[PATCH v2] irqchip/imx-irqsteer: Allow building as module

From: Jindong Yue <[email protected]>

Make the driver buildable as a module by turning the Kconfig symbol into
a tristate and using module_platform_driver() instead of
builtin_platform_driver().

The existing remove() was incomplete for the module case, where the
driver can now be unloaded and reloaded. Fix it up:

 - dispose the parent IRQ mappings from irq_of_parse_and_map(), which
   were leaked on unload;
 - dispose the child mappings before irq_domain_remove(), otherwise the
   irq_descs keep pointing at imx_irqsteer_irq_chip in the freed module,
   which blows up on the next /proc/interrupts read;
 - resume the device before clk_disable_unprepare(), since it may be
   runtime suspended with the clock already off, and skip the disable if
   the resume fails;
 - disable runtime PM to balance the pm_runtime_enable() from probe().

Signed-off-by: Jindong Yue <[email protected]>
Signed-off-by: Zhipeng Wang <[email protected]>
---
Changes in v2 (addressing Sashiko AI review of v1):
 - remove(): dispose child and parent IRQ mappings before
   irq_domain_remove(), fixing a use-after-free of imx_irqsteer_irq_chip
   (in freed module memory) on the next /proc/interrupts read after
   unload;
 - remove(): disable runtime PM to balance the pm_runtime_enable() from
   probe(), so reload no longer warns about unbalanced runtime PM; resume
   the device first and skip clk_disable_unprepare() if the resume fails,
   keeping the ipg clock balanced.

v1: https://lore.kernel.org/r/[email protected]
 drivers/irqchip/Kconfig            |  2 +-
 drivers/irqchip/irq-imx-irqsteer.c | 26 +++++++++++++++++++++++---
 2 files changed, 24 insertions(+), 4 deletions(-)

diff --git a/drivers/irqchip/Kconfig b/drivers/irqchip/Kconfig
index 42f2278a702d..07db3b678f94 100644
--- a/drivers/irqchip/Kconfig
+++ b/drivers/irqchip/Kconfig
@@ -560,7 +560,7 @@ config CSKY_APB_INTC
 	  the controller's register.
 
 config IMX_IRQSTEER
-	bool "i.MX IRQSTEER support"
+	tristate "i.MX IRQSTEER support"
 	depends on ARCH_MXC || ARCH_S32 || COMPILE_TEST
 	default y if ARCH_MXC || ARCH_S32
 	select IRQ_DOMAIN
diff --git a/drivers/irqchip/irq-imx-irqsteer.c b/drivers/irqchip/irq-imx-irqsteer.c
index 87b07f517be3..da3889036182 100644
--- a/drivers/irqchip/irq-imx-irqsteer.c
+++ b/drivers/irqchip/irq-imx-irqsteer.c
@@ -10,6 +10,7 @@
 #include <linux/irqchip/chained_irq.h>
 #include <linux/irqdomain.h>
 #include <linux/kernel.h>
+#include <linux/module.h>
 #include <linux/of.h>
 #include <linux/of_irq.h>
 #include <linux/platform_device.h>
@@ -274,7 +275,7 @@ static int imx_irqsteer_probe(struct platform_device *pdev)
 static void imx_irqsteer_remove(struct platform_device *pdev)
 {
 	struct irqsteer_data *irqsteer_data = platform_get_drvdata(pdev);
-	int i;
+	int hwirq, i, ret;
 
 	for (i = 0; i < irqsteer_data->irq_count; i++) {
 		if (!irqsteer_data->irq[i])
@@ -282,11 +283,26 @@ static void imx_irqsteer_remove(struct platform_device *pdev)
 
 		irq_set_chained_handler_and_data(irqsteer_data->irq[i],
 						 NULL, NULL);
+		irq_dispose_mapping(irqsteer_data->irq[i]);
 	}
 
+	for (hwirq = 0; hwirq < irqsteer_data->reg_num * 32; hwirq++)
+		irq_dispose_mapping(irq_find_mapping(irqsteer_data->domain,
+						     hwirq));
+
 	irq_domain_remove(irqsteer_data->domain);
 
-	clk_disable_unprepare(irqsteer_data->ipg_clk);
+	/*
+	 * Device may be runtime suspended, with the ipg clock already gated.
+	 * Resume it so the clock is balanced by the disable below; if resume
+	 * fails the clock stays gated, so skip the disable in that case.
+	 */
+	ret = pm_runtime_get_sync(&pdev->dev);
+	pm_runtime_disable(&pdev->dev);
+	pm_runtime_put_noidle(&pdev->dev);
+
+	if (ret >= 0)
+		clk_disable_unprepare(irqsteer_data->ipg_clk);
 }
 
 #ifdef CONFIG_PM
@@ -349,6 +365,7 @@ static const struct of_device_id imx_irqsteer_dt_ids[] = {
 	{ .compatible = "nxp,s32n79-irqsteer",	.data = &s32n79_data },
 	{},
 };
+MODULE_DEVICE_TABLE(of, imx_irqsteer_dt_ids);
 
 static struct platform_driver imx_irqsteer_driver = {
 	.driver = {
@@ -359,4 +376,7 @@ static struct platform_driver imx_irqsteer_driver = {
 	.probe		= imx_irqsteer_probe,
 	.remove		= imx_irqsteer_remove,
 };
-builtin_platform_driver(imx_irqsteer_driver);
+module_platform_driver(imx_irqsteer_driver);
+
+MODULE_DESCRIPTION("i.MX IRQSTEER interrupt multiplexer/remapper driver");
+MODULE_LICENSE("GPL");
-- 
2.34.1