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

[Hongxing Zhu]

> -----Original Message-----
> From: Bjorn Helgaas <helgaas at kernel.org>
> Sent: 2025年9月25日 4:00
> To: Hongxing Zhu <hongxing.zhu at nxp.com>
> Cc: Frank Li <frank.li at nxp.com>; jingoohan1 at gmail.com;
> l.stach at pengutronix.de; lpieralisi at kernel.org; kwilczynski at kernel.org;
> mani at kernel.org; robh at kernel.org; bhelgaas at google.com;
> shawnguo at kernel.org; s.hauer at pengutronix.de; kernel at pengutronix.de;
> festevam at gmail.com; linux-pci at vger.kernel.org;
> linux-arm-kernel at lists.infradead.org; imx at lists.linux.dev;
> linux-kernel at vger.kernel.org; stable at vger.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 at 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 at nxp.com>
> > Reviewed-by: Frank Li <Frank.Li at 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?
Up to now, it is used to fix the issue encountered by i.MX7D PCIe.
If the LTSSM stat is changed, for example one device is new inserted if Hot-Plug
 is supported. The procedure of PME_Turn_Off kick off would terminated by the
 hot-plug event I think.

Best Regards
Richard Zhu
> 
> > +		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
> >
> >