[PATCH v3 2/2] mfd: fsl-imx25: clean up irq settings during removal

[Martin Kaiser <martin@kaiser.cx>]

When fsl-imx25-tsadc is compiled as a module, loading, unloading and
reloading the module will lead to a crash.

Unable to handle kernel paging request at virtual address bf005430
[<c004df6c>] (irq_find_matching_fwspec)
   from [<c028d5ec>] (of_irq_get+0x58/0x74)
[<c028d594>] (of_irq_get)
   from [<c01ff970>] (platform_get_irq+0x48/0xc8)
[<c01ff928>] (platform_get_irq)
   from [<bf00e33c>] (mx25_tsadc_probe+0x220/0x2f4 [fsl_imx25_tsadc])

irq_find_matching_fwspec() loops over all registered irq domains. The
irq domain is still registered from last time the module was loaded but
the pointer to its operations is invalid after the module was unloaded.

Add a removal function which clears the irq handler and removes the irq
domain. With this cleanup in place, it's possible to unload and reload
the module.

Signed-off-by: Martin Kaiser <martin@kaiser.cx>
---
changes in v3:
 delete__exit qualifier from the remove routine

changes in v2:
 add more details about the crash to the commit message

 drivers/mfd/fsl-imx25-tsadc.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/drivers/mfd/fsl-imx25-tsadc.c b/drivers/mfd/fsl-imx25-tsadc.c
index 14189ef..dbb85ca 100644
--- a/drivers/mfd/fsl-imx25-tsadc.c
+++ b/drivers/mfd/fsl-imx25-tsadc.c
@@ -179,6 +179,19 @@ static int mx25_tsadc_probe(struct platform_device *pdev)
 	return devm_of_platform_populate(dev);
 }
 
+static int mx25_tsadc_remove(struct platform_device *pdev)
+{
+	struct mx25_tsadc *tsadc = platform_get_drvdata(pdev);
+	int irq = platform_get_irq(pdev, 0);
+
+	if (irq) {
+		irq_set_chained_handler_and_data(irq, NULL, NULL);
+		irq_domain_remove(tsadc->domain);
+	}
+
+	return 0;
+}
+
 static const struct of_device_id mx25_tsadc_ids[] = {
 	{ .compatible = "fsl,imx25-tsadc" },
 	{ /* Sentinel */ }
@@ -191,6 +204,7 @@ static struct platform_driver mx25_tsadc_driver = {
 		.of_match_table = of_match_ptr(mx25_tsadc_ids),
 	},
 	.probe = mx25_tsadc_probe,
+	.remove = mx25_tsadc_remove,
 };
 module_platform_driver(mx25_tsadc_driver);
 
-- 
2.1.4