[FAQ] TDA4VM: How to test GPIO interrupts

The interrupt path for GPIO on TDA4/J721e/J7200:

GPIO --> INTR(GPIO Interrupt Router) --> GIC500

Also note that in the Linux driver there is support for banked interrupts only & no support for unbanked interrupts.

We can validate the entire GPIO interrupt path mentioned above without even having to externally control
the GPIO pin. Here is a simple code snippet to configure a GPIO pin and register an interrupt handler.

Trick to generate/fake interrupt is to configure the GPIO as output & toggle the state of GPIO.
5635.0001-davinci_gpio-Test-interrupts.patch

Apply the above patch to Linux directory of PSDKLA 8.0

cd $PSDKLA_PATH/board-support/linux*

git am 0001-davinci_gpio-Test-interrupts.patch
cd ../..
make linux
Insert the SD card
Edit Rules.make to point DESTDIR to rootfs of SD card: DESTDIR=/media/$USER/rootfs

sudo make linux_install
sync

This should register a test interrupt handler for wkup_gpio module GPIO_52.

Once we boot up we need to figure out the GPIO numbering in Linux for wkup_gpio_52

cat /sys/class/gpio/gpiochip372/label
42110000.gpio

So the wkup_gpio module starts with 372 & hence wkup_gpio_52 will be 372+52 = 424

echo 424 > /sys/class/gpio/export
echo out > /sys/class/gpio/gpio424/direction
echo 1 > /sys/class/gpio/gpio424/value

One can see the print from wkup_gpio_52 test interrupt handler.

[   83.608230] test_irq: irq 293, val=0

We can also check the interrupt count increase:

cat /proc/interrupts | grep key-gpio
293: 2 0 GPIO 52 Edge -davinci_gpio key-gpio

Best Regards,
Keerthy