diff --git a/cpu/arm926ejs/at91/clock.c b/cpu/arm926ejs/at91/clock.c
index 444d42d..b06d760 100644
--- a/cpu/arm926ejs/at91/clock.c
+++ b/cpu/arm926ejs/at91/clock.c
@@ -157,9 +157,10 @@ int at91_clock_init(unsigned long main_clock)
 	 */
 	if (!main_clock) {
 		do {
-			tmp = at91_sys_read(AT91_CKGR_MCFR);
-		} while (!(tmp & AT91_PMC_MAINRDY));
-		main_clock = (tmp & AT91_PMC_MAINF) * (AT91_SLOW_CLOCK / 16);
+			tmp = readl(&pmc->mcfr);
+		} while (!(tmp & AT91_PMC_MCFR_MAINRDY));
+		tmp &= AT91_PMC_MCFR_MAINF_MASK;
+		main_clock = tmp * (AT91_SLOW_CLOCK / 16);
 	}
 #endif
 	main_clk_rate_hz = main_clock;
diff --git a/include/asm-arm/arch-at91/at91_pmc.h b/include/asm-arm/arch-at91/at91_pmc.h
index 369b5d7..680fe33 100644
--- a/include/asm-arm/arch-at91/at91_pmc.h
+++ b/include/asm-arm/arch-at91/at91_pmc.h
@@ -71,6 +71,9 @@ typedef struct at91_pmc {
 #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