TS-7700 Interrupts
We include a userspace IRQ patch in our kernels. This allows you to receive interrupts from your applications where you would normally have to write a kernel driver. This works by creating a file for each interrupt in '/proc/irq/<irqnum>/irq'. The new irq file allows you to block on a read on the file until an interrupt fires.
The original patch is documented here.
The Linux kernel supports up to 16 IRQs from the FPGA. When the CPU receives an IRQ from the FPGA, it uses the IRQ register in the #Syscon to find out which IRQ on the MUX is triggering. Currently only three IRQs are used. Off-board IRQs 5, 6, and 7 correspond to FPGA IRQs 0, 1, and 2, respectively. FPGA IRQs 3 to 15 are reserved for future uses. If the DIO pins are not being used as IRQs, they can be masked out by writing 0 to the corresponding bit in the IRQ mask register.
IRQ # | Name |
---|---|
64 | XUART IRQ |
65 | CAN1 IRQ |
66 | Reserved |
70 | EVGPIO |
This example below will work with any of our products that support userspace IRQs. It opens the IRQ number specified in the first argument, and prints when it detects an IRQ.
#include <stdio.h>
#include <fcntl.h>
#include <sys/select.h>
#include <sys/stat.h>
#include <unistd.h>
int main(int argc, char **argv)
{
char proc_irq[32];
int ret, irqfd = 0;
int buf; // Holds irq junk data
fd_set fds;
if(argc < 2) {
printf("Usage: %s <irq number>\n", argv[0]);
return 1;
}
snprintf(proc_irq, sizeof(proc_irq), "/proc/irq/%d/irq", atoi(argv[1]));
irqfd = open(proc_irq, O_RDONLY| O_NONBLOCK, S_IREAD);
if(irqfd == -1) {
printf("Could not open IRQ %s\n", argv[1]);
return 1;
}
while(1) {
FD_SET(irqfd, &fds); //add the fd to the set
// See if the IRQ has any data available to read
ret = select(irqfd + 1, &fds, NULL, NULL, NULL);
if(FD_ISSET(irqfd, &fds))
{
FD_CLR(irqfd, &fds); //Remove the filedes from set
printf("IRQ detected\n");
// Clear the junk data in the IRQ file
read(irqfd, &buf, sizeof(buf));
}
//Sleep, or do any other processing here
usleep(10000);
}
return 0;
}