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

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Message-ID:
 <AS8PR04MB8676592EF1D6F2BDFA2348A18C532@AS8PR04MB8676.eurprd04.prod.outlook.com>
Date: Wed, 6 Nov 2024 02:06:09 +0000
From: Hongxing Zhu <hongxing.zhu@....com>
To: Bjorn Helgaas <helgaas@...nel.org>
CC: "kwilczynski@...nel.org" <kwilczynski@...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: Bjorn Helgaas <helgaas@...nel.org>
> Sent: 2024年11月6日 7:35
> To: Hongxing Zhu <hongxing.zhu@....com>
> Cc: kwilczynski@...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
> 
> On Mon, Jul 22, 2024 at 02:15:13PM +0800, Richard Zhu wrote:
> > The dw_pcie_suspend_noirq() function currently returns success
> > directly if no endpoint (EP) device is connected. However, on some
> > platforms, power loss occurs during suspend, causing dw_resume() to do
> nothing in this case.
> > This results in a system halt because the DWC controller is not
> > initialized after power-on during resume.
> >
> > Change call to deinit() in suspend and init() at resume regardless of
> > whether there are EP device connections or not. It is not harmful to
> > perform deinit() and init() again for the no power-off case, and it
> > keeps the code simple and consistent in logic.
> > ...
> 
> > -	ret = read_poll_timeout(dw_pcie_get_ltssm, val, val ==
> DW_PCIE_LTSSM_L2_IDLE,
> > -				PCIE_PME_TO_L2_TIMEOUT_US/10,
> > -				PCIE_PME_TO_L2_TIMEOUT_US, false, pci);
> > -	if (ret) {
> > -		dev_err(pci->dev, "Timeout waiting for L2 entry! LTSSM: 0x%x\n",
> val);
> > -		return ret;
> > +		ret = read_poll_timeout(dw_pcie_get_ltssm, val, val ==
> DW_PCIE_LTSSM_L2_IDLE,
> > +					PCIE_PME_TO_L2_TIMEOUT_US/10,
> > +					PCIE_PME_TO_L2_TIMEOUT_US, false, pci);
> > +		if (ret) {
> > +			dev_err(pci->dev, "Timeout waiting for L2 entry! LTSSM:
> 0x%x\n", val);
> > +			return ret;
> > +		}
> 
> Not related to this patch, but what's the reason for waiting for the link to
> enter L2?  There are a few other drivers that do this, but most don't.  Is
> there something else the driver needs to do after the link is in L2?
> 
Agree with you, I used to suggest Frank to remove the L2 polling too.

Best Regards
Richard Zhu
> >  	}
> >
> >  	if (pci->pp.ops->deinit)
> > --
> > 2.37.1
> >