Davinci DM6446 Linux 内核分析—— clock.c
http://www.61ic.com/Article/DaVinci/DM644X/201201/40303.html
/* 该文件中到程序实现了各模块PSC的管理，时钟的初始化、注册、获取以及使能等 */
/**************************************************************************
* Included Files
**************************************************************************/
#include <linux/config.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/fs.h>
#include <linux/major.h>
#include <linux/root_dev.h>
#include <asm/setup.h>
#include <asm/semaphore.h>
#include <asm/hardware/clock.h>
#include <asm/io.h>
#include <asm/mach-types.h>
#include <asm/mach/arch.h>
#include <asm/mach/map.h>
#include <asm/arch/hardware.h>
#include <asm/arch/cpu.h>
#include <asm/arch/mux.h>
#include "clock.h"
#define PLL1_PLLM __REG(0x01c40910)
#define PLL2_PLLM __REG(0x01c40D10)
#define PTCMD __REG(0x01C41120)
#define PDSTAT __REG(0x01C41200)
#define PDCTL1 __REG(0x01C41304)
#define EPCPR __REG(0x01C41070)
#define PTSTAT __REG(0x01C41128)
#define MDSTAT IO_ADDRESS(0x01C41800)
#define MDCTL IO_ADDRESS(0x01C41A00)
#define VDD3P3V_PWDN __REG(0x01C40048)
static LIST_HEAD(clocks); // 链表头，用于管理所有到时钟结构体
static DECLARE_MUTEX(clocks_sem); // 添加和删除时钟用到信号量，用来互斥
static DEFINE_RAW_SPINLOCK(clockfw_lock);
static unsigned int commonrate;
static unsigned int div_by_four;
static unsigned int div_by_six;
static unsigned int div_by_eight;
static unsigned int armrate;
static unsigned int fixedrate;
/*
* 正如下面英文解释所说的，board_setup_psc函数用于使能和禁止某个PSC域，
* 共有两个域DSP和ARM,在include/asm-arm/arch-davinci/hardware.h
* 中定义。如果要使用某个模块到功能，比如SPI，则必须先使用该函数，打开该
* 模块的电源和时钟，然后才可以设置其寄存器和操作。
*/
/**************************************
Routine: board_setup_psc
Description: Enable/Disable a PSC domain
**************************************/
void board_setup_psc(unsigned int domain, unsigned int id, char enable)
{
volatile unsigned int *mdstat = (unsigned int *)((int)MDSTAT + 4 * id);
volatile unsigned int *mdctl = (unsigned int *)((int)MDCTL + 4 * id);
if (enable) {
*mdctl |= 0x00000003; /* Enable Module */
} else {
*mdctl &= 0xFFFFFFF2; /* Disable Module */
}
if ((PDSTAT & 0x00000001) == 0) {
PDCTL1 |= 0x1;
PTCMD = (1 << domain);
while ((((EPCPR >> domain) & 1) == 0)) ;
PDCTL1 |= 0x100;
while (!(((PTSTAT >> domain) & 1) == 0)) ;
} else {
PTCMD = (1 << domain);
while (!(((PTSTAT >> domain) & 1) == 0)) ;
}
if (enable) {
while (!((*mdstat & 0x0000001F) == 0x3)) ;
} else {
while (!((*mdstat & 0x0000001F) == 0x2)) ;
}
}
/*
* 获取时钟结构体指针
* 从链表中获取时钟结构体指针，比较时钟名（字符串），如果相同就返回该结构体指针
*/
struct clk *clk_get(struct device *dev, const char *id)
{
struct clk *p, *clk = ERR_PTR(-ENOENT);
down(&clocks_sem);
list_for_each_entry(p, &clocks, node) {
if (strcmp(id, p->name) == 0 && try_module_get(p->owner)) {
