在智龙2上GPIO6 GPIO92产生PWM波
方案一：利用 LED_PWM(1) PWM0 PWM1 分析原始功能没有复用 LS1X_PWM0_BASE0x1fe5c000 此处是物理地址0xbfefc0000 为核心虚地址空间的程序空间地址 使用的平台文件 pwm.c中 这就需要在内核配置时，添加以下选项： 添加了HAVE_PWM后，就有了平台设备pwm_device的定义 ls1x_pwm_list (2)内核中选择Loongson 1Cboard的CPU 则在pwm.c中定义了外部的ls1x_pwm_list，分析驱动pwm.c 这个变量在平台文件中定义，分析ls1c300a_openloongson_v2.0_platform.c 下面看leds_pwm在drivers/leds/ 下的makefile, leds_pwm的编译依赖于 CONFIG_LEDS_PWM. CONFIG_LEDS_PWM 在内核配置中的出现依赖于HAVE_PWM配置项 其中， struct pwm_device 在文件 linux-3.0.82-openloongson\linux-3.0.82-openloongson\arch\mips\include\asm\mach-loongson\ls1x\ls1x_pwm.h #ifndef __ASM_ARCH_LS1X_PWM_H#define __ASM_ARCH_LS1X_PWM_H struct pwm_device { unsignedint id; unsignedint gpio; boolused;}; #endif /* __ASM_ARCH_LS1X_PWM_H */ （3）Linux内核配置选中pwm驱动Machine selection --->Systemtype(Loongson family of machines) --->MacineType(Loongson 1C board)--->[ ] loongson 1c v2[*] Enable PWM 在LED类中配置PWMDevice Drivers --->[*] LED Support ---> <*>PWM driven LED Support 在平台文件ls1c300a_openloongson_v2.0_platform.c 中添加： #ifdef CONFIG_LEDS_PWMstatic struct led_pwm ls1x_pwm_leds[] = { { .name = "ls1x_pwm_led1", .pwm_id = 0, .max_brightness= 255, .pwm_period_ns = 7812500, }, { .name = "ls1x_pwm_led2", .pwm_id = 1, .max_brightness= 255, .pwm_period_ns = 7812500, },}; static struct led_pwm_platform_data ls1x_pwm_data ={ .num_leds= ARRAY_SIZE(ls1x_pwm_leds), .leds = ls1x_pwm_leds,}; static struct platform_device ls1x_leds_pwm = { .name = "leds_pwm", .id =-1, .dev = { .platform_data= &ls1x_pwm_data, },}; #endif //#ifdef CONFIG_LEDS_PWM上一个平台文件中，函数static struct platform_device *ls1b_platform_devices[]__initdata中添加：#ifdef CONFIG_LEDS_PWM &ls1x_leds_pwm,#endif平台文件增加成功：leds_pwm 将PWM0 占比调到最大(高电平占100%)echo 255 > brightness 将PWM0 占比调到最小(低电平占100%)echo 0 > brightness编译成功后，编写测试代码：
#include <stdio.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#define CMD_PWM_GET _IO('c',0x01)
#define CMD_PWM_START _IO('c',0x02)
#define CMD_PWM_STOP _IO('c',0x03)
//sel为选择PWM通道(0或者1);value为占空比(0-100);freq为频率().
