linux-kernel - Re: [PATCH v6 3/4] PCI: dwc: Skip PME_Turn_Off message if there is no endpoint connected

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Message-ID: <20250924195955.GA2132329@bhelgaas>
Date: Wed, 24 Sep 2025 14:59:55 -0500
From: Bjorn Helgaas <helgaas@...nel.org>
To: Richard Zhu <hongxing.zhu@....com>
Cc: frank.li@....com, jingoohan1@...il.com, l.stach@...gutronix.de,
	lpieralisi@...nel.org, kwilczynski@...nel.org, mani@...nel.org,
	robh@...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,
	imx@...ts.linux.dev, linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Subject: Re: [PATCH v6 3/4] PCI: dwc: Skip PME_Turn_Off message if there is
 no endpoint connected

On Wed, Sep 24, 2025 at 03:23:23PM +0800, Richard Zhu wrote:
> A chip freeze is observed on i.MX7D when PCIe RC kicks off the PM_PME
> message and no any devices are connected on the port.

s/no any/no/

> To workaroud such kind of issue, skip PME_Turn_Off message if there is
> no endpoint connected.

s/workaroud/work around/

> Cc: stable@...r.kernel.org
> Fixes: 4774faf854f5 ("PCI: dwc: Implement generic suspend/resume functionality")
> Fixes: a528d1a72597 ("PCI: imx6: Use DWC common suspend resume method")
> Signed-off-by: Richard Zhu <hongxing.zhu@....com>
> Reviewed-by: Frank Li <Frank.Li@....com>
> ---
>  drivers/pci/controller/dwc/pcie-designware-host.c | 15 +++++++++------
>  1 file changed, 9 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/pci/controller/dwc/pcie-designware-host.c b/drivers/pci/controller/dwc/pcie-designware-host.c
> index 57a1ba08c427..b303a74b0fd7 100644
> --- a/drivers/pci/controller/dwc/pcie-designware-host.c
> +++ b/drivers/pci/controller/dwc/pcie-designware-host.c
> @@ -1008,12 +1008,15 @@ int dw_pcie_suspend_noirq(struct dw_pcie *pci)
>  	u32 val;
>  	int ret;
>  
> -	if (pci->pp.ops->pme_turn_off) {
> -		pci->pp.ops->pme_turn_off(&pci->pp);
> -	} else {
> -		ret = dw_pcie_pme_turn_off(pci);
> -		if (ret)
> -			return ret;
> +	/* Skip PME_Turn_Off message if there is no endpoint connected */
> +	if (dw_pcie_get_ltssm(pci) > DW_PCIE_LTSSM_DETECT_WAIT) {

This looks racy and it sounds like this is a workaround for an i.MX7D
defect.  Should it be some kind of quirk just for i.MX7D?

> +		if (pci->pp.ops->pme_turn_off) {
> +			pci->pp.ops->pme_turn_off(&pci->pp);
> +		} else {
> +			ret = dw_pcie_pme_turn_off(pci);
> +			if (ret)
> +				return ret;
> +		}
>  	}
>  
>  	if (dwc_quirk(pci, QUIRK_NOL2POLL_IN_PM)) {
> -- 
> 2.37.1
> 
>