clk = p;
break;
}
}
up(&clocks_sem);
return clk;
}
/* 导出该符号，以便其它驱动程序调用 */
EXPORT_SYMBOL(clk_get);
/* 将时钟结构体放回到链表中，以便其它驱动能够获得 */
void clk_put(struct clk *clk)
{
if (clk && !IS_ERR(clk))
module_put(clk->owner); // 减少模块使用计数,模块使用计数的介绍可参考本站转载的文章《Linux kernel-2.6 模块使用计数》
}
EXPORT_SYMBOL(clk_put);
/* 打开模块的电源和时钟 */
int __clk_enable(struct clk *clk)
{
if (clk->flags & ALWAYS_ENABLED) // 检查是否已经打开
return 0;
board_setup_psc(DAVINCI_GPSC_ARMDOMAIN, clk->lpsc, 1); // 1代表使能
return 0;
}
/* 关闭模块的电源和时钟 */
void __clk_disable(struct clk *clk)
{
if (clk->usecount) // 检查模块是否正在被使用
return;
board_setup_psc(DAVINCI_GPSC_ARMDOMAIN, clk->lpsc, 0); // 0代表关闭
}
/* 减少时钟引用计数 */
void __clk_unuse(struct clk *clk)
{
if (clk->usecount > 0) {
--clk->usecount;
}
}
/* 增加时钟引用计数 */
int __clk_use(struct clk *clk)
{
int ret = 0;
clk->usecount++;
return ret;
}
/* __clk_enable函数的封装，其它驱动可调用。 */
int clk_enable(struct clk *clk)
{
unsigned long flags;
int ret;
spin_lock_irqsave(&clockfw_lock, flags); // 关中断和多CPU占用
ret = __clk_enable(clk);
spin_unlock_irqrestore(&clockfw_lock, flags);
if (davinci_pinmux_setup)
davinci_pinmux_setup(clk->lpsc); /* 打开其引脚到模块功能，dm644x各模块到功能引脚大多和GPIO功能复用，
故使用前要初始化，默认是模块功能一脚而非GPIO */
else
printk (KERN_WARNING "WARNING davinci_pinmux_setup "
"uninitialized\n");
return ret;
}
EXPORT_SYMBOL(clk_enable);
/* __clk_disable函数的封装 */
void clk_disable(struct clk *clk)
{
unsigned long flags;
spin_lock_irqsave(&clockfw_lock, flags);
__clk_disable(clk);
spin_unlock_irqrestore(&clockfw_lock, flags);
}
EXPORT_SYMBOL(clk_disable);
/* __clk_use函数的封装 */
int clk_use(struct clk *clk)
{
unsigned long flags;
int ret = 0;
spin_lock_irqsave(&clockfw_lock, flags);
ret = __clk_use(clk);
spin_unlock_irqrestore(&clockfw_lock, flags);
return ret;
}
EXPORT_SYMBOL(clk_use);
/* __clk_unuse函数的封装 */
void clk_unuse(struct clk *clk)
{
unsigned long flags;
spin_lock_irqsave(&clockfw_lock, flags);
__clk_unuse(clk);
spin_unlock_irqrestore(&clockfw_lock, flags);
}
EXPORT_SYMBOL(clk_unuse);
/* 获取模块时钟的频率 */
unsigned long clk_get_rate(struct clk *clk)
{
return *(clk->rate);
}
EXPORT_SYMBOL(clk_get_rate);
/* 添加时钟到链表中 */
int clk_register(struct clk *clk)
{
down(&clocks_sem);
list_add(&clk->node, &clocks);
up(&clocks_sem);
return 0;
}
EXPORT_SYMBOL(clk_register);
/* 将时钟从链表中清除 */
void clk_unregister(struct clk *clk)
{
down(&clocks_sem);
list_del(&clk->node);
up(&clocks_sem);
}
EXPORT_SYMBOL(clk_unregister);
/* dm644x平台所有模块的时钟*/
static struct clk davinci_dm644x_clks[] = {
{
.name = "ARMCLK", // 时钟名，ARM域的时钟
.rate = &armrate,
.lpsc = -1,
.flags = ALWAYS_ENABLED,
},
{
.name = "UART0",
.rate = &fixedrate,
.lpsc = DAVINCI_LPSC_UART0,
.usecount = 1,
},
{
.name = "EMACCLK",
.rate = &commonrate,
