+#define AT91_PMC_PCR_GCKCSS (0x7 << 8)
+#define AT91_PMC_PCR_GCKCSS_SLOW_CLK (0x0 << 8)
+#define AT91_PMC_PCR_GCKCSS_MAIN_CLK (0x1 << 8)
+#define AT91_PMC_PCR_GCKCSS_PLLA_CLK (0x2 << 8)
+#define AT91_PMC_PCR_GCKCSS_UPLL_CLK (0x3 << 8)
+#define AT91_PMC_PCR_GCKCSS_MCK_CLK (0x4 << 8)
+#define AT91_PMC_PCR_GCKCSS_AUDIO_CLK (0x5 << 8)