Re: [PATCH V3] PCI: rcar: Add the initialization of PCIe link in resume_noirq()

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On Thu, Mar 28, 2019 at 09:18:22AM -0500, Bjorn Helgaas wrote:
> On Mon, Mar 25, 2019 at 08:43:19PM +0100, marek.vasut@xxxxxxxxx wrote:
> > From: Kazufumi Ikeda <kaz-ikeda@xxxxxxxxxxxxx>
> > 
> > Reestablish the PCIe link very early in the resume process in case it
> > went down to prevent PCI accesses from hanging the bus. Such accesses
> > can happen early in the PCI resume process, as early as the
> > SUSPEND_RESUME_NOIRQ step, thus the link must be reestablished in the
> > driver resume_noirq() callback.
> > 
> > Fixes: e015f88c368d ("PCI: rcar: Add support for R-Car H3 to pcie-rcar")
> 
> I'm fine with the fix itself, but since e015f88c368d appeared more
> than two years ago in v4.5, the justification for merging this after
> the merge window is a little weak.
> 
> Is there a more recent change that exposed this problem?  The usual
> situation is that we merged something during the v5.1 merge window
> that caused a regression, and we're now fixing that before v5.1 final.

I do not think that's urgent enough to merge it in one of the -rc* but I
won't speak for the authors - it will trickle back anyway through the
stable mechanism, I just queued it as a fix since that's how it
qualifies.

So postponing it to v5.2 is fine by me, just let me know how it is best
to handle it.

Thanks,
Lorenzo

> Bjorn
> 
> > Signed-off-by: Kazufumi Ikeda <kaz-ikeda@xxxxxxxxxxxxx>
> > Signed-off-by: Gaku Inami <gaku.inami.xw@xxxxxxxxxxxxxx>
> > Signed-off-by: Marek Vasut <marek.vasut+renesas@xxxxxxxxx>
> > [lorenzo.pieralisi@xxxxxxx: reformatted commit log]
> > Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@xxxxxxx>
> > Reviewed-by: Simon Horman <horms+renesas@xxxxxxxxxxxx>
> > Acked-by: Wolfram Sang <wsa+renesas@xxxxxxxxxxxxxxxxxxxx>
> > Cc: stable@xxxxxxxxxxxxxxx
> > Cc: Geert Uytterhoeven <geert+renesas@xxxxxxxxx>
> > Cc: Phil Edworthy <phil.edworthy@xxxxxxxxxxx>
> > Cc: Simon Horman <horms+renesas@xxxxxxxxxxxx>
> > Cc: Wolfram Sang <wsa@xxxxxxxxxxxxx>
> > Cc: linux-renesas-soc@xxxxxxxxxxxxxxx
> > ---
> > V2: - Use BIT() macro for (1 << n)
> >     - Since polling in rcar_pcie_wait_for_dl() uses udelay(), do not
> >       add extra changes to this function anymore
> >     - Make resume_noirq return early and clean up parenthesis therein
> > V3: - Add missing PMSR register definition, dropped due to patch reshuffling
> > ---
> >  drivers/pci/controller/pcie-rcar.c | 21 +++++++++++++++++++++
> >  1 file changed, 21 insertions(+)
> > 
> > diff --git a/drivers/pci/controller/pcie-rcar.c b/drivers/pci/controller/pcie-rcar.c
> > index c8febb009454..6a4e435bd35f 100644
> > --- a/drivers/pci/controller/pcie-rcar.c
> > +++ b/drivers/pci/controller/pcie-rcar.c
> > @@ -46,6 +46,7 @@
> >  
> >  /* Transfer control */
> >  #define PCIETCTLR		0x02000
> > +#define  DL_DOWN		BIT(3)
> >  #define  CFINIT			1
> >  #define PCIETSTR		0x02004
> >  #define  DATA_LINK_ACTIVE	1
> > @@ -94,6 +95,7 @@
> >  #define MACCTLR			0x011058
> >  #define  SPEED_CHANGE		BIT(24)
> >  #define  SCRAMBLE_DISABLE	BIT(27)
> > +#define PMSR			0x01105c
> >  #define MACS2R			0x011078
> >  #define MACCGSPSETR		0x011084
> >  #define  SPCNGRSN		BIT(31)
> > @@ -1130,6 +1132,7 @@ static int rcar_pcie_probe(struct platform_device *pdev)
> >  	pcie = pci_host_bridge_priv(bridge);
> >  
> >  	pcie->dev = dev;
> > +	platform_set_drvdata(pdev, pcie);
> >  
> >  	err = pci_parse_request_of_pci_ranges(dev, &pcie->resources, NULL);
> >  	if (err)
> > @@ -1221,10 +1224,28 @@ static int rcar_pcie_probe(struct platform_device *pdev)
> >  	return err;
> >  }
> >  
> > +static int rcar_pcie_resume_noirq(struct device *dev)
> > +{
> > +	struct rcar_pcie *pcie = dev_get_drvdata(dev);
> > +
> > +	if (rcar_pci_read_reg(pcie, PMSR) &&
> > +	    !(rcar_pci_read_reg(pcie, PCIETCTLR) & DL_DOWN))
> > +		return 0;
> > +
> > +	/* Re-establish the PCIe link */
> > +	rcar_pci_write_reg(pcie, CFINIT, PCIETCTLR);
> > +	return rcar_pcie_wait_for_dl(pcie);
> > +}
> > +
> > +static const struct dev_pm_ops rcar_pcie_pm_ops = {
> > +	.resume_noirq = rcar_pcie_resume_noirq,
> > +};
> > +
> >  static struct platform_driver rcar_pcie_driver = {
> >  	.driver = {
> >  		.name = "rcar-pcie",
> >  		.of_match_table = rcar_pcie_of_match,
> > +		.pm = &rcar_pcie_pm_ops,
> >  		.suppress_bind_attrs = true,
> >  	},
> >  	.probe = rcar_pcie_probe,
> > -- 
> > 2.20.1
> > 



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