.lpsc = DAVINCI_LPSC_EMAC_WRAPPER,
},
{
.name = "I2CCLK",
.rate = &fixedrate,
.lpsc = DAVINCI_LPSC_I2C,
},
{
.name = "IDECLK",
.rate = &commonrate,
.lpsc = DAVINCI_LPSC_ATA,
},
{
.name = "McBSPCLK0",
.rate = &commonrate,
.lpsc = DAVINCI_LPSC_McBSP0,
},
{
.name = "MMCSDCLK0",
.rate = &commonrate,
.lpsc = DAVINCI_LPSC_MMC_SD0,
},
{
.name = "SPICLK",
.rate = &commonrate,
.lpsc = DAVINCI_LPSC_SPI,
},
{
.name = "gpio",
.rate = &commonrate,
.lpsc = DAVINCI_LPSC_GPIO,
},
{
.name = "AEMIFCLK",
.rate = &commonrate,
.lpsc = DAVINCI_LPSC_AEMIF,
.usecount = 1,
},
{
.name = "PWM0_CLK",
.rate = &fixedrate,
.lpsc = DAVINCI_LPSC_PWM0,
},
{
.name = "PWM1_CLK",
.rate = &fixedrate,
.lpsc = DAVINCI_LPSC_PWM1,
},
{
.name = "PWM2_CLK",
.rate = &fixedrate,
.lpsc = DAVINCI_LPSC_PWM2,
},
{
.name = "USBCLK",
.rate = &commonrate,
.lpsc = DAVINCI_LPSC_USB,
},
};
/* dm6467平台所有模块的时钟*/
static struct clk davinci_dm6467_clks[] = {
{
.name = "ARMCLK",
.rate = &armrate,
.lpsc = -1,
.flags = ALWAYS_ENABLED,
},
{
.name = "UART0",
.rate = &fixedrate,
.lpsc = DAVINCI_DM646X_LPSC_UART0,
.usecount = 1,
},
{
.name = "UART1",
.rate = &fixedrate,
.lpsc = DAVINCI_DM646X_LPSC_UART1,
.usecount = 1,
},
{
.name = "UART2",
.rate = &fixedrate,
.lpsc = DAVINCI_DM646X_LPSC_UART2,
.usecount = 1,
},
{
.name = "EMACCLK",
.rate = &div_by_four,
.lpsc = DAVINCI_DM646X_LPSC_EMAC,
},
{
.name = "I2CCLK",
.rate = &div_by_four,
.lpsc = DAVINCI_DM646X_LPSC_I2C,
},
{
.name = "IDECLK",
.rate = &div_by_six,
.lpsc = DAVINCI_LPSC_ATA,
},
{
.name = "McASPCLK0",
.rate = &div_by_four,
.lpsc = DAVINCI_DM646X_LPSC_McASP0,
},
{
.name = "McASPCLK1",
.rate = &div_by_four,
.lpsc = DAVINCI_DM646X_LPSC_McASP1,
},
{
.name = "SPICLK",
.rate = &div_by_four,
.lpsc = DAVINCI_DM646X_LPSC_SPI,
},
{
.name = "AEMIFCLK",
.rate = &div_by_four,
.lpsc = DAVINCI_DM646X_LPSC_AEMIF,
.usecount = 1,
},
{
.name = "PWM0_CLK",
.rate = &div_by_four,
.lpsc = DAVINCI_DM646X_LPSC_PWM0,
},
{
.name = "PWM1_CLK",
.rate = &div_by_four,
.lpsc = DAVINCI_DM646X_LPSC_PWM1,
},
{
.name = "USBCLK",
.rate = &div_by_four,
.lpsc = DAVINCI_LPSC_USB,
},
};
/* dm355平台所有模块的时钟*/
static struct clk davinci_dm355_clks[] = {
{
.name = "ARMCLK",
.rate = &armrate,
.lpsc = -1,
.flags = ALWAYS_ENABLED,
},
{
.name = "UART0",
.rate = &fixedrate,
.lpsc = DAVINCI_LPSC_UART0,
.usecount = 1,
},
{
.name = "UART1",
.rate = &fixedrate,
.lpsc = DAVINCI_LPSC_UART1,
.usecount = 1,
},
{
.name = "UART2",
.rate = &fixedrate,
.lpsc = DAVINCI_LPSC_UART2,
.usecount = 1,
},
{
.name = "EMACCLK",
.rate = &commonrate,
.lpsc = DAVINCI_LPSC_EMAC_WRAPPER,
},
{
.name = "I2CCLK",
.rate = &fixedrate,
.lpsc = DAVINCI_LPSC_I2C,
},
{
.name = "IDECLK",
.rate = &commonrate,
.lpsc = DAVINCI_LPSC_ATA,