int pwmset(unsigned int sel, unsigned int value, unsigned int freq) {
int fd;
//data的值代表的是高电平脉冲所占的时钟数，data的值代表的是低电平脉冲所占的时钟数
unsigned int data = {0x7ffffff,0x7ffffff};
if(value>100)
value = 100;
data = freq / 100 * value;
data = freq / 100 * (100-value);
printf("cys: ready to open!\n");
fd = open("/dev/ls1f-pwm",O_RDWR);
sleep(2);
if (fd != -1)
{
printf("open ok!\n");
//共有四路pwm(pwm0...pwm3)，四路pwm可同时工作，也可选择使用其中任何一路
if (sel <0 || sel > 3)
return -1;
switch(sel) {
case 0:
//在驱动中没有用到ioctl的第三个参数，故直接赋予0就可以啦
ioctl(fd, CMD_PWM_START , 0);
write(fd, data, sizeof(data) );
break;
case 1:
ioctl(fd, CMD_PWM_START , 1);
write(fd, data, sizeof(data) );
break;
case 2:
ioctl(fd, CMD_PWM_START , 2);
write(fd, data, sizeof(data) );
break;
case 3:
ioctl(fd, CMD_PWM_START , 3);
write(fd, data, sizeof(data) );
break;
default:
break;
}
}
else
{
printf("Device open failure\n");
}
sleep(10);
close(fd);
return 0;
}
调用函数 pwmset(0,50,10000) 意思是在PWM0引脚产生占空比 50%, 周期10000时钟周期的波形。 方案二：自己编写驱动文件
首先在平台文件中添加资源：
平台文件\arch\mips\loongson\ls1x\ls1c\ls1c300a_openloongson_v2.0_platform.c添加：
#ifdef CONFIG_LS1C_PWM_DRIVER
static struct resource ls1c_pwm0_resource[] = {
={
.start= LS1X_PWM0_BASE,
.end = (LS1X_PWM0_BASE + 0x0f),
.flags = IORESOURCE_MEM,
},
={
.start= LS1X_PWM1_BASE,
.end = (LS1X_PWM1_BASE + 0x0f),
.flags = IORESOURCE_MEM,
},
={
.start= LS1X_PWM2_BASE,
.end = (LS1X_PWM2_BASE + 0x0f),
.flags = IORESOURCE_MEM,
},
={
.start= LS1X_PWM3_BASE,
.end = (LS1X_PWM3_BASE + 0x0f),
.flags = IORESOURCE_MEM,
},
};
static struct platform_device ls1c_pwm_device = {
.name = "ls1c-pwm",
.id = -1,
.num_resources = ARRAY_SIZE(ls1c_pwm0_resource),
.resource = ls1c_pwm0_resource,
};
#endif //#ifdef CONFIG_LS1C_PWM_DRIVER
上一个文件中，函数 static struct platform_device *ls1b_platform_devices[] __initdata中添加：
#ifdef CONFIG_LS1C_PWM_DRIVER
&ls1c_pwm_device,
#endif
在 \drivers\char\Kconfig中添加：
config LS1C_PWM_DRIVER
bool "ls1c pwm driver"
default n
help
pwm.
在 char 下的Makefile文件中添加语句：
obj-$(CONFIG_LS1C_PWM_DRIVER) += ls1c-pwm.o
平台设备增加成功：ls1c-pwm
编写驱动文件 ls1c_pwm.c（根据1B中的资料修改）， 放到内核代码driver/char下，
修改Makefile文件，添加语句：obj-$(CONFIG_LS1C_PWM_DRIVER) += ls1c-pwm.o
以下 设备驱动ls1c_pwm.c 代码：
/*ls1c_pwm.c*/
#include <linux/miscdevice.h>
#include <linux/errno.h>
#include <linux/fs.h>
#include <asm/io.h>
#include <asm/uaccess.h>
#include <asm/ioctl.h>
#include <linux/platform_device.h>
#include <linux/timer.h>
#define CMD_PWM_GET _IO('c',0x01)
#define CMD_PWM_START _IO('c',0x02)
#define CMD_PWM_STOP _IO('c',0x03)
#define REG_PWM_CNTR0x00 // 0xBFE5C010
#define REG_PWM_HRC 0x04 // 0xBFE5C014
#define REG_PWM_LRC 0x08 // 0xBFE5C018
#define REG_PWM_CTRL0x0c// 0xBFE5C01C
#define REG_GPIO_CFG00xbfd010c0//GPIO GPIO 配置寄存器 1 表示配置为GPIO， 0 表示无效
#define REG_GPIO_CFG20xbfd010c8//GPIO 配置寄存器 1 表示配置为GPIO， 0 表示无效
#define SB2F_GPIO_MUX_CTRL1 0xbfd00424//功能复用寄存器
static unsigned char __iomem *pwm_base = NULL;
struct resource *res;
static int ls1f_pwm_probe(struct platform_device *pdev);
struct platform_device *pwm_dev;
struct resource *res1 = NULL;
static int ls1f_pwm_getResourse(struct platform_device *pdev, unsigned int index);
static struct platform_driver ls1f_pwm_driver = {
.probe = ls1f_pwm_probe,
.driver = {
.name = "ls1c-pwm",
},
};
static int ls1f_pwm_open(struct inode *inode, struct file *file)
{
//配置PWM0 PWM1 原始功能没有复用
//long val = readl(SB2F_GPIO_MUX_CTRL1);
//val &= 0xfffffffc;
//writel(val, SB2F_GPIO_MUX_CTRL1);
long val = readl(REG_GPIO_CFG0);
//配置GPIO6引脚为普通功能，而非GPIO功能
val &= 0xffffffbf;
writel(val, REG_GPIO_CFG0);
