TB reading

gistfile1.c

#define TBU_USER 0x10C  /* Time Base Upper User for reading */ 
#define TBL_USER 0x10D  /* Time Base Lower User for reading */
#define TBU_SUPER 0x11C /* Time Base Upper Supervisor for writing */
#define TBL_SUPER 0x11D /* Time Base Lower Supervisor for writing */

#define DEC   0x016 /* Decrement */
#define DECAR 0x036 /* Decrement Auto-Reload */
#define TSR   0x150 /* Time Status Register */
#define TCR   0x154 /* Timer Control Register */

#define IVR   0x03F /* Interrupt Vector Prefix Register */

/*
 * Decrementer Timer (DEC)
 * Fixed Interval Timer (FIT)
 * Watch Dog Timer (WD)
 */

void timer(U32 timeout) {

        // check status of TSR (Time Status Register) ?
        // decrement exception is sent to interrupt mechanism.
        // register exception handler for this.

        U32 upper = 0x0;
        U32 lower = 0x1;

        asm("mfspr %0, %1" : "=r" (upper) : "r" (TBU_USER));
        asm("mfspr %0, %1" : "=r" (lower) : "r" (TBL_USER));
        
        printf("0x%u%u\n", upper, lower);
}