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

[Bjorn Helgaas <helgaas@kernel.org>]

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@vger.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@nxp.com>
> Reviewed-by: Frank Li <Frank.Li@nxp.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
> 
>