linux-kernel - RE: [PATCH v2] PCI: dwc: Fix resume failure if no EP is connected at some platforms

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Message-ID:
 <AS8PR04MB8676F00E8F76B695772EB3B18C5C2@AS8PR04MB8676.eurprd04.prod.outlook.com>
Date: Thu, 7 Nov 2024 08:40:56 +0000
From: Hongxing Zhu <hongxing.zhu@....com>
To: Krzysztof Wilczy��ski <kw@...ux.com>
CC: Bjorn Helgaas <helgaas@...nel.org>, "bhelgaas@...gle.com"
	<bhelgaas@...gle.com>, "lorenzo.pieralisi@....com"
	<lorenzo.pieralisi@....com>, Frank Li <frank.li@....com>, "mani@...nel.org"
	<mani@...nel.org>, "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org"
	<linux-arm-kernel@...ts.infradead.org>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, "kernel@...gutronix.de"
	<kernel@...gutronix.de>, "imx@...ts.linux.dev" <imx@...ts.linux.dev>
Subject: RE: [PATCH v2] PCI: dwc: Fix resume failure if no EP is connected at
 some platforms

> -----Original Message-----
> From: Krzysztof Wilczy��ski <kw@...ux.com>
> Sent: 2024年11月7日 15:20
> To: Hongxing Zhu <hongxing.zhu@....com>
> Cc: Bjorn Helgaas <helgaas@...nel.org>; bhelgaas@...gle.com;
> lorenzo.pieralisi@....com; Frank Li <frank.li@....com>; mani@...nel.org;
> linux-pci@...r.kernel.org; linux-arm-kernel@...ts.infradead.org;
> linux-kernel@...r.kernel.org; kernel@...gutronix.de; imx@...ts.linux.dev
> Subject: Re: [PATCH v2] PCI: dwc: Fix resume failure if no EP is connected at
> some platforms
> 
> Hello,
> 
> > > But I don't think you responded to the race question.  What happens
> here?
> > >
> > >   if (dw_pcie_get_ltssm(pci) > DW_PCIE_LTSSM_DETECT_ACT) {
> > >     --> link goes down here <--
> > >     pci->pp.ops->pme_turn_off(&pci->pp);
> > >
> > > You decide the LTSSM is active and the link is up.  Then the link goes
> down.
> > > Then you send PME_Turn_off.  Now what?
> > >
> > > If it's safe to try to send PME_Turn_off regardless of whether the
> > > link is up or down, there would be no need to test the LTSSM state.
> > I made a local tests on i.MX95/i.MX8QM/i.MX8MP/i.MX8MM/i.MX8MQ,
> and
> > confirm that it's safe to send PME_TURN_OFF although the link is down.
> > You're right. It's no need to test LTSSM state here.
> > So do the L2 poll listed above after PME_TURN_OFF is sent.
> >
> > Since the 6.13 merge window is almost closed.
> > How about I prepare another Fix patch to do the following items for
> > incoming 6.14?
> > - Before sending PME_TURN_OFF, don't test the LTSSM stat.
> > - Remove the L2 stat poll, after sending PME_TURN_OFF.
> 
> If the changes aren't too involved, then I would rather fix it or drop the not
> needed code now, before we sent the Pull Request.
> 
> So, feel free to sent a small patch against the current branch, or simply let me
> know how do you wish the current code to be changed, so I can do it against
> the current branch.
Thanks for your kindly reminder.
This clean up small patch is on the way.

Best Regards
Richard Zhu
> 
> Thank you!
> 
> 	Krzysztof