Latency in GPIO interrupts

Question

I am trying to implement an interrupt routine with an incoming interrupt every 25us(microseconds). Basically on each interrupt, I will set another gpio, output gpio, high for around 25us and reset the gpio to low after. I measured the input from the interrupt gpio and the output gpio. I realised that my callback/interrupt routine only executes about every 500us. I would like to know there is a way to increase the reaction to interrupt.

I am using the SBC ccimx6ul pro with the Digi yocto os.

Answer 1

We have done some interrupt latency performance measurements (1) for Cortex A8 (note the i.MX6UL has cortex A7 though) with the following numbers:

No preempt: 293us
Preempt: 88us
Preempt RT: 55us
Those are coherent with the GPIO-API measurements on the CC6UL on non-preempted kernels, so I'd say that around 50us for fully preemptible kernels is the theoretical maximum.

(1)https://events.static.linuxfound.org/sites/events/files/slides/toyooka_LCJ2014_v10.pdf