CHIP Pro PIO Interrupt Debounce Register Clock select

debounce.c

/*

CHIP Pro PIO Interrupt Debounce Register Clock select
  https://github.com/NextThingCo/CHIP-Hardware/blob/master/CHIP%5Bv1_0%5D/CHIPv1_0-BOM-Datasheets/Allwinner%20R8%20User%20Manual%20V1.1.pdf
  Page 342

0: 32kHz
1: 24MHz

*/


#include <stdio.h>                                                                                                   
#include <stdlib.h>                                                                                                        
#include <sys/mman.h>                                                                                                            
#include <fcntl.h>                                                                                                                      
#include <unistd.h>                                                                                                                           
                                                                                                                                                   
                                                                                                                                                   
#define BASE 0x01C20800                                                                                                                              
#define CLOCKOFFSET 0x218                                                                                                                             
#define SIZE 0x20                                                                                                                                       
                                                                                                                                                           
int main(void){                                                                                                                                            
                                                                                                                                                           
        int fd = open("/dev/mem", O_RDWR|O_SYNC);                                                                                                             
        if (fd < 0){                                                                                                                                          
                fprintf(stderr, "Unable to open port\n\r");                                                                                                   
                exit(fd);                                                                                                                                      
        }                                                                                                                                                      
                                                                                                                                                               
        // Truncate offset to a multiple of the page size, or mmap will fail.
        size_t pagesize = sysconf(_SC_PAGE_SIZE);
        off_t page_base = (BASE / pagesize) * pagesize;
        off_t page_offset = BASE - page_base;

        printf("Pagesize: %d\n", sysconf(_SC_PAGE_SIZE));
        printf("Pagebase: %d\n", page_base);
        printf("Pageoffset: %d\n", page_offset);
        printf("clock addr: %d\n", page_base + page_offset + CLOCKOFFSET);


        volatile void * pio = mmap(NULL, page_offset + CLOCKOFFSET + SIZE, PROT_READ | PROT_WRITE, MAP_SHARED, fd, page_base);
        if (pio == MAP_FAILED){
                printf("rip\n");
                return -1;
        }

        volatile unsigned int * clock = pio + page_offset + CLOCKOFFSET;

        printf("Current clock is: %d\n",*clock); 
        *clock = 1;
        printf("And now is: %d\n",*clock); 

        munmap((void*)pio, page_offset + CLOCKOFFSET + SIZE);
        close(fd);

        return 0;
}