1.1 GPIO驱动开发

GPIO 介绍

GPIO 是 General Purpose Input Output（通用输入/输出） 的缩写，也就意味着这种类型的外设可以配置为多种输入/输出类型。单根GPIO的模型可以简单理解为一根导线。导线的一端留给硬件工程师，他们可以将这一端任意的连接到他们想要的地方，然后告诉驱动工程师，他们想要 ”这根线“ 起到什么作用；导线的一端连接到cpu核心，驱动工程师通过cpu配置这个模块为指定的功能。

一般来说，GPIO可以用于获取某个的高低电平，作为cpu中断触发源等等。下面的两个实验将分别验证gpio的 irq 和输出工作原理。

memory mapped io

关于这个的实现原理，本章不做过多的解释，否则篇幅将会过长。简单的来说，有了这个技术之后，外设对于cpu来说就是为一块物理内存，cpu可以像操作内存一样来操作设备。在没有这个技术之前，一些古老的设备，像intel的16位cpu，必须使用in/out一些特殊的端口来访问外设。

qemu平台关机实验

对于一些简单的设备，qemu能够很好的进行模拟。因此，对于部分没有开发板而想尝试进行驱动开发学习的同学，我们提供了基于qemu的部分实验。

实验原理

gpio 模块介绍

本次实验使用的gpio模块为pl061, 它是arm提供的一个集成化的gpio模块，具有8个引脚，具备常见的gpio功能, qemu也能对这个设备进行模拟（可以使用 qemu-system-aarch64 --device help 来查看qemu支持的设备）。
pl061 相关寄存器介绍（注意：不同的外设有不同的寄存器，对于驱动工程师来说，阅读外设datasheet是必不可少的技能。所以建议暂时先跳过本节，阅读后再来验证自己的想法）
- GPIOIS 和 GPIOIEV
  
  这两个寄存器的宽度都为为8bit，对应8个引脚。这两个寄存器共同决定了某个引脚的中断触发方法。他们按如下的方式决定中断类型。
  
  GPIOIS_i GPIOEV_i 引脚i中断方式
  
  0 0 下降沿触发
  
  0 1 上升沿触发
  
  1 0 低电平触发
  
  1 1 高电平触发
GPIOIE

全称是 PrimeCell GPIO interrupt enable register，翻译过来就是中断使能寄存器。宽度为8bit，对应8个引脚。每一个bit用来配置对应引脚的是否使能中断，1是使能，0是不使能。

GPIOIS_i	GPIOEV_i	引脚i中断方式
0	0	下降沿触发
0	1	上升沿触发
1	0	低电平触发
1	1	高电平触发

实验过程

在arceos代码仓库下，使用example为helloworld，先尝试运行得到以下结果。

运行结果

arceos git:(main)✗ make A=examples/helloworld PLATFORM=aarch64-qemu-virt ARCH=aarch64 LOG=debug FEATURES="driver-ramdisk,irq" run ACCEL=n GRAPHIC=n

  ... # skip part build log
  axconfig-gen configs/defconfig.toml configs/platforms/aarch64-qemu-virt.toml  -w smp=1 -w arch=aarch64 -w platform=aarch64-qemu-virt -o "/Users/jp/code/arceos/.axconfig.toml" -c "/Users/jp/code/arceos/.axconfig.toml"
  Building App: helloworld, Arch: aarch64, Platform: aarch64-qemu-virt, App type: rust
  cargo -C examples/helloworld build -Z unstable-options --target aarch64-unknown-none-softfloat --target-dir /Users/jp/code/arceos/target --release  --features "axstd/log-level-debug axstd/driver-ramdisk axstd/irq"
  Finished `release` profile [optimized] target(s) in 0.08s
  rust-objcopy --binary-architecture=aarch64 examples/helloworld/helloworld_aarch64-qemu-virt.elf --strip-all -O binary examples/helloworld/helloworld_aarch64-qemu-virt.bin
  Running on qemu...
  qemu-system-aarch64 -m 128M -smp 1 -cpu cortex-a72 -machine virt -kernel examples/helloworld/helloworld_aarch64-qemu-virt.bin -nographic

      d8888                            .d88888b.   .d8888b.
      d88888                           d88P" "Y88b d88P  Y88b
      d88P888                           888     888 Y88b.
  d88P 888 888d888  .d8888b  .d88b.  888     888  "Y888b.
  d88P  888 888P"   d88P"    d8P  Y8b 888     888     "Y88b.
  d88P   888 888     888      88888888 888     888       "888
  d8888888888 888     Y88b.    Y8b.     Y88b. .d88P Y88b  d88P
  d88P     888 888      "Y8888P  "Y8888   "Y88888P"   "Y8888P"

  arch = aarch64
  platform = aarch64-qemu-virt
  target = aarch64-unknown-none-softfloat
  build_mode = release
  log_level = debug
  smp = 1

