Ti437x LED匯流排驅動模型程式+裝置樹
本文主要記錄AM437X驅動的LED。含簡單的字元裝置驅動、裝置驅動模型、裝置樹以及LED子系統。
目前就Linux驅動的理解是:
Linux驅動 = 裸機 + 框架
關於框架,目前的理解是:
以LED驅動為例,之前印象中就是韋老大的思路,現在init裡註冊、硬體初始化,然後應用層open()、read()就呼叫了file_operations裡面的drv_open()、drv_write()等,算是最簡單的驅動框架。
然後韋老大又提及了匯流排裝置驅動模型,將裝置和驅動分離,感受到了新的框架。不久前,簡單接觸了下裝置樹,感覺就是匯流排裝置驅動模型的修改(升級),將原來的裝置部分,不再單獨放在程式碼裡,而是放在dts裡面,開機載入,然後驅動匹配獲取硬體資源。因此,感覺驅動的框架在一步一步的發展,優化,最原始的註冊、open等框架,還是不變。
同時,瞭解到了除輸入子系統的其它子系統,加深了對這一模式的理解。感覺就是,將某個硬體資源無縫的融入現有的環境中,而無須改變應用層的程式。
這就是目前的一點小小理解吧,算是打開了個入口,希望以後瞭解得更加全面、細緻。
1.搭建開發環境
1.1安裝TI_SDK
先在TI官網下載ti-processor-sdk-linux-am437x-evm-01.00.00.03-Linux-x86-Install.bin
在Ubuntu(only Ubuntu 12.04 LTS and Ubuntu 14.04 LTS are supported)下,對該檔案加入可執行許可權,然後直接執行。安裝目錄選擇預設即可。完成之後,便在當前使用者的home目錄生成了所有所需檔案。
1.2編譯核心
在當前生成ti-processor-sdk-linux-am437x-evm-01.00.00.03目錄下,有個Makefile,開啟後可以看到相關的編譯選項,如:
- 編譯全部檔案:
make all
- 編譯核心:
make linux
- 編譯u-boot:
make u-boot-spl
- 以及make的依賴:
-include Rules.make
。在本層目錄裡,開啟Rules.make
,可以知道核心的預設配置檔案:
#defconfig
DEFCONFIG=tisdk_am437x-evm_defconfig
通過查詢,tisdk_am437x-evm_defconfig在~/ti-processor-sdk-linux-am437x-evm-01.00.00.03/board-support/linux-3.14.43+gitAUTOINC+875c69b2c3-g875c69b/arch/arm/configs
這裡通過修改該配置檔案,然後重新編譯核心,即可關閉系統LED相關的驅動,在後面自己寫LED驅動時,防止互相干擾。
因此將tisdk_am437x-evm_defconfig配置檔案裡的所有有關LED的配置都關閉掉。
最後在頂層目錄執行make linux
,編譯完成後,生成~/ti-processor-sdk-linux-am437x-evm-01.00.00.03/board-support/linux-3.14.43+gitAUTOINC+875c69b2c3-g875c69b/arch/arm/boot/zImage
檔案。
1.3燒寫SD卡
回到~/ti-processor-sdk-linux-am437x-evm-01.00.00.03/bin
下,TI製作了很多指令碼,其中的create-sdcard.sh
就是製作SD卡的。Ubuntu插上SD卡,然後切換成root使用者,執行該指令碼,根據提示一路選擇下去即可。
這裡燒寫完了,測試發現並沒有使用之前編譯的核心,分析指令碼後發現,該指令碼直接使用的~/ti-processor-sdk-linux-am437x-evm-01.00.00.03/filesystem
下的tisdk-rootfs-image-am437x-evm.tar.gz
。指令碼將該檔案作為根檔案系統放入SD卡,因此並沒有使用之前編譯的核心。解決方法要麼在執行指令碼的過程中根據提示輸入相關的路徑,要麼在製作好SD卡後,將編譯好的核心覆蓋掉SD卡的核心即可。我選擇的後者:cp ~/ti-processor-sdk-linux-am437x-evm-01.00.00.03/board-support/linux-3.14.43+gitAUTOINC+875c69b2c3-g875c69b/arch/arm/boot/zImage /media/hceng/rootfs/boot/
。
最後將製作好的SD卡插上開發板啟動即可。
2.簡單的字元驅動
先記錄下幾個重要型別或結構體:
- 表示裝置號(32位機中:高12位表示主裝置號,低20位表示次裝置號)
typedef __kernel_dev_t dev_t;
- 描述字元裝置
struct cdev {
struct kobject kobj; //內嵌kobject結構體,用於裝置驅動模型管理
struct module *owner; //包含指向該結構的模組的指標,用於引用計數
const struct file_operations *ops; //指向字元裝置操作函式集的指標
struct list_head list; //該結構將使用該驅動的字元裝置連線成一個連結串列
dev_t dev; //該字元裝置的其實裝置號,一個裝置可能有多個裝置號
unsigned int count; //使用該字元裝置驅動的裝置數量
};
- 描述類
struct class{
const char *name; //類名稱
struct module *owner; //對應模組
