[PATCH v4 4/4] PCI: j721e: Add support to build as a loadable module

[Siddharth Vadapalli <s-vadapalli@ti.com>]

The 'pci-j721e.c' driver is the application/glue/wrapper driver for the
Cadence PCIe Controllers on TI SoCs. Implement support for building it as a
loadable module.

Signed-off-by: Siddharth Vadapalli <s-vadapalli@ti.com>
---

v3 patch is at:
https://lore.kernel.org/r/20250410104426.463453-5-s-vadapalli@ti.com/
Changes since v3:
- In the fourth patch of this series, the polarity for PERST# assert in
  the driver's .remove callback has been fixed based on Mani's feedback at
  https://lore.kernel.org/r/6bi5gul3sqvycmkf6cwokkvownjffaf2tkonjlefo2d7cautwx@uhfexzgz3okp/

Regards,
Siddharth.

 drivers/pci/controller/cadence/Kconfig     |  6 ++---
 drivers/pci/controller/cadence/pci-j721e.c | 31 +++++++++++++++++++++-
 2 files changed, 33 insertions(+), 4 deletions(-)

diff --git a/drivers/pci/controller/cadence/Kconfig b/drivers/pci/controller/cadence/Kconfig
index 82b58096eea0..72d7d264d6c3 100644
--- a/drivers/pci/controller/cadence/Kconfig
+++ b/drivers/pci/controller/cadence/Kconfig
@@ -43,10 +43,10 @@ config PCIE_CADENCE_PLAT_EP
 	  different vendors SoCs.
 
 config PCI_J721E
-	bool
+	tristate
 
 config PCI_J721E_HOST
-	bool "TI J721E PCIe controller (host mode)"
+	tristate "TI J721E PCIe controller (host mode)"
 	depends on ARCH_K3 || COMPILE_TEST
 	depends on OF
 	select PCIE_CADENCE_HOST
@@ -57,7 +57,7 @@ config PCI_J721E_HOST
 	  core.
 
 config PCI_J721E_EP
-	bool "TI J721E PCIe controller (endpoint mode)"
+	tristate "TI J721E PCIe controller (endpoint mode)"
 	depends on ARCH_K3 || COMPILE_TEST
 	depends on OF
 	depends on PCI_ENDPOINT
diff --git a/drivers/pci/controller/cadence/pci-j721e.c b/drivers/pci/controller/cadence/pci-j721e.c
index ef1cfdae33bb..8a73a4d382d1 100644
--- a/drivers/pci/controller/cadence/pci-j721e.c
+++ b/drivers/pci/controller/cadence/pci-j721e.c
@@ -15,6 +15,7 @@
 #include <linux/irqchip/chained_irq.h>
 #include <linux/irqdomain.h>
 #include <linux/mfd/syscon.h>
+#include <linux/module.h>
 #include <linux/of.h>
 #include <linux/pci.h>
 #include <linux/platform_device.h>
@@ -27,6 +28,7 @@
 #define cdns_pcie_to_rc(p) container_of(p, struct cdns_pcie_rc, pcie)
 
 #define ENABLE_REG_SYS_2	0x108
+#define ENABLE_CLR_REG_SYS_2	0x308
 #define STATUS_REG_SYS_2	0x508
 #define STATUS_CLR_REG_SYS_2	0x708
 #define LINK_DOWN		BIT(1)
@@ -116,6 +118,15 @@ static irqreturn_t j721e_pcie_link_irq_handler(int irq, void *priv)
 	return IRQ_HANDLED;
 }
 
+static void j721e_pcie_disable_link_irq(struct j721e_pcie *pcie)
+{
+	u32 reg;
+
+	reg = j721e_pcie_intd_readl(pcie, ENABLE_CLR_REG_SYS_2);
+	reg |= pcie->linkdown_irq_regfield;
+	j721e_pcie_intd_writel(pcie, ENABLE_CLR_REG_SYS_2, reg);
+}
+
 static void j721e_pcie_config_link_irq(struct j721e_pcie *pcie)
 {
 	u32 reg;
@@ -633,9 +644,23 @@ static void j721e_pcie_remove(struct platform_device *pdev)
 	struct j721e_pcie *pcie = platform_get_drvdata(pdev);
 	struct cdns_pcie *cdns_pcie = pcie->cdns_pcie;
 	struct device *dev = &pdev->dev;
+	struct cdns_pcie_ep *ep;
+	struct cdns_pcie_rc *rc;
+
+	if (pcie->mode == PCI_MODE_RC) {
+		rc = container_of(cdns_pcie, struct cdns_pcie_rc, pcie);
+		cdns_pcie_host_disable(rc);
+	} else {
+		ep = container_of(cdns_pcie, struct cdns_pcie_ep, pcie);
+		cdns_pcie_ep_disable(ep);
+	}
+
+	if (pcie->reset_gpio)
+		gpiod_set_value_cansleep(pcie->reset_gpio, 0);
 
 	clk_disable_unprepare(pcie->refclk);
 	cdns_pcie_disable_phy(cdns_pcie);
+	j721e_pcie_disable_link_irq(pcie);
 	pm_runtime_put(dev);
 	pm_runtime_disable(dev);
 }
@@ -730,4 +755,8 @@ static struct platform_driver j721e_pcie_driver = {
 		.pm	= pm_sleep_ptr(&j721e_pcie_pm_ops),
 	},
 };
-builtin_platform_driver(j721e_pcie_driver);
+module_platform_driver(j721e_pcie_driver);
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("PCIe controller driver for TI's J721E and related SoCs");
+MODULE_AUTHOR("Kishon Vijay Abraham I <kishon@ti.com>");
-- 
2.34.1