linux-kernel - Re: [PATCH v2 3/3] PCI: dwc: Check for the device presence during suspend and resume

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Message-ID: <aRISPgCZyEZxStIN@lizhi-Precision-Tower-5810>
Date: Mon, 10 Nov 2025 11:26:38 -0500
From: Frank Li <Frank.li@....com>
To: Manivannan Sadhasivam <manivannan.sadhasivam@....qualcomm.com>
Cc: lpieralisi@...nel.org, kwilczynski@...nel.org, mani@...nel.org,
	bhelgaas@...gle.com, will@...nel.org, linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org, robh@...nel.org,
	linux-arm-msm@...r.kernel.org, zhangsenchuan@...incomputing.com,
	vincent.guittot@...aro.org
Subject: Re: [PATCH v2 3/3] PCI: dwc: Check for the device presence during
 suspend and resume

On Fri, Nov 07, 2025 at 10:13:19AM +0530, Manivannan Sadhasivam wrote:
> If there is no device available under the Root Ports, there is no point in
> sending PME_Turn_Off and waiting for L2/L3 transition during suspend, it
> will result in a timeout. Hence, skip those steps if no device is available
> during suspend.
>
> During resume, do not wait for the link up if there was no device connected
> before suspend. It is very unlikely that a device will get connected while
> the host system was suspended.
>
> Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@....qualcomm.com>
> ---
>  drivers/pci/controller/dwc/pcie-designware-host.c | 13 +++++++++++++
>  1 file changed, 13 insertions(+)
>
> diff --git a/drivers/pci/controller/dwc/pcie-designware-host.c b/drivers/pci/controller/dwc/pcie-designware-host.c
> index 20c9333bcb1c..5a39e7139ec9 100644
> --- a/drivers/pci/controller/dwc/pcie-designware-host.c
> +++ b/drivers/pci/controller/dwc/pcie-designware-host.c
> @@ -20,6 +20,7 @@
>  #include <linux/platform_device.h>
>
>  #include "../../pci.h"
> +#include "../pci-host-common.h"
>  #include "pcie-designware.h"
>
>  static struct pci_ops dw_pcie_ops;
> @@ -1129,6 +1130,9 @@ int dw_pcie_suspend_noirq(struct dw_pcie *pci)
>  	u32 val;
>  	int ret;
>
> +	if (!pci_root_ports_have_device(pci->pp.bridge->bus))
> +		goto stop_link;
> +
>  	/*
>  	 * If L1SS is supported, then do not put the link into L2 as some
>  	 * devices such as NVMe expect low resume latency.
> @@ -1162,6 +1166,7 @@ int dw_pcie_suspend_noirq(struct dw_pcie *pci)
>  	 */
>  	udelay(1);

I think move pme_turn_off() to helper funciton will make code look better

	if (pci_root_ports_have_device()) {
		ret = dwc_pme_turn_off();
		if (ret)
			return ret;
	};


>
> +stop_link:
>  	dw_pcie_stop_link(pci);
>  	if (pci->pp.ops->deinit)
>  		pci->pp.ops->deinit(&pci->pp);
> @@ -1195,6 +1200,14 @@ int dw_pcie_resume_noirq(struct dw_pcie *pci)
>  	if (ret)
>  		return ret;
>
> +	/*
> +	 * If there was no device before suspend, skip waiting for link up as
> +	 * it is bound to fail. It is very unlikely that a device will get
> +	 * connected *during* suspend.

I think it should use certern term. the a device will not get linkup during
suspend, if this happen, it is a new hotjoin device after system resume.

Frank

> +	 */
> +	if (!pci_root_ports_have_device(pci->pp.bridge->bus))
> +		return 0;
> +
>  	ret = dw_pcie_wait_for_link(pci);
>  	if (ret)
>  		return ret;
> --
> 2.48.1
>