struct subsystem subsys; //對應的subsystem;
struct list_head children; //class_device連結串列
struct list_head interfaces; //class_interface連結串列
struct semaphore sem; /用於同步的訊號鎖
struct class_attribute *class_attrs; //類屬性
int (*uevent)(struct class_device *dev,char **envp,int num_envp,
char *buffer,int buffer_size); //事件
void (*release)(struct class_device *dev); //釋放類裝置
void (*class_release)(struct class *class); //釋放類
}
總結下,目前理解的字元裝置編寫流程:
1)驅動載入函式:
xx_drv_init()
1.1)申請裝置號:alloc_chrdev_region()
1.2)cde初始化(繫結fops):cdev_init()
1.3)註冊到核心:cdev_add()
1.4)建立類:class_create()
1.5)向類中新增裝置(mdev自動建立裝置節點):device_create()
1.6)硬體相關(記憶體對映):ioremap()
2)驅動解除安裝函式:xx_drv_exit()
2.1)移除裝置:device_destroy()
2.2)移除類:class_destroy()
2.3)登出cdev:cdev_del()
2.4)釋放裝置號:unregister_chrdev()
2.5)釋放記憶體:iounmap()
3)必要修飾:module_init(xx_drv_init);module_exit(xx_drv_exit);MODULE_LICENSE("GPL");
4)構造file_operations:struct file_operations xx_drv_fops;
5)實現file_operations裡每個函式:xx_open()、xx_write()……
2.1驅動程式碼
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/fs.h>
#include <linux/init.h>
#include <asm/uaccess.h>
#include <asm/io.h>
#include <linux/device.h>
#include <linux/cdev.h>
#define TI_LEDS_CNT 4
int major;
static struct cdev leds_cdev;
static struct class *leds_cls;
static volatile unsigned long *PRCM_CM_PER_GPIO5_CLKCTRL = NULL;
static volatile unsigned long *CTRL_CONF_UART3_RXD = NULL;
static volatile unsigned long *CTRL_CONF_UART3_TXD = NULL;
static volatile unsigned long *CTRL_CONF_UART3_CTSN = NULL;
static volatile unsigned long *CTRL_CONF_UART3_RTSN = NULL;
static volatile unsigned long *GPIO_OE = NULL;
static volatile unsigned long *GPIO_SETDATAOUT = NULL;
static volatile unsigned long *GPIO_DATAOUT = NULL;
static int leds_drv_open(struct inode *inode, struct file *file)
{
int minor = iminor(file->f_inode);
printk(KERN_INFO"%s OK.\n",__func__);
*PRCM_CM_PER_GPIO5_CLKCTRL = (0x01<<1);
*CTRL_CONF_UART3_RXD &= ~(0x7<<0 | 0x01<<16 | 0x01<<17 | 0x01<<18);
*CTRL_CONF_UART3_RXD |= (0x7<<0 | 0x01<<17);
*GPIO_OE &= ~(0x01<<minor);
*GPIO_SETDATAOUT |= (0x01<<minor);
return 0;
}
static ssize_t leds_drv_write(struct file *file, const char __user *user_buf, size_t count, loff_t * ppos)
{
int minor = iminor(file->f_inode);
char buf;
printk(KERN_INFO"%s OK.\n",__func__);
if(count != 1){
printk(KERN_INFO"write count != 1.\n");
return 1;
}
if (copy_from_user(&buf, user_buf, count))
return -EFAULT;
if (0x01 == buf)
*GPIO_DATAOUT |= (0x01<<minor);
else if(0x00 == buf)
