linux-kernel - RE: [PATCH v10 6/7] PCI: imx6: Mark the link down as none fatal error

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Date:   Tue, 14 Jun 2022 01:02:43 +0000
From:   Hongxing Zhu <hongxing.zhu@....com>
To:     Bjorn Helgaas <helgaas@...nel.org>
CC:     "l.stach@...gutronix.de" <l.stach@...gutronix.de>,
        "bhelgaas@...gle.com" <bhelgaas@...gle.com>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "broonie@...nel.org" <broonie@...nel.org>,
        "lorenzo.pieralisi@....com" <lorenzo.pieralisi@....com>,
        "festevam@...il.com" <festevam@...il.com>,
        "francesco.dolcini@...adex.com" <francesco.dolcini@...adex.com>,
        "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>,
        dl-linux-imx <linux-imx@....com>
Subject: RE: [PATCH v10 6/7] PCI: imx6: Mark the link down as none fatal error

> -----Original Message-----
> From: Bjorn Helgaas <helgaas@...nel.org>
> Sent: 2022年6月14日 6:21
> To: Hongxing Zhu <hongxing.zhu@....com>
> Cc: l.stach@...gutronix.de; bhelgaas@...gle.com; robh+dt@...nel.org;
> broonie@...nel.org; lorenzo.pieralisi@....com; festevam@...il.com;
> francesco.dolcini@...adex.com; linux-pci@...r.kernel.org;
> linux-arm-kernel@...ts.infradead.org; linux-kernel@...r.kernel.org;
> kernel@...gutronix.de; dl-linux-imx <linux-imx@....com>
> Subject: Re: [PATCH v10 6/7] PCI: imx6: Mark the link down as none fatal error
> 
> On Mon, Jun 13, 2022 at 04:55:37PM +0800, Richard Zhu wrote:
> > let the driver probe successfully, return zero in
> > imx6_pcie_start_link() when PCIe link is down.
> >
> > Because i.MX PCIe doesn't support hot-plug feature.
> > In this link down scenario, only start the PCIe link training in
> > resume when the link is up before system suspend to avoid the long
> > latency in the link training period.
> 
> This looks like two changes that should be separate patches:
> 
>   1) Make driver probe successful even if link is down.
> 
>   2) Reduce resume time by only starting the link if it was up before
>      suspend.
Yes, you're right.
They are two changes. Would split them into two patches later.
Thanks a lot for your kindly help.

Best Regards
Richard Zhu
> 
> > Signed-off-by: Richard Zhu <hongxing.zhu@....com>
> > ---
> >  drivers/pci/controller/dwc/pci-imx6.c | 18 +++++++++++-------
> >  1 file changed, 11 insertions(+), 7 deletions(-)
> >
> > diff --git a/drivers/pci/controller/dwc/pci-imx6.c
> > b/drivers/pci/controller/dwc/pci-imx6.c
> > index c02748393aac..ac6ec2d691a0 100644
> > --- a/drivers/pci/controller/dwc/pci-imx6.c
> > +++ b/drivers/pci/controller/dwc/pci-imx6.c
> > @@ -67,6 +67,7 @@ struct imx6_pcie {
> >  	struct dw_pcie		*pci;
> >  	int			reset_gpio;
> >  	bool			gpio_active_high;
> > +	bool			link_is_up;
> >  	struct clk		*pcie_bus;
> >  	struct clk		*pcie_phy;
> >  	struct clk		*pcie_inbound_axi;
> > @@ -845,7 +846,9 @@ static int imx6_pcie_start_link(struct dw_pcie *pci)
> >  	/* Start LTSSM. */
> >  	imx6_pcie_ltssm_enable(dev);
> >
> > -	dw_pcie_wait_for_link(pci);
> > +	ret = dw_pcie_wait_for_link(pci);
> > +	if (ret)
> > +		goto err_reset_phy;
> >
> >  	if (pci->link_gen == 2) {
> >  		/* Allow Gen2 mode after the link is up. */ @@ -881,11 +884,14
> @@
> > static int imx6_pcie_start_link(struct dw_pcie *pci)
> >  		}
> >
> >  		/* Make sure link training is finished as well! */
> > -		dw_pcie_wait_for_link(pci);
> > +		ret = dw_pcie_wait_for_link(pci);
> > +		if (ret)
> > +			goto err_reset_phy;
> >  	} else {
> >  		dev_info(dev, "Link: Gen2 disabled\n");
> >  	}
> >
> > +	imx6_pcie->link_is_up = true;
> >  	tmp = dw_pcie_readw_dbi(pci, offset + PCI_EXP_LNKSTA);
> >  	dev_info(dev, "Link up, Gen%i\n", tmp & PCI_EXP_LNKSTA_CLS);
> >  	return 0;
> > @@ -895,7 +901,7 @@ static int imx6_pcie_start_link(struct dw_pcie *pci)
> >  		dw_pcie_readl_dbi(pci, PCIE_PORT_DEBUG0),
> >  		dw_pcie_readl_dbi(pci, PCIE_PORT_DEBUG1));
> >  	imx6_pcie_reset_phy(imx6_pcie);
> > -	return ret;
> > +	return 0;
> >  }
> >
> >  static int imx6_pcie_host_init(struct pcie_port *pp) @@ -1022,10
> > +1028,8 @@ static int imx6_pcie_resume_noirq(struct device *dev)
> >  	imx6_pcie_init_phy(imx6_pcie);
> >  	imx6_pcie_deassert_core_reset(imx6_pcie);
> >  	dw_pcie_setup_rc(pp);
> > -
> > -	ret = imx6_pcie_start_link(imx6_pcie->pci);
> > -	if (ret < 0)
> > -		dev_info(dev, "pcie link is down after resume.\n");
> > +	if (imx6_pcie->link_is_up)
> > +		imx6_pcie_start_link(imx6_pcie->pci);
> >
> >  	return 0;
> >  }
> > --
> > 2.25.1
> >
> >
> > _______________________________________________
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