本文共 11772 字,大约阅读时间需要 39 分钟。
总盯着过去,你会瞎掉一只眼;然而忘掉历史,你会双目失明。
阅读IMX6ULL的参考手册,我们可以知道IMX6ULL共有 5 组 GPIO( GPIO1~GPIO5),每组引脚最多有 32 个,但是可能实际上并没有那么多。
组别 | 引脚 |
---|---|
GPIO1 有 32 个引脚: | GPIO1_IO0~GPIO1_IO31; |
GPIO2 有 22 个引脚: | GPIO2_IO0~GPIO2_IO21; |
GPIO3 有 29 个引脚: | GPIO3_IO0~GPIO3_IO28; |
GPIO4 有 29 个引脚: | GPIO4_IO0~GPIO4_IO28; |
GPIO5 有 12 个引脚: | GPIO5_IO0~GPIO5_IO11; |
GPIO 的控制涉及 3 大模块: CCM、 IOMUXC、 GPIO 模块本身,框图如下:
GPIOx 要用 CCM_CCGRy 寄存器中的 2 位来决定该组 GPIO 是否使能。各组GPIO的具体时钟控制寄存器如下所示。
GPIO2时钟控制寄存器
GPIO3时钟控制寄存器
GPIO4时钟控制寄存器
而CCM_CCGR 寄存器中某 2 位的取值含义如下:
一个引脚寄存器 | 作用 |
---|---|
IOMUXC_SW_ MUX _ CTL_PAD_< PADNAME > | 选择某个 引脚的复用模式 |
IOMUXC_SW_ PAD _ CTL_PAD_< PADNAME > | 选择某个 引脚的电气属性 |
一个引脚对应一个寄存器(前缀MUX)
每个引脚都有8个可选的模式(alternate (ALT) MUX_MODE)
顺便一提,上图中的loopback 功能(回环测试)。设置该引脚的 loopback 功能,这样就可以从 GPIOx_PSR 中读到引脚的有实电平!
因为从 GPIOx_DR 中读回的只是上次设置的值,它并不能反应引脚的真实电平。假若硬件故障导致该引脚与地短路了,通过设置 GPIOx_DR让它输出高电平并不会起效果,这时我们通过读取GPIOx_PSR便可知道该引脚的真实输出状态!
也是一个引脚对应一个寄存器(前缀PAD)
设置电气属性
框图如下
主要关心3个寄存器:
② GPIOx_DR:设置输出引脚的电平,每位对应一个引脚, 1-高电平, 0-低电平
③ GPIOx_PSR:读取引脚的电平,每位对应一个引脚, 1-高电平, 0-低电平
上一节的Hello驱动,并没有实际操作硬件,而LED点灯驱动操作硬件势在必行。这时就有一个问题需要考虑了,APP应用程序只是调用驱动程序的接口,这个不涉及具体硬件,所以无可厚非。而驱动程序肯定要操作硬件,这时如果把硬件的寄存器操作与驱动程序混在一起编写,那么我们的驱动程序的可移植性将会变得特别差。当硬件发生变动时,我们需要更改驱动程序!这显然不是我们想要的结果,那怎么样才能实现应用程序通用,驱动程序也通用呢?分层!
即把驱动拆分为通用的框架(leddrv.c)、具体的硬件操作(board_X.c),如下图所示。分别为不同板子,编写具体的硬件操作代码!每个单板的具体硬件操作分为:LED初始化(board_led_init)和LED控制(board_led_ctrl)!而这两个函数我们又可以将其定义为一个结构体,供上层的leddrv.c调用,于是下图所示框架。
leddrv.c
#include#include #include #include #include #include #include #include #include #include #include #include #include #include #include #include "led_opr.h"/* 1. 确定主设备号 */static int major = 0;static struct class *led_class;struct led_operations *p_led_opr;/* 3. 实现对应的open/read/write等函数,填入file_operations结构体 */static int led_drv_open (struct inode *node, struct file *file){ /* 根据node确次设备号 */ int minor = iminor(node); /* 根据次设备号初始化LED */ p_led_opr->init(minor); return 0;}static int led_drv_close (struct inode *node, struct file *file){ return 0;}static ssize_t led_drv_read (struct file *file, char __user *buf, size_t size, loff_t *offset){ return 0;}/* write(fd, &val, 1); */static ssize_t led_drv_write (struct file *file, const char __user *buf, size_t size, loff_t *offset){ int err; char status; struct inode *node = file_inode(file); int minor = iminor(node); err = copy_from_user(&status, buf, 1); /* 根据次设备号和status控制LED */ p_led_opr->ctl(minor, status); return 1;}/* 2. 定义自己的file_operations结构体 */static struct file_operations led_drv = { .owner = THIS_MODULE, .open = led_drv_open, .read = led_drv_read, .write = led_drv_write, .release = led_drv_close,};/* 5. 谁来注册驱动程序啊?得有一个入口函数:安装驱动程序时,就会去调用这个入口函数 */static int __init led_init(void){ int err; int i; printk("LED init \r\n"); /* 4. 把file_operations结构体告诉内核:注册驱动程序 */ major = register_chrdev(0, "led", &led_drv); /* /dev/led */ /* 7. 其他完善:提供设备信息,自动创建设备节点 */ led_class = class_create(THIS_MODULE, "led_class"); err = PTR_ERR(led_class); if (IS_ERR(led_class)) { unregister_chrdev(major, "led"); return -1; } /* 注意要在创建设备之前获得led_operaions结构体(需要用到其中的num) */ p_led_opr = get_board_led_opr(); for (i = 0; i < p_led_opr->num; i++) device_create(led_class, NULL, MKDEV(major, i), NULL, "led%d", i); /* /dev/led0,1,... */ return 0;}/* 6. 