*GPIO_DATAOUT &= ~(0x01<<minor);
return 0;
}
static struct file_operations leds_fops = {
.owner = THIS_MODULE,
.open = leds_drv_open,
.write = leds_drv_write,
};
static int leds_drv_init(void)
{
//1.申請裝置號
dev_t devid;
printk(KERN_INFO"%s OK.\n",__func__);
if(alloc_chrdev_region(&devid, 0, TI_LEDS_CNT, "ti_leds") < 0)
{
printk(KERN_INFO"%s ERROR.\n",__func__);
goto error;
}
major = MAJOR(devid);
//2.註冊到系統中
cdev_init(&leds_cdev, &leds_fops);
cdev_add(&leds_cdev, devid, TI_LEDS_CNT);
leds_cls = class_create(THIS_MODULE, "ti_leds");
device_create(leds_cls, NULL, MKDEV(major, 0), NULL, "ti_led0");
device_create(leds_cls, NULL, MKDEV(major, 1), NULL, "ti_led1");
device_create(leds_cls, NULL, MKDEV(major, 2), NULL, "ti_led2");
device_create(leds_cls, NULL, MKDEV(major, 3), NULL, "ti_led3");
//3.硬體相關
PRCM_CM_PER_GPIO5_CLKCTRL = ioremap(0x44DF8800+0x498, 0x04*1);
CTRL_CONF_UART3_RXD = ioremap(0x44E10000+0xA28, 0x04*4);
CTRL_CONF_UART3_TXD = CTRL_CONF_UART3_RXD + 1;
CTRL_CONF_UART3_CTSN = CTRL_CONF_UART3_RXD + 2;
CTRL_CONF_UART3_RTSN = CTRL_CONF_UART3_RXD + 3;
GPIO_OE = ioremap(0x48322000+0x134, 0x04);
GPIO_DATAOUT = ioremap(0x48322000+0x13C, 0x04);
GPIO_SETDATAOUT = ioremap(0x48322000+0x194, 0x04);
error:
unregister_chrdev_region(MKDEV(major, 0), TI_LEDS_CNT);
return 0;
}
static void leds_drv_exit(void)
{
unsigned i;
printk(KERN_INFO"%s OK.\n",__func__);
for(i=0;i<TI_LEDS_CNT;i++)
{
device_destroy(leds_cls, MKDEV(major, i));
}
class_destroy(leds_cls);
cdev_del(&leds_cdev);
unregister_chrdev(major, "ti_leds");
iounmap(PRCM_CM_PER_GPIO5_CLKCTRL);
iounmap(CTRL_CONF_UART3_RXD);
iounmap(GPIO_OE);
iounmap(GPIO_DATAOUT);
iounmap(GPIO_SETDATAOUT);
}
module_init(leds_drv_init);
module_exit(leds_drv_exit);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("hceng <[email protected]>");
MODULE_DESCRIPTION("TI am437x board leds drvice");
MODULE_ALIAS("character device:ti_leds");
MODULE_VERSION("V1.0");
2.2測試程式碼(跑馬燈)
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdio.h>
#include <unistd.h>
#define msleep(x) usleep(x*1000)
int main(int argc, char **argv)
{
int fd[4];
int val = 0;
int i = 0;
//const char *dev[] = {"/dev/ti_led0", "/dev/ti_led1", "/dev/ti_led2", "/dev/ti_led3"};
const char *dev[] = {"/dev/ti_led2", "/dev/ti_led0", "/dev/ti_led3", "/dev/ti_led1"};
for(i=0; i<4; i++)
{
fd[i] = open(dev[i], O_RDWR);
if (fd[i] < 0)
{
printf("can't open %s\n", *dev[i]);
return 0;
}
}
//leds off all.
for(i=0; i<4; i++)
{
write(fd[i], &val, 1);
}
//flicker leds.
