xip_elapsed_since
#define xip_elapsed_since(x) (signed)((~xip_omap_mpu_timer_read(0) - (x)) / 6)
#define xip_elapsed_since(x) (signed)((readl_relaxed(OSCR) - (x)) / 4)
#define xip_elapsed_since(x) ((xtensa_get_sr(ccount) - (x)) / 1000) /* should work up to 1GHz */
#define xip_elapsed_since(x) (0)