1. 内核中断的处理过程和实现原理
依照原理图，将中断注册进内核的步骤为：
- 获取中断在 irq_desc 数组中的位置（软中断号）
- 定义中断处理函数
- 申请一个 irqaction 空间，将中断处理相关的信息保存在这个空间
- 将 irqaction 看似首地址保存至这个中断的 irq_desc 空间中
2. 内核中断子系统相关 API
- 解析中断相关的设备树节点：通过名字、路径或者 conpatible，参考 GPIO 子系统笔记
- 解析设备树节点获取当前设备对应中断的软中断号
int irq_of_parse_and_map(struct device_node *node, int index) 功能: 对当前设备进行分析并且映射出当前中断的软中断号 参数: node: 设备树节点结构体指针 index: 索引号 返回值: 成功返回软中断号，失败返回 0
- 注册中断
int request_irq(unsigned int irq, irq_handler_t handler, unsigned long flags, const char *name, void *dev) 功能: 注册中断 参数: irq: 软中断 handler: 中断处理函数的函数指针 typedef irqreturn_t (*irq_handler_t)(int , void *); 中断处理函数的返回值: IRQ_NONE 不是这个设备的中断，没有被处理 IRQ_HANDLED 中断被正常处理 IRQ_WAKE_THREAD 唤醒一个处理线程去处理中断 flags: 用于设置中断的触发方式 IRQF_TRIGGER_RISING 上升沿触发 IRQF_TRIGGER_FALLING 下降沿触发 IRQF_TRIGGER_HIGH 高电平触发 IRQF_TRIGGER_LOW 低电平触发 IRQF_SHARED 设置当前中断为共享中断 name: 中断名 dev: 传递进入中断处理函数的参数 返回值: 成功返回 0，失败返回错误码
3. 按键中断的设备树编写
3.1 按键中断的硬件原理图
在
stm32mp157a.dtsi 文件中以及有 gic\exti\gpio 的设备树节点的封装了，需要我们做的是添加按键的设备树节点，并且和 gpiof 在中断层次上实现关联。3.2 中断处理相关的设备树节点
GPIOF
//定义位置：stm32mp151.dtsi pinctrl: pin-controller@50002000 { interrupt-parent = <&exti>;//指定当前节点的中断父节点为exti gpiof: gpio@50007000 { //一个空属性，将节点声明为接收中断信号的设备 interrupt-controller; //其他节点引用此节点作为中断控制节点是用于描述的u32的个数 #interrupt-cells = <2>; reg = <0x5000 0x400>; clocks = <&rcc GPIOF>; st,bank-name = "GPIOF"; status = "disabled"; }; }; //引用位置：stm32mp15xxac-pinctrl.dtsi &pinctrl { gpiof: gpio@50007000 { status = "okay"; ngpios = <16>; gpio-ranges = <&pinctrl 0 80 16>; }; };
EXTI
soc { compatible = "simple-bus"; #address-cells = <1>; #size-cells = <1>; interrupt-parent = <&intc>;//当前节点的中断父节点时intc ranges; exti: interrupt-controller@5000d000 { compatible = "st,stm32mp1-exti", "syscon"; interrupt-controller;//声明当前节点是一个中断控制节点 //引用此节点作为中断控制时需要用2个u32进行描述 #interrupt-cells = <2>; reg = <0x5000d000 0x400>; }; };
GIC
intc: interrupt-controller@a0021000 { compatible = "arm,cortex-a7-gic"; #interrupt-cells = <3>; interrupt-controller;//声明当前节点是一个中断控制节点 reg = <0xa0021000 0x1000>, <0xa0022000 0x2000>; };
3.3 添加按键的设备树节点
查看 Linux 官方设备树中断手册：Device Tree Usage - eLinux.org
四个属性用于描述中断连接：
interrupt-controller：一个空属性，将节点声明为接收中断信号的设备
#interrupt-cells：用于声明引用此节点作为中断控制器节点时使用的u32的个数
interrupt-parent：设备节点的属性，其中包含它所附加到的中断控制器的句柄。没有中断父属性的节点也可以从其父节点继承该属性。
interrupts：设备节点的属性，包含中断说明符列表，设备上的每个中断输出信号对应一个
进入内核顶层目录
/Documentation/devicetree/bindings/interrupt-controller文档相关内容节选
Nodes that describe devices which generate interrupts must contain an
"interrupts" property, an "interrupts-extended" property, or both. If both are
present, the latter should take precedence; the former may be provided simply
for compatibility with software that does not recognize the latter. These
properties contain a list of interrupt specifiers,
Example:
interrupt-parent = <&intc1>;
interrupts = <5 0>, <6 0>;
The "interrupt-parent" property is used to specify the controller to which
interrupts are routed and contains a single phandle referring to the interrupt
controller node.
Interrupts listed in the
"interrupts" property are always in reference to the node's interrupt parent.
The "interrupts-extended" property is a special form; useful when a node needs
to reference multiple interrupt parents or a different interrupt parent than
the inherited one.
Example:
interrupts-extended = <&intc1 5 1>, <&intc2 1 0>;
2) Interrupt controller nodes
A device is marked as an interrupt controller with the "interrupt-controller"
property. This is a empty, boolean property. An additional "#interrupt-cells"
property defines the number of cells needed to specify a single interrupt.
two cells
…
The #interrupt-cells property is set to 2 and the first cell defines the
index of the interrupt within the controller, while the second cell is used
to specify any of the following flags:
- bits[3:0] trigger type and level flags
1 = low-to-high edge triggered
2 = high-to-low edge triggered
4 = active high level-sensitive
8 = active low level-sensitive
添加按键的设备树节点：
mykeys{ interrupt-parent=<&gpiof>; //9表示引用中断父节点时的索引信息 0表示默认设置 interrupts=<9 0>,<7 0>,<8 0>; }; //或者 mykeys{ interrupts-extended = <&gpiof 9 0>, <&gpiof 7 0>, <&gpiof 8 0>; };