while(1)
{
val = !val;
for(i=0; i<4; i++)
{
write(fd[i], &val, 1);
msleep(300);
}
}
}
2.3關於printk除錯
核心的printk定義瞭如下的列印等級:
#define KERN_EMERG "<0>" /* system is unusable */
#define KERN_ALERT "<1>" /* action must be taken immediately */
#define KERN_CRIT "<2>" /* critical conditions */
#define KERN_ERR "<3>" /* error conditions */
#define KERN_WARNING "<4>" /* warning conditions */
#define KERN_NOTICE "<5>" /* normal but significant condition */
#define KERN_INFO "<6>" /* informational */
#define KERN_DEBUG "<7>" /* debug-level messages */
- 如果使用串列埠登陸,可通過修改/proc/sys/kernel/printk裡的引數進行設定:
echo "8 4 1 7" >/proc/sys/kernel/printk
上面的四個數字分別代表:
控制檯日誌級別:優先順序[s1] 高於該值的訊息將被列印至控制檯,[s1]數值越小,優先順序越高;
預設的訊息日誌級別:將用該優先順序來列印沒有優先順序的訊息;
最低的控制檯日誌級別:控制檯日誌級別可被設定的最小值(最高優先順序);
預設的控制檯日誌級別:控制檯日誌級別的預設值;
- 如果使用SSH登陸,是無法顯示printk的列印資訊的,但列印的資料會被放在
/var/log/messages
和/proc/kmsg
中,利用這一特性,可以後臺執行tail命令進行偵測:
tail -f /var/log/messages &
缺點是不能設定列印等級,同時核心的其它資訊也會被打印出來。
3.裝置驅動模型驅動
關於裝置驅動模型前面以及有點了解,在寫驅動的時候,主要體現在將原本的硬體資源資訊抽取了出來,單獨放在了一個檔案裡,當兩個檔案的分別載入的時候,根據名字匹配,匹配成功則呼叫probe()函式,進行類似前面的init()進行初始化。其它的內容基本一樣,該幹嘛就幹嘛。
3.1驅動程式碼
#include <linux/init.h>
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/fs.h>
#include <linux/delay.h>
#include <asm/uaccess.h>
#include <asm/irq.h>
#include <asm/io.h>
#include <linux/device.h>
#include <linux/platform_device.h>
/**************************************************
TI_BOARD
---------------------------------------------------
Ball Color Mode Pin
---------------------------------------------------
H24 D7_Blue 0x07 uart3_txd(GPIO5_3)
H25 D8_Blue 0x07 uart3_rxd(GPIO5_2)
K24 D9_Green 0x07 uart3_rtsn(GPIO5_1)
H22 D10_Red 0x07 uart3_ctsn(GPIO5_0)
**************************************************/
static struct resource leds_resource[] = {
//PRCM_CM_PER_GPIO5_CLKCTRL(498h)
[0] = {
.start = 0x44DF8800,
.end = 0x44DFFFFF,
.name = "CM_PER",
.flags = IORESOURCE_MEM,
},
//CTRL_CONF_UART3_RXD(A28h)、CTRL_CONF_UART3_TXD(A2Ch)、CTRL_CONF_UART3_CTSN(A30h)、CTRL_CONF_UART3_RTSN((A34h))
[1] = {
.start = 0x44E10000,
.end = 0x44E1FFFF,
.name = "CONTROL_MODULE",
.flags = IORESOURCE_MEM,
},
//GPIO_OE(134h)、GPIO_SETDATAOUT(194h)、GPIO_DATAOUT(13Ch)
[2] = {
.start = 0x48322000,
.end = 0x48322FFF,
.name = "GOIP5",
.flags = IORESOURCE_MEM,
},
[3] = {
.start = 0,
.end = 3,
.name = "GOIP5_PIN",
.flags = IORESOURCE_IO,
}
};
static void leds_release(struct device * dev)
{
printk(KERN_INFO"%s OK.\n",__func__);
}
static struct platform_device leds_dev = {
.name = "ti_am437x_leds_platform",
.id = -1,
.num_resources = ARRAY_SIZE(leds_resource),
.resource = leds_resource,
.dev = {
.release = leds_release,
},
};
static int leds_dev_init(void)
{
printk(KERN_INFO"%s OK.\n",__func__);
return platform_device_register(&leds_dev);;
}
static void leds_dev_exit(void)
{
printk(KERN_INFO"%s OK.\n",__func__);
