clk_get(NULL,"adc")可以获得adc时钟,每一个外设都有自己的工作频率,
PRSCVL是A/D转换器时钟的预分频功能时A/D时钟的计算公式
A/D时钟 = PCLK / (PRSCVL+1),
注意:AD时钟最大为2.5MHZ并且应该小于PCLK的1/5
clk_get从一个时钟list链表中以字符id名称来查找一个时钟clk结构体并且返回,最后调用clk.enable(),来时能对应的外设时钟源。
clk_get(NULL,"adc"),函数的第二个参数adc是在内核2.2.12中的arch/arm/mach-s3c2410/clock.c文件中定义的
/* clock definitions */
static struct clk init_clocks[] = {
{ .name = "nand",
.id = -1,
.parent = &clk_h,
.enable = s3c24xx_clkcon_enable,
.ctrlbit = S3C2410_CLKCON_NAND
},
{ .name = "lcd",
.id = -1,
.parent = &clk_h,
.enable = s3c24xx_clkcon_enable,
.ctrlbit = S3C2410_CLKCON_LCDC
},
{ .name = "usb-host",
.id = -1,
.parent = &clk_h,
.enable = s3c24xx_clkcon_enable,
.ctrlbit = S3C2410_CLKCON_USBH
},
{ .name = "usb-device",
.id = -1,
.parent = &clk_h,
.enable = s3c24xx_clkcon_enable,
.ctrlbit = S3C2410_CLKCON_USBD
},
{ .name = "timers",
.id = -1,
.parent = &clk_p,
.enable = s3c24xx_clkcon_enable,
.ctrlbit = S3C2410_CLKCON_PWMT
},
{ .name = "sdi",
.id = -1,
.parent = &clk_p,
.enable = s3c24xx_clkcon_enable,
.ctrlbit = S3C2410_CLKCON_SDI
},
{ .name = "uart",
.id = 0,
.parent = &clk_p,
.enable = s3c24xx_clkcon_enable,
.ctrlbit = S3C2410_CLKCON_UART0
},
{ .name = "uart",
.id = 1,
.parent = &clk_p,
.enable = s3c24xx_clkcon_enable,
.ctrlbit = S3C2410_CLKCON_UART1
},
{ .name = "uart",
.id = 2,
.parent = &clk_p,
.enable = s3c24xx_clkcon_enable,
.ctrlbit = S3C2410_CLKCON_UART2
},
{ .name = "gpio",
.id = -1,
.parent = &clk_p,
.enable = s3c24xx_clkcon_enable,
.ctrlbit = S3C2410_CLKCON_GPIO
},
{ .name = "rtc",
.id = -1,
.parent = &clk_p,
.enable = s3c24xx_clkcon_enable,
.ctrlbit = S3C2410_CLKCON_RTC
},
{ .name = "adc",
.id = -1,
.parent = &clk_p,
.enable = s3c24xx_clkcon_enable,
.ctrlbit = S3C2410_CLKCON_ADC
},
{ .name = "i2c",
.id = -1,
.parent = &clk_p,
.enable = s3c24xx_clkcon_enable,
.ctrlbit = S3C2410_CLKCON_IIC
},
{ .name = "iis",
.id = -1,
.parent = &clk_p,
.enable = s3c24xx_clkcon_enable,
.ctrlbit = S3C2410_CLKCON_IIS
},
{ .name = "spi",
.id = -1,
.parent = &clk_p,
.enable = s3c24xx_clkcon_enable,
.ctrlbit = S3C2410_CLKCON_SPI
},
{ .name = "watchdog",
.id = -1,
.parent = &clk_p,
.ctrlbit = 0
}
};