PCI: imx6: Allow probe deferral by reset GPIO

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.
To support such designs, allow reset GPIO request to defer probing of the
driver.

Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Lucas Stach <l.stach@pengutronix.de>
Cc: yurovsky@gmail.com
Cc: Fabio Estevam <fabio.estevam@nxp.com>
Cc: Dong Aisheng <dongas86@gmail.com>
Cc: linux-arm-kernel@lists.infradead.org
(cherry picked from commit bde4a5a00e761f55be92f62378cf5024ced79ee3)

diff --git a/drivers/pci/host/pci-imx6.c b/drivers/pci/host/pci-imx6.c
index bbd3a28..250952e 100644 (file)
--- a/drivers/pci/host/pci-imx6.c
+++ b/drivers/pci/host/pci-imx6.c
@@ -807,7 +807,7 @@ static struct 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,
+static int imx6_add_pcie_port(struct imx6_pcie *imx6_pcie,
                                     struct platform_device *pdev)
 {
        struct pcie_port *pp = &imx6_pcie->pp;
@@ -1181,7 +1181,7 @@ static const struct dev_pm_ops pci_imx_pm_ops = {
 };
 #endif
 
-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 imx6_pcie *imx6_pcie;
@@ -1208,10 +1208,6 @@ static int __init imx6_pcie_probe(struct platform_device *pdev)
                        return -EINVAL;
        }
 
-       /* Added for PCI abort handling */
-       hook_fault_code(16 + 6, imx6q_pcie_abort_handler, SIGBUS, 0,
-               "imprecise external abort");
-
 
        np = of_find_compatible_node(NULL, NULL, "fsl,imx-pcie-phy");
        if (np != NULL) {
@@ -1262,6 +1258,8 @@ 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 */
@@ -1572,11 +1570,22 @@ static struct platform_driver imx6_pcie_driver = {
                .of_match_table = imx6_pcie_of_match,
                .pm = &pci_imx_pm_ops,
        },
+       .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 uninitialized 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);