【嵌入式Linux】Jetson nano GPIO应用 | 驱动开发 | 官方gpiolib、设备树与chip_driver
GPIO子系统
0.暴露给应用层
应用
$ echo 79 > /sys/class/gpio/export //导出79号gpio 引脚，使得可在应用层访问
$ echo out > /sys/class/gpio/gpio79/direction //设置 为输出
$ echo 1 > /sys/class/gpio/gpio79/value //输出高电平 开灯
$ echo 0 > /sys/class/gpio/gpio79/value //输出低电平， 关灯
$ cat /sys/kernel/debug/gpio //查询gpio状态(问题：发现找不到gpio文件)
$ echo 79 > unexport //取消导出（发现gpio79消失了)
解决调试目录为空的问题
原因 //debug需要的文件系统 debugfs没有挂载
在 /etc/fstab 的后面添加一行
debugfs /sys/kernel/debug debugfs defaults 0 0
调试信息
$ cat /sys/kernel/debug/gpio //查看gpio 当前配置情况（驱动暴露的调试信息）
$ cat /sys/kernel/debug/tegra_gpio //查看GPIO 寄存器内容(和芯片手册进行对应)
$ cat /sys/kernel/debug/tegra_pinctrl_reg //查看 pinctrl 寄存器内容
1.最简读写文件(在/SYS下)
设备树
sys_rw_led{ //对应生成 /sys/devices/sys_rw_led/led_gpio
compatible = "sys_rw_led";
led_gpio = <&gpio TEGRA_GPIO(J,7) GPIO_ACTIVE_HIGH>;
};
验证测试
$ cd sys_rw_led
$ make
$ cp led.ko /nfs/rootfs
$ cd ~/kernel-4.9
$ make dtbs
$ cp arch/arm64/boot/dts/tegra210-p3448-0000-p3449-0000-b00.dtb /tftpboot/
重启板子
$ insmod led.ko
$ cd /sys/devices/sys_rw_led
$ echo 0 > led_gpio //关灯
$ echo 1 > led_gpio //亮灯
编译文件
//Makefile
ifeq ($(KERNELRELEASE),)
KERNELDIR ?= ~/kernel-4.9
PWD := $(shell pwd)
all:
$(MAKE) -C $(KERNELDIR) M=$(PWD) modules
clean:
rm -rf *.o *~ core .depend .*.cmd *.ko *.mod.c .tmp_versions Module* modules* a.out *.bak
else
obj-m := led.o
endif
驱动
-
of_get_named_gpio_flags//获取设备树节点的属性gpio_is_valid//判断是否合法devm_gpio_request//申请使用gpio，并调用设置pinctrl
-
device_create_file //根据设备树节点属性，创建相应的属性文件 /sys/devices/sys_rw_led/led_gpio
- static struct device_attribute dev_attr_file //属性文件的描述
//led.c
#include 2.读写多个属性文件（在SYS下）
设备树
sys_rw_gpio{
compatible = "bbcen,sys_rw_gpio";
led_gpio = <&gpio TEGRA_GPIO(J,7) GPIO_ACTIVE_HIGH>; //40pin 丝印 12
smoke_sensor_gpio = <&gpio TEGRA_GPIO(S,5) GPIO_ACTIVE_HIGH>; //40pin 丝印 29
};
验证测试
$ cd sys_read_write
$ make
$ cp gpio.ko /nfs/rootfs
$ cd ~/kernel-4.9
$ make dtbs
$ cp arch/arm64/boot/dts/tegra210-p3448-0000-p3449-0000-b00.dtb /tftpboot/
重启板子
$ insmod gpio.ko
$ cd /sys/devices/sys_rw_gpio
$ echo 0 > led_gpio //关灯
$ echo 1 > led_gpio //亮灯
$ cat smoke_sensor_gpio //读管脚输入电平，默认读到0，用杜邦线，把它接到前面亮灯的管脚时，能成功读到1
编译文件
ifeq ($(KERNELRELEASE),)
KERNELDIR ?= ~/kernel-4.9
PWD := $(shell pwd)
all:
$(MAKE) -C $(KERNELDIR) M=$(PWD) modules
clean:
rm -rf *.o *~ core .depend .*.cmd *.ko *.mod.c .tmp_versions Module* modules* a.out *.bak
else
obj-m := gpio.o
endif
驱动
-
定义一个结构体指针，分配空间，指定内容
-
device_attribute gpio_attr[]
-
sysfs_create_file //for循环读取，和上面的数组配合实现读多个属性
#include 3.点多个灯(官方示例)
帮助文档
官方有驱动文件了，只需要参考帮助文档改设备树，make menuconfig对应选配，就能用了
//Documentation/devicetree/bindings/leds/leds-gpio.txt
设备树
//tegra210-p3448-0000-p3449-0000-b00.dts
yhai-gpio-led {
compatible = "gpio-leds";
led1 {
label = "led1";
gpios = <&gpio TEGRA_GPIO(J,7) GPIO_ACTIVE_HIGH>; //对应40pin 丝印 12脚 接第一个灯
default-state = "off";
};
led2 {
label = "led2";
gpios = <&gpio TEGRA_GPIO(Z,0) GPIO_ACTIVE_HIGH>; //对应40pin 丝印 31脚 接第二个灯
default-state = "off";
};
led3 {
label = "led3";
gpios = <&gpio TEGRA_GPIO(S,5) GPIO_ACTIVE_HIGH>; //对应40pin 丝印 29脚 接第三个灯
default-state = "off";
};
};
官方驱动
//见drivers/leds/leds-gpio.c
static const struct of_device_id of_gpio_leds_match[] = {
