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

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Message-ID: <20241107072005.GA378841@rocinante>
Date: Thu, 7 Nov 2024 16:20:05 +0900
From: Krzysztof Wilczyński <kw@...ux.com>
To: Hongxing Zhu <hongxing.zhu@....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

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.

Thank you!

	Krzysztof