BeRTOS
|
00001 00038 #include "clock_sam3.h" 00039 #include <cfg/compiler.h> 00040 #include <cfg/macros.h> 00041 #include <io/sam3.h> 00042 00043 00044 /* Frequency of board main oscillator */ 00045 #define BOARDOSC_FREQ 12000000 00046 00047 /* Timer countdown timeout for clock initialization operations */ 00048 #define CLOCK_TIMEOUT 0xFFFFFFFF 00049 00050 00051 #if CPU_FREQ == 84000000 || CPU_FREQ == 48000000 00052 00053 INLINE uint32_t evaluate_pll(void) 00054 { 00055 return CKGR_PLLR_MUL(CPU_FREQ / BOARDOSC_FREQ * 2 - 1) | CKGR_PLLR_DIV(2); 00056 } 00057 00058 #else 00059 00060 #warning CPU clock frequency non-standard setting: multiplier and divider values \ 00061 will be computed at runtime: effective computed frequency could be different \ 00062 from expected. 00063 00064 /* 00065 * Try to evaluate the correct divider and multiplier value depending 00066 * on the desired CPU frequency. 00067 * 00068 * We try all combinations in a certain range of divider and multiplier 00069 * values. Start with higher multipliers and divisors, generally better. 00070 */ 00071 INLINE uint32_t evaluate_pll(void) 00072 { 00073 int mul, div, best_mul, best_div; 00074 int best_delta = CPU_FREQ; 00075 int freq = 0; 00076 00077 for (mul = 13; mul > 0; mul--) 00078 { 00079 for (div = 24; div > 0; div--) 00080 { 00081 freq = BOARDOSC_FREQ / div * (1 + mul); 00082 if (ABS((int)CPU_FREQ - freq) < best_delta) { 00083 best_delta = ABS((int)CPU_FREQ - freq); 00084 best_mul = mul; 00085 best_div = div; 00086 } 00087 } 00088 } 00089 00090 return CKGR_PLLR_DIV(best_div) | CKGR_PLLR_MUL(best_mul); 00091 } 00092 00093 #endif /* CPU_FREQ */ 00094 00095 void clock_init(void) 00096 { 00097 uint32_t timeout; 00098 00099 /* Disable watchdog */ 00100 WDT_MR = BV(WDT_WDDIS); 00101 00102 /* Set wait states for flash access, needed for higher CPU clock rates */ 00103 EEFC0_FMR = EEFC_FMR_FWS(3); 00104 #ifdef EEFC1_FMR 00105 EEFC1_FMR = EEFC_FMR_FWS(3); 00106 #endif 00107 00108 // Initialize main oscillator 00109 if (!(CKGR_MOR & BV(CKGR_MOR_MOSCSEL))) 00110 { 00111 CKGR_MOR = CKGR_MOR_KEY(0x37) | CKGR_MOR_MOSCXTST(0x8) 00112 | BV(CKGR_MOR_MOSCRCEN) | BV(CKGR_MOR_MOSCXTEN); 00113 timeout = CLOCK_TIMEOUT; 00114 while (!(PMC_SR & BV(PMC_SR_MOSCXTS)) && --timeout); 00115 } 00116 00117 // Switch to external oscillator 00118 CKGR_MOR = CKGR_MOR_KEY(0x37) | CKGR_MOR_MOSCXTST(0x8) 00119 | BV(CKGR_MOR_MOSCRCEN) | BV(CKGR_MOR_MOSCXTEN) | BV(CKGR_MOR_MOSCSEL); 00120 timeout = CLOCK_TIMEOUT; 00121 while (!(PMC_SR & BV(PMC_SR_MOSCXTS)) && --timeout); 00122 00123 // Initialize and enable PLL clock 00124 CKGR_PLLR = evaluate_pll() | BV(CKGR_PLLR_STUCKTO1) | CKGR_PLLR_PLLCOUNT(0x2); 00125 timeout = CLOCK_TIMEOUT; 00126 while (!(PMC_SR & BV(PMC_SR_LOCK)) && --timeout); 00127 00128 PMC_MCKR = PMC_MCKR_CSS_MAIN_CLK; 00129 timeout = CLOCK_TIMEOUT; 00130 while (!(PMC_SR & BV(PMC_SR_MCKRDY)) && --timeout); 00131 00132 PMC_MCKR = PMC_MCKR_CSS_PLL_CLK; 00133 timeout = CLOCK_TIMEOUT; 00134 while (!(PMC_SR & BV(PMC_SR_MCKRDY)) && --timeout); 00135 00136 /* Enable clock on PIO for inputs */ 00137 // TODO: move this in gpio_init() for better power management? 00138 pmc_periphEnable(PIOA_ID); 00139 pmc_periphEnable(PIOB_ID); 00140 pmc_periphEnable(PIOC_ID); 00141 #ifdef PIOF_ID 00142 pmc_periphEnable(PIOD_ID); 00143 pmc_periphEnable(PIOE_ID); 00144 pmc_periphEnable(PIOF_ID); 00145 #endif 00146 }