How to detect GPIO line interruption in Embedded Linux?

Question

An interrupt is generated every 10 ms on GPIO_39 in pandaboard OMAP4 . I registered a handler for this in the Linux driver code, but the handler is not called because no interrupt was detected.

I made sure at the hardware level (by checking the gpio pin) that the interrupt is actually generated. It is only that the software cannot detect it.

My driver code has the following.

#define GPIO_NO 39 iowrite16(0x3, gpio_39_address + 2); /* Configured the pin 22 to be used as gpio. */ ret = gpio_request(GPIO_NO, "Claiming GPIO"); if(ret < 0) { printk(KERN_ALERT "%s: Claiming GPIO_%d failed\n", __func__, GPIO_NO); return -1; } else { printk(KERN_INFO "%s: Claiming GPIO_%d successful\n", __func__, GPIO_NO); } ret = gpio_direction_input(GPIO_NO); if(ret < 0) { printk(KERN_INFO "%s: Setting GPIO direction to input failed\n", __func__); return -1; } else { printk(KERN_INFO "%s: Direction of GPIO_%d set to input\n", __func__, GPIO_NO); } GPIO_IRQ = gpio_to_irq(GPIO_NO); if(GPIO_IRQ < 0) { printk(KERN_INFO "%s: Mapping GPIO_%d to IRQ failed\n", __func__, GPIO_NO); return -1; } else { printk(KERN_INFO "%s: Mapping GPIO_%d to IRQ_%d successful\n", __func__, GPIO_NO, GPIO_IRQ); } if((request_irq(GPIO_IRQ, ten_ms_int, IRQF_TRIGGER_FALLING, DEVICE_NAME, NULL))) { printk(KERN_ALERT "%s: requeseting GPIO_IRQ %d failed\n", __func__, GPIO_IRQ); return -1; } else { printk(KERN_INFO "%s: requesting GPIO_IRQ %d successful\n", __func__, GPIO_IRQ); } irqreturn_t ten_ms_int(int irq, void *dev_id) { T_UINT32 l; /* Enable spi channel */ l = ioread32(spi_base + SPI_CHCONF0); l |= SPI_CHCONF0_FORCE; iowrite32(l, (spi_base + SPI_CHCONF0)); l = ioread32(spi_base + SPI_CHCTRL0); l |= SPI_CHCTRL_EN; iowrite32(l, (spi_base + SPI_CHCTRL0)); /* Enable dma channel 0 */ l = ioread32(sdma_base + SDMA_CCR(CHANNEL0)); l |= SDMA_CCR_ENABLE; iowrite32(l, sdma_base + SDMA_CCR(CHANNEL0)); /* Enable dma channel 1 */ l = ioread32(sdma_base + SDMA_CCR(CHANNEL1)); l |= SDMA_CCR_ENABLE; iowrite32(l, sdma_base + SDMA_CCR(CHANNEL1)); //printk(KERN_INFO "%s: 10ms interrupt detected %d\n", __func__, irq); /* I know that I've to remove this printk statement */ return IRQ_HANDLED; } 

GPIO_39 belongs to GPIO2, and the corresponding interrupt number is 32. But the return value of gpio_to_irq() is 199. This is another cause for concern.

Please let me know if something is wrong in the code or if I missed something.

Answer 1

Draw the GPIO output explicitly to detect a falling edge.

At the gpio module level, you must enable FALLING_DETECT gpio.