// ========================================================================================================
// ========================================================================================================
// ************************************************* mult.c ***********************************************
// ========================================================================================================
// ========================================================================================================

#include <unistd.h>
#include <fcntl.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>  
#include <sys/mman.h>

#include <sys/types.h>
#include <sys/socket.h>
#include <arpa/inet.h> 
#include <netdb.h> 

#include <time.h>
#include <sys/time.h>

// =================================
// GPIO constants
#define GPIO_0_BASE_ADDR 0x41200000
#define CTRL_DIRECTION_MASK 0x00
#define DATA_DIRECTION_MASK 0xFFFFFFFF

#define OUT_CP_RESET 31


// ========================================================================================================
// ========================================================================================================
// ========================================================================================================

int main(int argc, char *argv[])
   {
   volatile unsigned int *CtrlRegA;
   volatile unsigned int *DataRegA;
   unsigned int ctrl_mask;

// ======================================================================================================================
// COMMAND LINE
   if ( argc != 1 )
      {
      printf("ERROR: GPIO.elf(): No Params)\n");
      return(1);
      }

// Open up the memory mapped device so we can access the GPIO registers.
   int fd = open("/dev/mem", O_RDWR|O_SYNC);

   if (fd < 0) 
      { printf("ERROR: /dev/mem could NOT be opened!\n"); exit(EXIT_FAILURE); }

// Add 2 for the DataReg (for an offset of 8 bytes for 32-bit integer variables)
   DataRegA = mmap(0, getpagesize(), PROT_READ|PROT_WRITE, MAP_SHARED, fd, GPIO_0_BASE_ADDR);
   CtrlRegA = DataRegA + 2;

// Set the control mask to 0.
   ctrl_mask = 0;
      
// Do a soft RESET
   *CtrlRegA = ctrl_mask | (1 << OUT_CP_RESET);
   *CtrlRegA = ctrl_mask;
   usleep(10000);

// Wait until multiplier is ready (should be ready immediately so this while should exit on the first iteration).
   while ( (*DataRegA & (1 << 31)) == 0 );

// Put 2 8-bit values to be multiplied in low order 16 bits of the ctrl_mask, and write them to CtrlReg
   ctrl_mask = 0x0000F285;
   *CtrlRegA = ctrl_mask;

// Start the multiplier and pass in the input operands.
   *CtrlRegA = ctrl_mask | (1 << 30);

// De-assert start immediately after asserting it to prevent state machine from continuously performing multiply operation.
   *CtrlRegA = ctrl_mask; 

// Wait for multiplier to finish.
   while ( (*DataRegA & (1 << 31)) == 0 );

// Print result -- mask off high order 16 bits, i.e., print only low order 16-bit result of multiply.
   printf("Result %04X\n", (*DataRegA & 0x0000FFFF)); fflush(stdout);

   return 0;
   }