[PATCH 3/3] genirq: Check for trigger type mismatch in __setup_irq()

[Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>]

Currently, if the trigger type defined by the platform like DT does not
match the driver requested trigger type, the below warning is shown
during platform_get_irq() but only during the second time of the drive
probe (due to probe deferral or module unload/load).

irq: type mismatch, failed to map hwirq-9 for interrupt-controller@b220000!

Consider a typical usecase of requesting an IRQ in a driver:

```
	/* Assume DT has set the trigger type to IRQF_TYPE_LEVEL_HIGH */

	q6v5->wdog_irq = platform_get_irq_byname(pdev, "wdog");
	if (q6v5->wdog_irq <= 0)
		return q6v5->wdog_irq;

	ret = devm_request_threaded_irq(&pdev->dev, q6v5->wdog_irq,
					NULL, q6v5_wdog_interrupt,
					IRQF_TRIGGER_RISING | IRQF_ONESHOT,
					"q6v5 wdog", q6v5);
	if (ret) {
		dev_err(&pdev->dev, "failed to acquire wdog IRQ\n");
		return ret;
	}
```

For the first time probe of a driver, platform_get_irq_byname() does not
return an error and it sets the platform requested trigger type. Then,
request_irq() also does not check for the trigger type mismatch and sets
the driver requested trigger type. Later if the driver gets probed again,
platform_get_irq() throws the "type mismatch" warning and fails.

Ideally, request_irq() should throw the error during the first time itself,
when it detects the trigger type mismatch. So let's add a check in
__setup_irq() for checking the trigger type mismatch.

It should be noted that the platform trigger type could be IRQ_TYPE_NONE
in some cases like IRQ controller inside the GPIOCHIP. For those cases,
the check should be skipped.

Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
---
 kernel/irq/manage.c | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
index c03f71d5ec10..dd28c4944172 100644
--- a/kernel/irq/manage.c
+++ b/kernel/irq/manage.c
@@ -1480,8 +1480,18 @@ __setup_irq(unsigned int irq, struct irq_desc *desc, struct irqaction *new)
 	 * If the trigger type is not specified by the caller,
 	 * then use the default for this interrupt.
 	 */
-	if (!(new->flags & IRQF_TRIGGER_MASK))
-		new->flags |= irqd_get_trigger_type(&desc->irq_data);
+	flags = irqd_get_trigger_type(&desc->irq_data);
+	if (!(new->flags & IRQF_TRIGGER_MASK)) {
+		new->flags |= flags;
+	} else if (flags && ((new->flags & IRQF_TRIGGER_MASK) != flags)) {
+		/*
+		 * Bail out if the default trigger is not IRQ_TYPE_NONE and the
+		 * caller specified trigger does not match the default trigger type.
+		 */
+		pr_err("Trigger type %u does not match default type %lu for %s (irq %d)\n",
+		       new->flags & IRQF_TRIGGER_MASK, flags, new->name, irq);
+		return -EINVAL;
+	}
 
 	/*
 	 * Check whether the interrupt nests into another interrupt
-- 
2.25.1