},
{
.name = "McBSPCLK0",
.rate = &commonrate,
.lpsc = DAVINCI_LPSC_McBSP0,
},
{
.name = "McBSPCLK1",
.rate = &commonrate,
.lpsc = DAVINCI_LPSC_McBSP1,
},
{
.name = "MMCSDCLK0",
.rate = &commonrate,
.lpsc = DAVINCI_LPSC_MMC_SD0,
},
{
.name = "MMCSDCLK1",
.rate = &commonrate,
.lpsc = DAVINCI_LPSC_MMC_SD1,
},
{
.name = "SPICLK",
.rate = &commonrate,
.lpsc = DAVINCI_LPSC_SPI,
},
{
.name = "gpio",
.rate = &commonrate,
.lpsc = DAVINCI_LPSC_GPIO,
},
{
.name = "AEMIFCLK",
.rate = &commonrate,
.lpsc = DAVINCI_LPSC_AEMIF,
.usecount = 1,
},
{
.name = "PWM0_CLK",
.rate = &fixedrate,
.lpsc = DAVINCI_LPSC_PWM0,
},
{
.name = "PWM1_CLK",
.rate = &fixedrate,
.lpsc = DAVINCI_LPSC_PWM1,
},
{
.name = "PWM2_CLK",
.rate = &fixedrate,
.lpsc = DAVINCI_LPSC_PWM2,
},
{
.name = "PWM3_CLK",
.rate = &fixedrate,
.lpsc = DAVINCI_LPSC_PWM3,
},
{
.name = "USBCLK",
.rate = &commonrate,
.lpsc = DAVINCI_LPSC_USB,
},
};
/*
clk初始化，采用一个链表把所有到时钟结构体链接在一起，该链表的头是clocks。
davinci_clk_init()例程由io.c中的davinci_map_common_io()例程调用，后者被
davinci_map_io()例程调用，而其又被注册到board_evm.c中的机器描述符中（struct machine_desc），
故具体调用过程是：
start_kernel()-->setup_arch()-->paging_init()-->mdesc->map_io()
(其就是davinci_map_io())-->davinci_map_common_io()-->davinci_clk_init()。
*/
void davinci_clk_init(void)
{
struct clk *clkp;
static struct clk *board_clks;
int count = 0, num_clks;
if (cpu_is_davinci_dm355()) { // dm355平台时钟初始化
/*
* FIXME
* We're assuming a 24MHz reference, but the DM355 also
* supports a 36MHz reference.
*/
unsigned long postdiv;
/*
* Read the PLL1 POSTDIV register to determine if the post
* divider is /1 or /2
*/
postdiv = (davinci_readl(DAVINCI_PLL_CNTRL0_BASE + 0x128)
& 0x1f) + 1;
fixedrate = 24000000;
armrate = (PLL1_PLLM + 1) * (fixedrate / (16 * postdiv));
commonrate = armrate / 2;
board_clks = davinci_dm355_clks;
num_clks = ARRAY_SIZE(davinci_dm355_clks);
} else if (cpu_is_davinci_dm6467()) { // dm6467平台时钟初始化
fixedrate = 24000000;
div_by_four = ((PLL1_PLLM + 1) * 27000000) / 4;
div_by_six = ((PLL1_PLLM + 1) * 27000000) / 6;
div_by_eight = ((PLL1_PLLM + 1) * 27000000) / 8;
armrate = ((PLL1_PLLM + 1) * 27000000) / 2;
board_clks = davinci_dm6467_clks;
num_clks = ARRAY_SIZE(davinci_dm6467_clks);
} else { // dm644X平台时钟初始化
fixedrate = 27000000; // 平台输入频率，即晶振频率
armrate = (PLL1_PLLM + 1) * (fixedrate / 2); // arm时钟，其为DSP时钟的一半
commonrate = armrate / 3; // 其他时钟为DSP时钟的1/6，arm时钟的1/3
board_clks = davinci_dm644x_clks;
num_clks = ARRAY_SIZE(davinci_dm644x_clks);
}
for (clkp = board_clks; count < num_clks; count++, clkp++) {
clk_register(clkp); // 将时钟注册到链表中
/* Turn on clocks that have been enabled in the
* table above */
if (clkp->usecount) { // 如果该时钟已经被使用，则开启它
clk_enable(clkp); // 使能该时钟
}
}
}