{ .compatible = "gpio-leds", },
{},
};
static struct platform_driver gpio_led_driver = {
.probe = gpio_led_probe,
.driver = {
.name = "leds-gpio",
.of_match_table = of_gpio_leds_match,
},
};
module_platform_driver(gpio_led_driver);
内核配置
$ cd ~/kernel-4.9
$ make menuconfig
Device Drivers --->
[*] LED Support --->
<*> LED Class Support
<*> LED Support for GPIO connected LEDs
验证测试
$ make dtbs
$ cp arch/arm64/boot/dts/tegra210-p3448-0000-p3449-0000-b00.dtb /tftpboot/
重启板子
# cd /sys/class/leds/
# echo 1 > led1/brightness //点亮第一个灯
# echo 0 > led1/brightness //灭第一个灯
# echo 1 > led2/brightness //点亮第二个灯
# echo 0 > led2/brightness //灭第二个灯
# echo 1 > led3/brightness //点亮第三个灯
# echo 0 > led3/brightness //灭第三个灯
4.GPIO库gpiolib（对上统一操作接口）
//源码 drivers/gpio/gpiolib.c: gpio子系统的核心实现，对外提供驱动API接口
EXPORT_SYMBOL_GPL(gpiod_get);
EXPORT_SYMBOL_GPL(gpiod_direction_output);
EXPORT_SYMBOL_GPL(gpiod_set_value);
//源码 drivers/gpio/gpiolib-sysfs.c
int gpiod_export(struct gpio_desc *desc, bool direction_may_change)
{
device_create_with_groups(&gpio_class, &gdev->dev,
MKDEV(0, 0), data, gpio_groups,
ioname ? ioname : "gpio%u", //创建 /sys/class/gpio/gpio79 文件夹
desc_to_gpio(desc));
}
static ssize_t export_store(struct class *class,
struct class_attribute *attr,
const char *buf, size_t len)
{
gpio_to_desc(gpio);
gpiod_request(desc, "sysfs"); //先申请（检测是否被占用)
gpiod_export(desc, true); //导出 生成 /sys/class/gpio/gpio79 文件夹（包括direction value等）
}
static struct class_attribute gpio_class_attrs[] = {
__ATTR(export, 0200, NULL, export_store), //写：关联属性文件的写回调函数(*store) echo 79 > /sys/class/gpio/export 时触发
__ATTR(unexport, 0200, NULL, unexport_store),
__ATTR_NULL,
};
static struct class gpio_class = {
.name = "gpio",
.owner = THIS_MODULE,
.class_attrs = gpio_class_attrs,
};
int gpiochip_sysfs_register(struct gpio_device *gdev)
{
//创建 /sys/class/gpio/gpiochip0 文件夹
device_create_with_groups(&gpio_class, parent,
MKDEV(0, 0),
chip, gpiochip_groups,
"gpiochip%d", chip->base);
}
static int __init gpiolib_sysfs_init(void)
{
struct gpio_device *gdev;
class_register(&gpio_class); //注册 生成 /sys/class/gpio 文件夹
gpiochip_sysfs_register(gdev);
}
postcore_initcall(gpiolib_sysfs_init); //声明 在内核启动时自动加载
5.GPIO设备树
//帮助文档 Documentation/devicetree/bindings/gpio/nvidia,tegra186-gpio.txt
//tegra210-soc-base.dtsi cpu的基本配置
//位置: public_sources\hardware\nvidia\soc\t210\kernel-dts\tegra210-soc\
gpio: gpio@6000d000 {//gpio子节点
compatible = "nvidia,tegra210-gpio", "nvidia,tegra124-gpio", "nvidia,tegra30-gpio";
reg = <0x0 0x6000d000 0x0 0x1000>; //前2个数表示起始地址(由父节点的#address-cells = <2> 决定)
//后2个数表示长度范围(由父节点的#size-cells = <2> 决定)
//域名(0:spi 1:ppi) + 中断索引(36) + 触发方式(高电平触发） Documentation/devicetree/bindings/interrupt-controller/arm,gic.txt
interrupts = < 0 32 0x04 //32: gpio编号 0x04:高电平触发中断
0 33 0x04
0 34 0x04
0 35 0x04
0 55 0x04
0 87 0x04
0 89 0x04
0 125 0x04>;
status = "disabled"; //声明 本节点是禁用状态
#gpio-cells = <2>; //声明 引用本节点，用 gpios 属性传参时 参数占2个单位
gpio-controller; //声明本节点 是 GPIO 控制器
#interrupt-cells = <2>;
interrupt-controller; //声明本节点 是 中断 控制器
gpio-ranges = <&pinmux 0 0 246>; //设置gpio number 与 pinctrl number的 映射，详见PinCtrl子系统
};
6.GPIO芯片驱动gpio_chip_driver
( 由原厂开发)
//查看驱动信息