platform_device_unregister(&leds_dev);
}
module_init(leds_dev_init);
module_exit(leds_dev_exit);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("hceng <[email protected]>");
MODULE_DESCRIPTION("TI am437x board leds drvice");
MODULE_ALIAS("platform:ti_leds");
MODULE_VERSION("V2.0");
#include <linux/module.h>
#include <linux/version.h>
#include <linux/init.h>
#include <linux/fs.h>
#include <linux/interrupt.h>
#include <linux/irq.h>
#include <linux/sched.h>
#include <linux/pm.h>
#include <linux/sysctl.h>
#include <linux/proc_fs.h>
#include <linux/delay.h>
#include <linux/platform_device.h>
#include <linux/input.h>
#include <linux/irq.h>
#include <asm/uaccess.h>
#include <asm/io.h>
#include <linux/cdev.h>
#include <asm/uaccess.h>
#define TI_LEDS_CNT 4
int major;
static struct cdev leds_cdev;
static struct class *leds_cls;
static volatile unsigned long *PRCM_CM_PER_GPIO5_CLKCTRL = NULL;
static volatile unsigned long *CTRL_CONF_UART3_RXD = NULL;
static volatile unsigned long *CTRL_CONF_UART3_TXD = NULL;
static volatile unsigned long *CTRL_CONF_UART3_CTSN = NULL;
static volatile unsigned long *CTRL_CONF_UART3_RTSN = NULL;
static volatile unsigned long *GPIO_OE = NULL;
static volatile unsigned long *GPIO_SETDATAOUT = NULL;
static volatile unsigned long *GPIO_DATAOUT = NULL;
static int leds_drv_open(struct inode *inode, struct file *file)
{
int minor = iminor(file->f_inode);
printk(KERN_INFO"%s OK.\n",__func__);
*PRCM_CM_PER_GPIO5_CLKCTRL = (0x01<<1);
*CTRL_CONF_UART3_RXD &= ~(0x7<<0 | 0x01<<16 | 0x01<<17 | 0x01<<18);
*CTRL_CONF_UART3_RXD |= (0x7<<0 | 0x01<<17);
*GPIO_OE &= ~(0x01<<minor);
*GPIO_SETDATAOUT |= (0x01<<minor);
return 0;
}
static ssize_t leds_drv_write(struct file *file, const char __user *user_buf, size_t count, loff_t * ppos)
{
int minor = iminor(file->f_inode);
char buf;
printk(KERN_INFO"%s OK.\n",__func__);
if(count != 1){
printk(KERN_INFO"write count != 1.\n");
return 1;
}
if (copy_from_user(&buf, user_buf, count))
return -EFAULT;
if (0x01 == buf)
*GPIO_DATAOUT |= (0x01<<minor);
else if(0x00 == buf)
*GPIO_DATAOUT &= ~(0x01<<minor);
return 0;
}
static struct file_operations leds_fops = {
.owner = THIS_MODULE,
.open = leds_drv_open,
.write = leds_drv_write,
};
static int leds_probe(struct platform_device *pdev)
{
struct resource *res;
dev_t devid;
printk(KERN_INFO"%s OK.\n",__func__);
//1.申請裝置號
if(alloc_chrdev_region(&devid, 0, TI_LEDS_CNT, "ti_leds") < 0)
{
printk("%s ERROR\n",__func__);
goto error;
}
major = MAJOR(devid);
//2.註冊到系統中
cdev_init(&leds_cdev, &leds_fops);
cdev_add(&leds_cdev, devid, TI_LEDS_CNT);
leds_cls = class_create(THIS_MODULE, "ti_leds");
device_create(leds_cls, NULL, MKDEV(major, 0), NULL, "ti_led0");
device_create(leds_cls, NULL, MKDEV(major, 1), NULL, "ti_led1");
device_create(leds_cls, NULL, MKDEV(major, 2), NULL, "ti_led2");
