On Fri, Aug 18, 2017 at 10:34:19AM -0400, Cliff Brake wrote:

After a suggestion of using a NMI and a bit of research, it seems
something like the following article is the probably a reasonable
approach:

http://free-electrons.com/blog/fiq-handlers-in-the-arm-linux-kernel/

The use of a FIQ probably gives you the best chance to achieve the
latencies you want; but keep in mind that the use of FIQ means you'll
need to get your hands pretty dirty.

The set of operations legal to perform from NMI context is very, very
small.  The usage of gpiolib (and therefore any existing i.MX gpio
driver) is probably not going to work from NMI context, so you'll have
to roll your own solution.

   Julia