val = readl(REG_GPIO_CFG0);
//配置GPIO92引脚为普通功能，而非GPIO功能
val &= 0xefffffff;
writel(val, REG_GPIO_CFG2);
return 0;
}
static int ls1f_pwm_close(struct inode *inode, struct file *file)
{
writel(0x0, pwm_base + REG_PWM_CTRL);
return 0;
}
static ssize_t ls1f_pwm_read(struct file *file, char __user *buf, size_t count, loff_t *ptr)
{
unsigned int pwm_val;
pwm_val = readl(pwm_base);
if (copy_to_user(buf, &pwm_val, sizeof(unsigned int)))
return -EFAULT;
return 4;
}
static ssize_t ls1f_pwm_write(struct file *file, const char __user *buf, size_t count, loff_t *ptr)
{
unsigned int hrc_val, lrc_val;
unsigned int data = {0x0};
if (copy_from_user(data, buf, sizeof(data)))
{
printk("Write error!\n");
return -EIO;
}
hrc_val = data - 1;
lrc_val = data + data -1;
//设置占空比
writel(hrc_val, pwm_base + REG_PWM_HRC);
writel(lrc_val, pwm_base + REG_PWM_LRC);
printk("hrc:%i ; lrc:%i\n",hrc_val,lrc_val);
return 0;
}
static int pwm_start_stop(unsigned int cmd, unsigned long arg)
{
printk("into: %s\n", __FUNCTION__);
printk("arg: %ld\n", arg);
if (arg > 3)
return -1;
//从platform中获取指定PWM的寄存器基址 pwm_base
//通过改变arg，实现在pwm0、pwm1、pwm2、pwm3之间切换
ls1f_pwm_getResourse(pwm_dev, arg);
switch (cmd) {
//启动PWM
case CMD_PWM_START:
printk("CMD_PWM_START\n");
writel(0x0, pwm_base + REG_PWM_CNTR);
writel(0x01, pwm_base + REG_PWM_CTRL);
break;
//停止PWM
case CMD_PWM_STOP:
printk("CMD_PWM_STOP\n");
writel(0x0, pwm_base + REG_PWM_CTRL);
break;
default:
break;
}
return 0;
}
static long ls1f_pwm_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
{
printk("into %s\n", __FUNCTION__);
printk("cmd: %d\n", cmd);
printk("arg: %ld\n", arg);
if (arg > 3)
return -1;
switch (cmd) {
case CMD_PWM_GET:
ls1f_pwm_getResourse(pwm_dev, arg);
break;
case CMD_PWM_START:
case CMD_PWM_STOP:
return pwm_start_stop(cmd, arg);
default:
break;
}
return 0;
}
static const struct file_operations ls1f_pwm_ops = {
.owner = THIS_MODULE,
.open = ls1f_pwm_open,
.release = ls1f_pwm_close,
.read = ls1f_pwm_read,
.write = ls1f_pwm_write,
.unlocked_ioctl = ls1f_pwm_ioctl,
};
static struct miscdevice ls1f_pwm_miscdev = {
MISC_DYNAMIC_MINOR,
"ls1f-pwm",
&ls1f_pwm_ops,
};
static int ls1f_pwm_getResourse(struct platform_device *pdev, unsigned int index)
{
res = platform_get_resource(pdev, IORESOURCE_MEM, index);
if (res == NULL)
{
printk("Fail to get ls1f_pwm_resource!\n");
return -ENOENT;
}
printk("Resource start=0x%x, end = 0x%x\n", res->start, res->end);
if (res1 != NULL)
{
release_mem_region(res->start, 0x0f);
}
res1 = request_mem_region(res->start, 0x0f, "ls1f-pwm");
if (res1 == NULL)
{
printk("Fail to request ls1f_pwm region!\n");
return -ENOENT;
}
pwm_base = ioremap(res->start, res->end - res->start + 1);
if (pwm_base == NULL)
{
printk("Fail to ioremap ls1f_pwm resource!\n");
return -EINVAL;
}
return 0;
}
static int __devinit ls1f_pwm_probe(struct platform_device *pdev)
{
pwm_dev = pdev;
return ls1f_pwm_getResourse(pdev, 1);
}
static int __init ls1f_pwm_init(void) {
if (misc_register(&ls1f_pwm_miscdev))
{
printk(KERN_WARNING "pwm: Couldn't register device 10, %d.\n", 255);
return -EBUSY;
}
return platform_driver_register(&ls1f_pwm_driver);
}
static void __exit ls1f_pwm_exit(void)
{
misc_deregister(&ls1f_pwm_miscdev);
release_mem_region(res->start, 0x20);
platform_driver_unregister(&ls1f_pwm_driver);
}
module_init(ls1f_pwm_init);
module_exit(ls1f_pwm_exit);
MODULE_AUTHOR("sundm");
MODULE_DESCRIPTION("loongson 1C PWM driver");
MODULE_LICENSE("GPL");
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