device_create(leds_cls, NULL, MKDEV(major, 3), NULL, "ti_led3");
//3.硬體相關
res = platform_get_resource_byname(pdev, IORESOURCE_MEM, "CM_PER");
if (!res)
return -EINVAL;
PRCM_CM_PER_GPIO5_CLKCTRL = ioremap(res->start+0x498, 0x04*1);
res = platform_get_resource_byname(pdev, IORESOURCE_MEM, "CONTROL_MODULE");
if (!res)
return -EINVAL;
CTRL_CONF_UART3_RXD = ioremap(res->start+0xA28, 0x04*4);
CTRL_CONF_UART3_TXD = CTRL_CONF_UART3_RXD + 1;
CTRL_CONF_UART3_CTSN = CTRL_CONF_UART3_RXD + 2;
CTRL_CONF_UART3_RTSN = CTRL_CONF_UART3_RXD + 3;
res = platform_get_resource_byname(pdev, IORESOURCE_MEM, "GOIP5");
if (!res)
return -EINVAL;
GPIO_OE = ioremap(res->start+0x134, 0x04);
GPIO_DATAOUT = ioremap(res->start+0x13C, 0x04);
GPIO_SETDATAOUT = ioremap(res->start+0x194, 0x04);
*PRCM_CM_PER_GPIO5_CLKCTRL = (0x01<<1);//使能GPIO外設時鐘
error:
unregister_chrdev_region(MKDEV(major, 0), TI_LEDS_CNT);
return 0;
}
static int leds_remove(struct platform_device *pdev)
{
unsigned i;
printk(KERN_INFO"%s OK.\n",__func__);
for(i=0;i<TI_LEDS_CNT;i++)
{
device_destroy(leds_cls, MKDEV(major, i));
}
class_destroy(leds_cls);
cdev_del(&leds_cdev);
unregister_chrdev(major, "ti_leds");
iounmap(PRCM_CM_PER_GPIO5_CLKCTRL);
iounmap(CTRL_CONF_UART3_RXD);
iounmap(GPIO_OE);
iounmap(GPIO_DATAOUT);
iounmap(GPIO_SETDATAOUT);
return 0;
}
struct platform_driver leds_drv = {
.probe = leds_probe,
.remove = leds_remove,
.driver = {
.name = "ti_am437x_leds_platform",
}
};
static int leds_drv_init(void)
{
printk(KERN_INFO"%s OK.\n",__func__);
return platform_driver_register(&leds_drv);
}
static void leds_drv_exit(void)
{
printk(KERN_INFO"%s OK.\n",__func__);
platform_driver_unregister(&leds_drv);
}
module_init(leds_drv_init);
module_exit(leds_drv_exit);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("hceng <[email protected]>");
MODULE_DESCRIPTION("TI am437x board leds drvice");
MODULE_ALIAS("platform:ti_leds");
MODULE_VERSION("V2.0");
測試程式同前面的一樣。
4.裝置樹驅動
4.1初識裝置樹
1)前面的匯流排裝置驅動模型中,硬體資源來自於leds_dev.c裡面的資訊,這樣會導致不同的板子,會新增不同的硬體資源資訊,造成核心的臃腫。
2)使用裝置樹後,核心不再包含硬體的描述,硬體描述放在單獨的DTS裡面,然後編譯成二進位制的DTB,在U-Boot啟動的時候載入進去,然後核心進行解析。
3)DTS、DTC和DTB之間的關係:
DTS經過DTC編譯得到DTB,DTB通過DTC反編譯得到DTS.
4)ARM中,所有的DTS檔案放在
arch/arm/boot/dts
目錄中,為了簡化,將Soc公用部分提取了出來作為dtsi,類似標頭檔案。
5)DTC編譯工具的原始碼在scripts/dtc目錄中,編譯核心時,編譯核心時,需要使能才能將原始碼編譯成工具,對應於scripts/dtc/Makefile
中"hostprogs-y:=dtc"
。Ubuntu也可直接安裝DTC工具:
sudo apt-get install device-tree-compiler
6)核心的
arch/arm/boot/dts/Makefile
中,描述了當某種Soc被選中後,哪些.dtb會編譯出來。執行make dtbs
,會根據arch/arm/Makefile
編譯指定目標。
7)單獨編譯與反編譯:
./scripts/dtc/dtc -I dts -O dtb -o xxx.dtb arch/arm/boot/dts/xxx.dts //dts->dtb
./scripts/dtc/dtc -I dtb -O dts -o xxx.dts arch/arm/boot/dts/xxx.dtb //dtb->dts
8)後面認識深刻了,再總結總結。
4.2修改AM437x裝置樹
AM437x的裝置樹檔案在~/ti-processor-sdk-linux-am437x-evm-01.00.00.03/board-support/linux-3.14.43+gitAUTOINC+875c69b2c3-g875c69b/arch/arm/boot/dts/
