Add support for switching clock to different sources (see atmel datasheet for detail).

git-svn-id: https://src.develer.com/svnoss/bertos/trunk@1222 38d2e660-2303-0410-9eaa-f027e97ec537

diff --git a/bertos/cpu/arm/hw/crtat91sam7_rom.S b/bertos/cpu/arm/hw/crtat91sam7_rom.S
index 0a2fa4a791be63a6c3fbe0b246cb1bb6c756654a..a889680dd6f5b280bef89bf2836090a4cb17a7e5 100644 (file)
--- a/bertos/cpu/arm/hw/crtat91sam7_rom.S
+++ b/bertos/cpu/arm/hw/crtat91sam7_rom.S
@@ -79,7 +79,7 @@
 #endif
 
 
-#if CPU_ARM_AT91SAM7S256 || CPU_ARM_AT91SAM7X256
+#if CPU_ARM_AT91SAM7S256 || CPU_ARM_AT91SAM7X256 || CPU_ARM_AT91SAM7X128
        /**
        * With a 18.420MHz cristal, master clock is:
        * (((18.420 * PLL_MUL_VAL + 1) / PLL_DIV_VAL) / AT91MCK_PRES) = 48.023MHz
@@ -110,7 +110,9 @@
        #define PMC_MOSCS             (1 << 0)
        #define PMC_LOCK              (1 << 2)
        #define PMC_MCKRDY            (1 << 3)
+       #define PMC_CSS_MASK        0x00000003
        #define PMC_CSS_PLL_CLK     0x00000003
+       #define PMC_PRES_MASK       0x0000001C
        #define PMC_PRES_CLK_2      0x00000004
 
        #define CKGR_MOR_OFF        0x00000020
@@ -228,6 +230,28 @@ wait_moscs:
         tst     r0, #PMC_MOSCS
         beq     wait_moscs
 
+        /*
+         * Switch to Slow oscillator clock.
+         */
+        ldr     r0, [r1, #PMC_MCKR_OFF]
+        and     r0, r0, #~PMC_CSS_MASK
+        str     r0, [r1, #PMC_MCKR_OFF]
+wait_slowosc:
+        ldr     r0, [r1, #PMC_SR_OFF]
+        tst     r0, #PMC_MCKRDY
+        beq     wait_slowosc
+
+        /*
+         * Switch to prescaler div 1 factor.
+         */
+        ldr     r0, [r1, #PMC_MCKR_OFF]
+        and     r0, r0, #~PMC_PRES_MASK
+        str     r0, [r1, #PMC_MCKR_OFF]
+wait_presc:
+        ldr     r0, [r1, #PMC_SR_OFF]
+        tst     r0, #PMC_MCKRDY
+        beq     wait_presc
+
         /*
          * Set PLL:
          * PLLfreq = crystal / divider * (multiplier + 1)