Hello List, I am on a raspberry pi zero, chipset BCM2835, and try to use the ARM timer to get FIQ interrupts. I compiled the kernel from source to be able to create my out-of-tree module. Uname -a gives: Linux raspberrypi 4.19.108+ #1 PREEMPT Tue Mar 31 10:00:18 CEST 2020 armv6l GNU/Linux (i only set it to be a low-latency-kernel) I try to create an fiq interrupt in a number of ways, but nothing works. The driver I created can be found at https://github.com/SietseAchterop/Batradio/blob/master/batradio_module/fiqte... The ARM timer is configured by directly writing to the registers. It is running fine and sets it's interrupt bit at some point. So I assume that linux does not use the ARM timer in a base configuration. When using: ret = claim_fiq(&bat_fh); set_fiq_handler(&batradio_handler, &batradio_handler_end - &batradio_handler); set_fiq_regs(®s); enable_fiq(x); There are no fiq interrupts, i tried several values of x. My main question is, which irq number should I use. Note that I use pdev = platform_device_register_simple("batradio__", 0, NULL, 0); to register this platform device. I did find a complete example in https://bootlin.com/blog/fiq-handlers-in-the-arm-linux-kernel/ But there they used a device tree and got the fiq-irq number via the probe function argument. Maybe that is a way to get it working, but I don't know with compatible value to use. I also tried, instead of enable_fiq, to directly connect the ARM timer to FIQ by writing 0xC0, 0x80 + 0x40, to the FIQ Control register 0x20C. But then Linux freezes immediately, so that's probably the wrong way. What could I do to get FIQ interrupts working? Or where can I find which irq number to use in enable_fiq? Hopefully someone can point me in a direction. Thanks in advance, Sietse PS. I forced dwc_otg to not use fiq by adding the following to /boot/cmdline.txt dwc_otg.fiq_fsm_enable=0 dwc_otg.fiq_enable=0 dwc_otg.nak_holdoff=0 I also make it boot up with console, so no X stuff, and access via ssh.