中,主要是am4372.dtsi和am437x-sk-evm.dts。
- 我的目的是希望寫個裝置樹框架的LED程式,因此想讓am437x-sk-evm.dts乾淨點,只包含LED硬體描述,因此我需要刪除am437x-sk-evm.dts裡面的其它硬體描述。經過測試,am437x-sk-evm.dts裡面包含部分MMC的描述,一旦刪除將不能成功啟動核心。而且,後面除錯的時候,希望開發板通過NFS掛載的方式,直接載入編譯的驅動模組,因此需要保留網絡卡描述部分。最後,將MMC和網絡卡必須的部分,提取了出來,放在了am4372.dtsi中。精簡後的am437x-sk-evm.dts內容如下:
/* AM437x SK EVM */
/dts-v1/;
#include "am4372.dtsi"
#include <dt-bindings/pinctrl/am43xx.h>
#include <dt-bindings/gpio/gpio.h>
/ {
model = "TI AM437x SK EVM";
compatible = "ti,am437x-sk-evm","ti,am4372","ti,am43";
led_pin {
compatible = "ti_leds";
pinctrl-names = "default";
pinctrl-0 = <&leds_pins>;
am437x,led_gpio0 = <&gpio5 0 GPIO_ACTIVE_HIGH>;
am437x,led_gpio1 = <&gpio5 1 GPIO_ACTIVE_HIGH>;
am437x,led_gpio2 = <&gpio5 2 GPIO_ACTIVE_HIGH>;
am437x,led_gpio3 = <&gpio5 3 GPIO_ACTIVE_HIGH>;
};
};
&am43xx_pinmux {
leds_pins: leds_pins {
pinctrl-single,pins = <
0x228 (PIN_OUTPUT | MUX_MODE7) /* uart3_rxd.gpio5_2 */
0x22c (PIN_OUTPUT | MUX_MODE7) /* uart3_txd.gpio5_3 */
0x230 (PIN_OUTPUT | MUX_MODE7) /* uart3_ctsn.gpio5_0 */
0x234 (PIN_OUTPUT | MUX_MODE7) /* uart3_rtsn.gpio5_1 */
>;
};
};
&gpio5 {
status = "okay";
};
額,在除錯的過程中,需要不斷編譯新的DTB和複製到SD卡的rootfs分割槽中,仿照前面寫了個指令碼進行自動編譯和複製,同時檢查檔案的生成時間間隔,實際中,確實減少了焦躁的重複操作。
4.3驅動程式碼
#include <linux/module.h>
#include <linux/version.h>
#include <linux/init.h>
#include <linux/fs.h>
#include <linux/interrupt.h>
#include <linux/irq.h>
#include <linux/sched.h>
#include <linux/pm.h>
#include <linux/sysctl.h>
#include <linux/proc_fs.h>
#include <linux/delay.h>
#include <linux/platform_device.h>
#include <linux/input.h>
#include <linux/irq.h>
#include <asm/uaccess.h>
#include <asm/io.h>
#include <linux/cdev.h>
#include <asm/uaccess.h>
#include <linux/gpio.h>
#include <linux/of_gpio.h>
#define TI_LEDS_CNT 4
int major;
static struct cdev leds_cdev;
static struct class *leds_cls;
static int led0,led1,led2,led3;
static int leds_drv_open(struct inode *inode, struct file *file)
{
printk(KERN_INFO"%s OK.\n",__func__);
return 0;
}
static ssize_t leds_drv_write(struct file *file, const char __user *user_buf, size_t count, loff_t * ppos)
{
int minor = iminor(file->f_inode);
char buf;
printk(KERN_INFO"%s OK.\n",__func__);
if(count != 1){
printk(KERN_INFO"write count != 1.\n");
return 1;
}
if (copy_from_user(&buf, user_buf, count))
return -EFAULT;
if(0x01 == buf)
{
switch(minor){
case 0:
gpio_set_value(led0, 0);
break;
case 1:
gpio_set_value(led1, 0);
break;
case 2:
gpio_set_value(led2, 0);
break;
case 3:
gpio_set_value(led3, 0);
break;
default:
printk(KERN_INFO"%s receive minor error.\n",__func__);
}
}
else if(0x00 == buf)
{
switch(minor){
case 0:
gpio_set_value(led0, 1);
break;
case 1:
gpio_set_value(led1, 1);
break;
case 2:
gpio_set_value(led2, 1);
break;
case 3:
gpio_set_value(led3, 1);
break;
default:
