  	u32			tx_deemph_gen2_6db;
>  	u32			tx_swing_full;
>  	u32			tx_swing_low;
> +	struct regulator	*vaux;
>  	struct regulator	*vpcie;
>  	struct regulator	*vph;
>  	void __iomem		*phy_base;
> @@ -1739,6 +1740,20 @@ static int imx_pcie_probe(struct platform_device *pdev)
>  	pci->max_link_speed = 1;
>  	of_property_read_u32(node, "fsl,max-link-speed", &pci->max_link_speed);
>  
> +	/*
> +	 * 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, get the vaux and keep it
> +	 * enabled to power up WAKE# circuit for the entire PCIe controller
> +	 * lifecycle when WAKE# is supported.
> +	 */

This comment implies that the presence of Vaux is dependent on WAKE#. But there
is no such check present in the code. Maybe you are referring to the fact that
the platform will only supply Vaux if it intends to support WAKE#?

But I guess you can just drop the comment altogether and move it to patch
description.

- Mani

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