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

1 files changed, 17 insertions, 8 deletions

diff --git a/drivers/pci/dwc/pci-imx6.c b/drivers/pci/dwc/pci-imx6.c
index e0c36d6f5a21..d62ee3553cfe 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 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);