printk(KERN_INFO"%s receive minor error\n",__func__);
}
}
return 0;
}
static struct file_operations leds_fops = {
.owner = THIS_MODULE,
.open = leds_drv_open,
.write = leds_drv_write,
};
static int leds_probe(struct platform_device *pdev)
{
struct device *dev = &pdev->dev;
dev_t devid;
printk(KERN_INFO"%s OK.\n",__func__);
//1.申請裝置號
if(alloc_chrdev_region(&devid, 0, TI_LEDS_CNT, "ti_leds") < 0)
{
printk(KERN_INFO"%s ERROR.\n",__func__);
goto error;
}
major = MAJOR(devid);
//2.註冊到系統中
cdev_init(&leds_cdev, &leds_fops);
cdev_add(&leds_cdev, devid, TI_LEDS_CNT);
leds_cls = class_create(THIS_MODULE, "ti_leds");
device_create(leds_cls, NULL, MKDEV(major, 0), NULL, "ti_led0");
device_create(leds_cls, NULL, MKDEV(major, 1), NULL, "ti_led1");
device_create(leds_cls, NULL, MKDEV(major, 2), NULL, "ti_led2");
device_create(leds_cls, NULL, MKDEV(major, 3), NULL, "ti_led3");
//3.硬體相關
led0 = of_get_named_gpio(dev->of_node, "am437x,led_gpio0", 0);;
led1 = of_get_named_gpio(dev->of_node, "am437x,led_gpio1", 0);;
led2 = of_get_named_gpio(dev->of_node, "am437x,led_gpio2", 0);;
led3 = of_get_named_gpio(dev->of_node, "am437x,led_gpio3", 0);
//printk(KERN_INFO"led0 = %d\n",led0);
//printk(KERN_INFO"led1 = %d\n",led1);
//printk(KERN_INFO"led2 = %d\n",led2);
//printk(KERN_INFO"led3 = %d\n",led3);
devm_gpio_request_one(dev, led0, GPIOF_OUT_INIT_HIGH, "LED0");
devm_gpio_request_one(dev, led1, GPIOF_OUT_INIT_HIGH, "LED1");
devm_gpio_request_one(dev, led2, GPIOF_OUT_INIT_HIGH, "LED2");
devm_gpio_request_one(dev, led3, GPIOF_OUT_INIT_HIGH, "LED3");
error:
unregister_chrdev_region(MKDEV(major, 0), TI_LEDS_CNT);
return 0;
}
static int leds_remove(struct platform_device *pdev)
{
unsigned i;
printk(KERN_INFO"%s OK.\n",__func__);
for(i=0;i<TI_LEDS_CNT;i++)
{
device_destroy(leds_cls, MKDEV(major, i));
}
class_destroy(leds_cls);
cdev_del(&leds_cdev);
unregister_chrdev(major, "ti_leds");
return 0;
}
static const struct of_device_id of_gpio_leds_match[] = {
{ .compatible = "ti_leds", },
{},
};
static struct platform_driver leds_drv = {
.probe = leds_probe,
.remove = leds_remove,
.driver = {
.name = "ti_am437x_leds_platform",
.owner = THIS_MODULE,
.of_match_table = of_match_ptr(of_gpio_leds_match),
},
};
static int leds_drv_init(void)
{
printk(KERN_INFO"%s OK.\n",__func__);
return platform_driver_register(&leds_drv);
}
static void leds_drv_exit(void)
{
printk(KERN_INFO"%s OK.\n",__func__);
platform_driver_unregister(&leds_drv);
}
module_init(leds_drv_init);
module_exit(leds_drv_exit);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("hceng <[email protected]>");
MODULE_DESCRIPTION("TI am437x board leds drvice");
MODULE_ALIAS("platform:device tree:ti_leds");
MODULE_VERSION("V3.0");
測試程式同前面的一樣。
6.心得
在我理解到驅動=裸機+軟體框架的時候,我對之前的裸機也就沒那麼排斥了。
而且這個軟體框架,就現在來看,核心的那幾步像:申請裝置號、註冊裝置、建立類和建立節點這些都不變