cmd编译c Bootloader之uBoot简介（转）(18)

以根据代码中的计算公式针对自己的开发板修改系统时钟。

下面是针对S3C2410、S3C2440，分别使用不同的宏设置系统时钟：

58 int board_init (void)

59 {

60 S3C24X0_CLOCK_POWER * const clk_power = S3C24X0_GetBase_CLOCK_POWER();

61 S3C24X0_GPIO * const gpio = S3C24X0_GetBase_GPIO();

62

63 /* 设置GPIO */

64 gpio->GPACON = 0x007FFFFF;

65 gpio->GPBCON = 0x00044555;

66 gpio->GPBUP = 0x000007FF;

67 gpio->GPCCON = 0xAAAAAAAA;

68 gpio->GPCUP = 0x0000FFFF;

69 gpio->GPDCON = 0xAAAAAAAA;

70 gpio->GPDUP = 0x0000FFFF;

71 gpio->GPECON = 0xAAAAAAAA;

72 gpio->GPEUP = 0x0000FFFF;

73 gpio->GPFCON = 0x000055AA;

74 gpio->GPFUP = 0x000000FF;

75 gpio->GPGCON = 0xFF95FFBA;

76 gpio->GPGUP = 0x0000FFFF;

77 gpio->GPHCON = 0x002AFAAA;

78 gpio->GPHUP = 0x000007FF;

79

80 /* 同时支持S3C2410和S3C2440, */

81 if ((gpio->GSTATUS1 == 0x32410000) || (gpio->GSTATUS1 == 0x32410002))

82 {

83 /* FCLK:HCLK:PCLK = 1:2:4 */

84 clk_power->CLKDIVN = S3C2410_CLKDIV;

85

86 /* 修改为异步总线模式 */

87 __asm__( "mrc p15, 0, r1, c1, c0, 0\n" /* read ctrl register */

88 "orr r1, r1, #0xc0000000\n" /* Asynchronous */

89 "mcr p15, 0, r1, c1, c0, 0\n" /* write ctrl register */

90 :::"r1"

91 );

92

93 /* 设置PLL锁定时间 */

94 clk_power->LOCKTIME = 0xFFFFFF;

95

96 /* 配置MPLL */

97 clk_power->MPLLCON = S3C2410_MPLL_200MHZ;

98

99 /* 配置MPLL后，要延时一段时间再配置UPLL */

100 delay (4000);

101

102 /* 配置UPLL */

103 clk_power->UPLLCON = S3C2410_UPLL_48MHZ;

104

105 /* 再延时一会 */

106 delay (8000);

107

108 /* 机器类型ID，这在调用Linux内核时用到 */

109 gd->bd->bi_arch_number = MACH_TYPE_SMDK2410;

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