有入口函数就应该有出口函数:卸载驱动程序时,就会去调用这个出口函数 */static void __exit led_exit(void){ int i; printk("LED exit \r\n"); for (i = 0; i < p_led_opr->num; i++) device_destroy(led_class, MKDEV(major, i)); /* /dev/led0,1,... */ class_destroy(led_class); unregister_chrdev(major, "led");}module_init(led_init);module_exit(led_exit);MODULE_LICENSE("GPL");
LED驱动程序说明:
iminor(node)
获得设备的此设备号file_inode(file)
获得node节点,然后再通过iminor(node)
获得设备的次设备号!board_qemu.c
#include#include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include "led_opr.h"/* 需要理解开始偏移23个int,即23x4=92=0x5C * IOMUXC_SW_MUX_CTL_PAD_GPIO1_IO00 地址是 20E_0000h base + 5Ch */struct iomux { volatile unsigned int unnames[23]; volatile unsigned int IOMUXC_SW_MUX_CTL_PAD_GPIO1_IO00; /* offset 0x5c*/ volatile unsigned int IOMUXC_SW_MUX_CTL_PAD_GPIO1_IO01; volatile unsigned int IOMUXC_SW_MUX_CTL_PAD_GPIO1_IO02; volatile unsigned int IOMUXC_SW_MUX_CTL_PAD_GPIO1_IO03; volatile unsigned int IOMUXC_SW_MUX_CTL_PAD_GPIO1_IO04; volatile unsigned int IOMUXC_SW_MUX_CTL_PAD_GPIO1_IO05; volatile unsigned int IOMUXC_SW_MUX_CTL_PAD_GPIO1_IO06; volatile unsigned int IOMUXC_SW_MUX_CTL_PAD_GPIO1_IO07; volatile unsigned int IOMUXC_SW_MUX_CTL_PAD_GPIO1_IO08; volatile unsigned int IOMUXC_SW_MUX_CTL_PAD_GPIO1_IO09;};struct imx6ull_gpio { volatile unsigned int dr; volatile unsigned int gdir; volatile unsigned int psr; volatile unsigned int icr1; volatile unsigned int icr2; volatile unsigned int imr; volatile unsigned int isr; volatile unsigned int edge_sel;};/* enable GPIO1,GPIO5 他们两个都是由CCGR1来控制的!*/static volatile unsigned int *CCM_CCGR1; /* set GPIO5_IO03 as GPIO 值得一提的是,IOMUXC_SNVS_SW_MUX_CTL_PAD_SNVS_TAMPER3复用时只有一种即GPIO5_IO03*/static volatile unsigned int *IOMUXC_SNVS_SW_MUX_CTL_PAD_SNVS_TAMPER3;/* set GPIO1_IO03 as GPIO */static struct iomux *iomux;static struct imx6ull_gpio *gpio1;static struct imx6ull_gpio *gpio5;static int board_qemu_led_init (int which) /* 初始化LED, which-哪个LED */ { if (!CCM_CCGR1) { CCM_CCGR1 = ioremap(0x20C406C, 4); IOMUXC_SNVS_SW_MUX_CTL_PAD_SNVS_TAMPER3 = ioremap(0x2290014, 4); iomux = ioremap(0x20E0000, sizeof(struct iomux)); gpio1 = ioremap(0x209C000, sizeof(struct imx6ull_gpio)); gpio5 = ioremap(0x20AC000, sizeof(struct imx6ull_gpio)); } if (which == 0) { /* 1. enable GPIO5 * CG15, b[31:30] = 0b11 */ *CCM_CCGR1 |= (3<<30); /* 2. set GPIO5_IO03 as GPIO * MUX_MODE, b[3:0] = 0b101 */ *IOMUXC_SNVS_SW_MUX_CTL_PAD_SNVS_TAMPER3 = 5; /* 3. set GPIO5_IO03 as output * GPIO5 GDIR, b[3] = 0b1 */ gpio5->gdir |= (1<<3); } else if(which == 1) { /* 1. enable GPIO1 * CG13, b[27:26] = 0b11 */ *CCM_CCGR1 |= (3<<26); /* 2. set GPIO1_IO03 as GPIO * MUX_MODE, b[3:0] = 0b101 */ iomux->IOMUXC_SW_MUX_CTL_PAD_GPIO1_IO03 = 5; /* 3. set GPIO1_IO03 as output * GPIO1 GDIR, b[3] = 0b1 */ gpio1->gdir |= (1<<3); } else if(which == 2) { /* 1. enable GPIO1 * CG13, b[27:26] = 0b11 */ *CCM_CCGR1 |= (3<<26); /* 2. set GPIO1_IO05 as GPIO * MUX_MODE, b[3:0] = 0b101 */ iomux->IOMUXC_SW_MUX_CTL_PAD_GPIO1_IO05 = 5; /* 3. set GPIO1_IO05 as output * GPIO1 GDIR, b[5] = 0b1 */ gpio1->gdir |= (1<<5); } else if(which == 3) { /* 1. enable GPIO1 * CG13, b[27:26] = 0b11 */ *CCM_CCGR1 |= (3<<26); /* 2. set GPIO1_IO06 as GPIO * MUX_MODE, b[3:0] = 0b101 */ iomux->IOMUXC_SW_MUX_CTL_PAD_GPIO1_IO06 = 5; /* 3. set GPIO1_IO06 as output * GPIO1 GDIR, b[6] = 0b1 */ gpio1->gdir |= (1<<6); } //printk("%s %s line %d, led %d\n", __FILE__, __FUNCTION__, __LINE__, which); return 0;}static int board_qemu_led_ctl (int which, char status) /* 控制LED, which-哪个LED, status:1-亮,0-灭 */{ //printk("%s %s line %d, led %d, %s\n", __FILE__, __FUNCTION__, __LINE__, which, status ? "on" : "off"); if (which == 0) { if (status) /* on : output 0 */ gpio5->dr &= ~(1<<3); else /* on : output 1 */ gpio5->dr |= (1<<3); } else if (which == 1) { if (status) /* on : output 0 */ gpio1->dr &= ~(1<<3); else /* on : output 1 */ gpio1->dr |= (1<<3); } else if (which == 2) { if (status) /* on : output 0 */ gpio1->dr &= ~(1<<5); else /* on : output 1 */ gpio1->dr |= (1<<5); } else if (which == 3) { if (status) /* on : output 0 */ gpio1->dr &= ~(1<<6); else /* on : output 1 */ gpio1->dr |= (1<<6); } return 0;}static struct led_operations board_qemu_led_opr = { .num = 4, .init = board_qemu_led_init, .ctl = board_qemu_led_ctl,};struct led_operations *get_board_led_opr(void){ return &board_qemu_led_opr;}
单板程序编程步骤
GPIO单板控制说明
led_opr.h
#ifndef _LED_OPR_H#define _LED_OPR_Hstruct led_operations { int num; /* num-LED数量 */ int (*init) (int which); /* 初始化LED, which-哪个LED */ int (*ctl) (int which, char status); /* 控制LED, which-哪个LED, status:1-亮,0-灭 */};struct led_operations *get_board_led_opr(void);#endif
led_operations 需要说明的:
ledtest.c
#include#include #include #include #include #include /* * ./ledtest /dev/led0 on * ./ledtest /dev/led0 off */int main(int argc, char **argv){ int fd; char status; /* 1. 判断参数 */ if (argc != 3) { printf("Usage: %s \n", argv[0]); return -1; } /* 2. 打开文件 */ fd = open(argv[1], O_RDWR); if (fd == -1) { printf("can not open file %s\n", argv[1]); return -1; } /* 3. 写文件 */ if (0 == strcmp(argv[2], "on")) { status = 1; write(fd, &status, 1); } else { status = 0; write(fd, &status, 1); } close(fd); return 0;}
应用程序需要说明的是:
Makefile
KERN_DIR = /home/clay/linux/qemu/kernel/100ask_imx6ull-qemu/linux-4.9.88all: make -C $(KERN_DIR) M=`pwd` modules $(CROSS_COMPILE)gcc -o ledtest ledtest.c clean: make -C $(KERN_DIR) M=`pwd` modules clean rm -rf modules.order rm -f ledtest# 参考内核源码drivers/char/ipmi/Makefile# 要想把a.c, b.c编译成ab.ko, 可以这样指定:# ab-y := a.o b.o# obj-m += ab.o# leddrv.c board_qemu.c 编译成 led.koled-y := leddrv.o board_qemu.oobj-m += led.o
Makefile需要说明的:
编译程序没有问题后,运行qemu虚拟开发板,并做好准备工作!将
cp *.ko ledtest ~/linux/qemu/NFS/
insmod led.ko
./ledtest /dev/led0 on
./ledtest /dev/led0 off
其余三盏灯,操作分别用led1 led2 led3即可,这里不再一一演示。
需要注意的是,如果使用正点原子开发板点亮LED之前,要先关闭设备树中的自带LED,屏蔽内容如下图。
cp -rf *.ko led ~/nfs/rootfs/lib/modules/4.1.15/
depmod //第一次加载驱动的时候需要运行此命令
modprobe led.ko //加载驱动
./led /dev/led1 on
./led /dev/led1 off
rmmod led.ko
嘻嘻,好长的一篇~
转载地址:http://lfnaf.baihongyu.com/