$ cat /proc/devices //查看内核加载的驱动设备
254 gpiochip
$ cat /sys/class/gpio/gpiochip0/label //查看驱动设备的标签名
tegra-gpio //对应 gpio-tegra.c 的 tgi->gc.label = "tegra-gpio";
//源码 gpio-tegra.c 英伟达原厂开发的芯片驱动
定义类
//gpio-tegra.c
struct tegra_gpio_info { //定义gpio类
struct device *dev;
void __iomem *regs;
struct irq_domain *irq_domain;
struct tegra_gpio_bank *bank_info;
const struct tegra_gpio_soc_config *soc;
struct gpio_chip gc; //gpio控制器
struct irq_chip ic; //irq控制器
u32 bank_count;
};
static struct tegra_gpio_info *gpio_info; //定义 gpio对象
static const struct of_device_id tegra_gpio_of_match[] = {
{ .compatible = "nvidia,tegra210-gpio", .data = &tegra210_gpio_config },
};
static struct platform_driver tegra_gpio_driver = {
.driver = {
.name = "tegra-gpio",
.of_match_table = tegra_gpio_of_match,
},
.probe = tegra_gpio_probe,
};
static int __init tegra_gpio_init(void)
{
return platform_driver_register(&tegra_gpio_driver);
}
subsys_initcall(tegra_gpio_init); //添加到内核启动列表中
构建对象（注册制）
- devm_kzalloc会自动释放资源，常用
static int tegra_gpio_probe(struct platform_device *pdev)
{
struct tegra_gpio_info *tgi; //定义对象
//为对象分配空间
tgi = devm_kzalloc(&pdev->dev, sizeof(*tgi), GFP_KERNEL);
if (!tgi)
return -ENODEV;
gpio_info = tgi;
//获取所有bank的中断资源
for (;;) {
res = platform_get_resource(pdev, IORESOURCE_IRQ, //见设备树 interrupts =< 0 32 0x04 ...>
tgi->bank_count);
if (!res)
break;
tgi->bank_count++;
}
//初始化对象：里面的变量都赋值，指针都指向实体，
tgi->gc.label = "tegra-gpio"; //对应 /sys/class/gpio/gpiochip0/label
tgi->gc.request = tegra_gpio_request; //申请gpio(如果被占用，将申请失败)
tgi->gc.free = tegra_gpio_free; //释放gpio(释放后，别的驱动才能申请)
tgi->gc.direction_input = tegra_gpio_direction_input; //
tgi->gc.get = tegra_gpio_get;
tgi->gc.direction_output = tegra_gpio_direction_output;//gpio 方向设为输出
tgi->gc.set = tegra_gpio_set;
//获取MEM资源
res = platform_get_resource(pdev, IORESOURCE_MEM, 0); //见设备树 reg = <0x0 0x6000d000 0x0 0x1000>;
tgi->regs = devm_ioremap_resource(&pdev->dev, res);
if (IS_ERR(tgi->regs))
return PTR_ERR(tgi->regs);
tegra_gpio_debuginit(tgi); //添加 调试功能
}
static inline void tegra_gpio_writel(struct tegra_gpio_info *tgi,
u32 val, u32 reg)
{
__raw_writel(val, tgi->regs + reg); /* 实现见 arch/arm64/include/asm/io.h
用C语言中嵌入汇编方式 ,用str 汇编指令 实现写数据
static inline void __raw_writel(u32 val, volatile void __iomem *addr)
{
asm volatile("str %w0, [%1]" : : "rZ" (val), "r" (addr));
}
*/
}
static void tegra_gpio_mask_write(struct tegra_gpio_info *tgi, u32 reg,
int gpio, int value)
{
tegra_gpio_writel(tgi, val, reg);
}
static void tegra_gpio_set(struct gpio_chip *chip, unsigned offset, int value)
{
//通过 GPIO_MSK_OUT 宏 实现各gpio 地址间转换关系(如不同端口 偏移量)
tegra_gpio_mask_write(tgi, GPIO_MSK_OUT(tgi, offset), offset, value);
}
static int tegra_gpio_direction_output(struct gpio_chip *chip, unsigned offset,
int value)
{
struct tegra_gpio_info *tgi = gpiochip_get_data(chip);
int ret;
tegra_gpio_set(chip, offset, value);
tegra_gpio_mask_write(tgi, GPIO_MSK_OE(tgi, offset), offset, 1);
tegra_gpio_enable(tgi, offset);
ret = pinctrl_gpio_direction_output(chip->base + offset); //向pinctrl子系统 申请管脚 设为gpio输出模式
return ret;
}
支持SYS控制
#ifdef CONFIG_DEBUG_FS //当打开 内核调试关，才把调试源码编译进来
#include 寄存器自适应(管脚变了，不用再该代码，只需该改备树)
#include