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

[Bjorn Helgaas <helgaas@kernel.org>]

On Mon, Mar 25, 2019 at 08:43:19PM +0100, marek.vasut@gmail.com wrote:
> From: Kazufumi Ikeda <kaz-ikeda@xc.jp.nec.com>
> 
> 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.

Bjorn

> Signed-off-by: Kazufumi Ikeda <kaz-ikeda@xc.jp.nec.com>
> Signed-off-by: Gaku Inami <gaku.inami.xw@bp.renesas.com>
> Signed-off-by: Marek Vasut <marek.vasut+renesas@gmail.com>
> [lorenzo.pieralisi@arm.com: reformatted commit log]
> Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
> Reviewed-by: Simon Horman <horms+renesas@verge.net.au>
> Acked-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
> Cc: stable@vger.kernel.org
> Cc: Geert Uytterhoeven <geert+renesas@glider.be>
> Cc: Phil Edworthy <phil.edworthy@renesas.com>
> Cc: Simon Horman <horms+renesas@verge.net.au>
> Cc: Wolfram Sang <wsa@the-dreams.de>
> Cc: linux-renesas-soc@vger.kernel.org
> ---
> 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
>