达芬奇平台DM644X(ARM9, Linux-2.6.10)BSP之clock.c分析

于 2012-10-16 09:00:12 发布
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分类专栏： 硬件知识 编程 LINUX内核 ARM 文章标签： 平台 struct div domain wrapper module
本文详细介绍了达芬奇系列处理器（包括dm644X、dm6467和dm355）的时钟管理实现。通过分析源代码，展示了不同平台时钟初始化的过程，以及如何通过软件接口来启用、禁用时钟和获取时钟频率。

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                /*
* linux/arch/arm/mach-davinci/clock.c
*
* TI DaVinci clock config file
*
* Copyright (C) 2006 Texas Instruments.
*
* ----------------------------------------------------------------------------
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
* GNU General Public License for more details.
*
*  You should have received a copy of the GNU General Public License
*  along with this program; if not, write to the Free Software
*  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
* ----------------------------------------------------------------------------
*
*/

/* 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 */
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
        }
    }
}


本文来自ChinaUnix博客，如果查看原文请点：http://blog.chinaunix.net/u2/79779/showart_1356828.html
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