#define AT91_PMC_PLLBR_USBDIV_2 0x10000000
#define AT91_PMC_PLLBR_USBDIV_4 0x20000000
+#define AT91_PMC_MCFR_MAINRDY 0x00010000
+#define AT91_PMC_MCFR_MAINF_MASK 0x0000FFFF
+
#define AT91_PMC_MCKR_CSS_SLOW 0x00000000
#define AT91_PMC_MCKR_CSS_MAIN 0x00000001
#define AT91_PMC_MCKR_CSS_PLLA 0x00000002