linux-2.2.12内核之clk_get()函数浅析

最新推荐文章于 2022-08-14 09:47:40 发布

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本文介绍了如何使用clk_get函数获取ADC时钟，并详细解释了A/D转换器时钟的预分频功能及其计算公式。此外，还展示了内核中与ADC时钟相关的具体实现细节。

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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
}
};