Re: [PATCH v7 2/4] PCI: imx6: Allow probe deferal by reset GPIO

[Lucas Stach]

Am Dienstag, den 21.03.2017, 06:42 -0700 schrieb Andrey Smirnov:
> Some designs implement reset GPIO via a GPIO expander connected to a
> peripheral bus. One such example would be i.MX7 Sabre board where said
> GPIO is provided by SPI shift register connected to a bitbanged SPI
> bus. In order to support such designs allow reset GPIO request to defer
> probing of the driver.
> 
> Cc: yurovsky@xxxxxxxxx
> Cc: Lucas Stach <l.stach@xxxxxxxxxxxxxx>
> Cc: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
> Cc: Fabio Estevam <fabio.estevam@xxxxxxx>
> Cc: Dong Aisheng <dongas86@xxxxxxxxx>
> Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
> Cc: linux-kernel@xxxxxxxxxxxxxxx
> Signed-off-by: Andrey Smirnov <andrew.smirnov@xxxxxxxxx>

Reviewed-by: Lucas Stach <l.stach@xxxxxxxxxxxxxx>

> ---
>  drivers/pci/dwc/pci-imx6.c | 25 +++++++++++++++++--------
>  1 file changed, 17 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/pci/dwc/pci-imx6.c b/drivers/pci/dwc/pci-imx6.c
> index e0c36d6..64de9bb 100644
> --- a/drivers/pci/dwc/pci-imx6.c
> +++ b/drivers/pci/dwc/pci-imx6.c
> @@ -595,8 +595,8 @@ static struct dw_pcie_host_ops imx6_pcie_host_ops = {
>  	.host_init = imx6_pcie_host_init,
>  };
>  
> -static int __init imx6_add_pcie_port(struct imx6_pcie *imx6_pcie,
> -				     struct platform_device *pdev)
> +static int imx6_add_pcie_port(struct imx6_pcie *imx6_pcie,
> +			      struct platform_device *pdev)
>  {
>  	struct dw_pcie *pci = imx6_pcie->pci;
>  	struct pcie_port *pp = &pci->pp;
> @@ -636,7 +636,7 @@ static const struct dw_pcie_ops dw_pcie_ops = {
>  	.link_up = imx6_pcie_link_up,
>  };
>  
> -static int __init imx6_pcie_probe(struct platform_device *pdev)
> +static int imx6_pcie_probe(struct platform_device *pdev)
>  {
>  	struct device *dev = &pdev->dev;
>  	struct dw_pcie *pci;
> @@ -660,10 +660,6 @@ static int __init imx6_pcie_probe(struct platform_device *pdev)
>  	imx6_pcie->variant =
>  		(enum imx6_pcie_variants)of_device_get_match_data(dev);
>  
> -	/* Added for PCI abort handling */
> -	hook_fault_code(16 + 6, imx6q_pcie_abort_handler, SIGBUS, 0,
> -		"imprecise external abort");
> -
>  	dbi_base = platform_get_resource(pdev, IORESOURCE_MEM, 0);
>  	pci->dbi_base = devm_ioremap_resource(dev, dbi_base);
>  	if (IS_ERR(pci->dbi_base))
> @@ -683,6 +679,8 @@ static int __init imx6_pcie_probe(struct platform_device *pdev)
>  			dev_err(dev, "unable to get reset gpio\n");
>  			return ret;
>  		}
> +	} else if (imx6_pcie->reset_gpio == -EPROBE_DEFER) {
> +		return imx6_pcie->reset_gpio;
>  	}
>  
>  	/* Fetch clocks */
> @@ -796,11 +794,22 @@ static struct platform_driver imx6_pcie_driver = {
>  		.name	= "imx6q-pcie",
>  		.of_match_table = imx6_pcie_of_match,
>  	},
> +	.probe    = imx6_pcie_probe,
>  	.shutdown = imx6_pcie_shutdown,
>  };
>  
>  static int __init imx6_pcie_init(void)
>  {
> -	return platform_driver_probe(&imx6_pcie_driver, imx6_pcie_probe);
> +	/*
> +	 * Since probe() can be deferred we need to make sure that
> +	 * hook_fault_code is not called after __init memory is freed
> +	 * by kernel and since imx6q_pcie_abort_handler() is a no-op
> +	 * we can install the handler here without risking it
> +	 * accessing some unitialized driver state
> +	 */
> +	hook_fault_code(16 + 6, imx6q_pcie_abort_handler, SIGBUS, 0,
> +			"imprecise external abort");
> +
> +	return platform_driver_register(&imx6_pcie_driver);
>  }
>  device_initcall(imx6_pcie_init);