  [  0.001902 0 axruntime:130] Logging is enabled.
  [  0.002488 0 axruntime:131] Primary CPU 0 started, dtb = 0x44000000.
  [  0.002738 0 axruntime:133] Found physcial memory regions:
  [  0.002968 0 axruntime:135]   [PA:0x40200000, PA:0x40206000) .text (READ | EXECUTE | RESERVED)
  [  0.003304 0 axruntime:135]   [PA:0x40206000, PA:0x40209000) .rodata (READ | RESERVED)
  [  0.003502 0 axruntime:135]   [PA:0x40209000, PA:0x4020d000) .data .tdata .tbss .percpu (READ | WRITE | RESERVED)
  [  0.003714 0 axruntime:135]   [PA:0x4020d000, PA:0x4024d000) boot stack (READ | WRITE | RESERVED)
  [  0.003892 0 axruntime:135]   [PA:0x4024d000, PA:0x40250000) .bss (READ | WRITE | RESERVED)
  [  0.004080 0 axruntime:135]   [PA:0x40250000, PA:0x48000000) free memory (READ | WRITE | FREE)
  [  0.004290 0 axruntime:135]   [PA:0x9000000, PA:0x9001000) mmio (READ | WRITE | DEVICE | RESERVED)
  [  0.004482 0 axruntime:135]   [PA:0x9100000, PA:0x9101000) mmio (READ | WRITE | DEVICE | RESERVED)
  [  0.004662 0 axruntime:135]   [PA:0x8000000, PA:0x8020000) mmio (READ | WRITE | DEVICE | RESERVED)
  [  0.004806 0 axruntime:135]   [PA:0xa000000, PA:0xa004000) mmio (READ | WRITE | DEVICE | RESERVED)
  [  0.004948 0 axruntime:135]   [PA:0x10000000, PA:0x3eff0000) mmio (READ | WRITE | DEVICE | RESERVED)
  [  0.005098 0 axruntime:135]   [PA:0x4010000000, PA:0x4020000000) mmio (READ | WRITE | DEVICE | RESERVED)
  [  0.005284 0 axruntime:150] Initialize platform devices...
  [  0.005420 0 axhal::platform::aarch64_common::gic:51] Initialize GICv2...
  [  0.006258 0 axruntime:176] Initialize interrupt handlers...
  [  0.006466 0 axhal::irq:32] irq=30 enabled
  [  0.006830 0 axruntime:188] Primary CPU 0 init OK.
  Hello, world!
  [  0.007086 0 axruntime:201] main task exited: exit_code=0
  [  0.007248 0 axhal::platform::aarch64_common::psci:98] Shutting down...

由于目前arceos是unikernel模式，特权级为el1，所以可以直接在 main.c 中操作设备地址（需要注意的是，这不是一种正确的做法。但对于初学者，为了不在一开始就去研究arecos的复杂代码框架，可以短暂的把实现代码写在这儿。），将pl061模块的三号引脚配置为irq模式。

#![allow(unused)]
fn main() {
// examples/helloworld/main.c
...
/// 0x9030000 是 qemu模拟的aarch64-qemu-virt机器的 pl061模块的基地址(物理地址)。
/// irq number 39 从 aarch64-qemu-virt机器的设备树中找到，7 + 外部中断base(32) = 39
unsafe fn set_gpio_irq_enable() {
    // PHYS_VIRT_OFFSET 是 arceos 初始化时，将物理内存映射时进行的偏移。
    let base_addr = (0x9030000 + PHYS_VIRT_OFFSET) as *mut u8;
    // pl061的3号引脚
    let pin = 3;
    // 将interrupt设置为边缘触发
    let gpio_is = base_addr.add(0x404);
    *gpio_is = *gpio_is & !(1 << pin);
    // 设置触发事件
    let gpio_iev = base_addr.add(0x40c);
    *gpio_iev = *gpio_iev & !(1 << pin);
    
    // 设置中断使能
    let gpio_ie = base_addr.add(0x410);
    *gpio_ie = 0;
    *gpio_ie = *gpio_ie | (1 << pin);

    fn shut_down() {
       println!("shutdown function called");
       unsafe {
           let base_addr = (0x9030000 + PHYS_VIRT_OFFSET) as *mut u8;
           let pin = 3;
           // clear interrupt
           let gpio_ic = base_addr.add(0x41c);
           *gpio_ic = (1 << pin);
           // 关机命令
           core::arch::asm!(
               "mov w0, #0x18;
               hlt #0xf000"
           )
       }
    };
    register_handler(39, shut_down);
    println!("set irq done");
}
}

并将中断号注册到 GIC(generic interrupt controller)中，中断号是39。

#![allow(unused)]
fn main() {
// examples/helloworld/main.c
...
/// 0x9030000 是 qemu模拟的aarch64-qemu-virt机器的 pl061模块的基地址(物理地址)。
/// irq number 39 从 aarch64-qemu-virt机器的设备树中找到，7 + 外部中断base(32) = 39
unsafe fn set_gpio_irq_enable() {
   // PHYS_VIRT_OFFSET 是 arceos 初始化时，将物理内存映射时进行的偏移。
let base_addr = (0x9030000 + PHYS_VIRT_OFFSET) as *mut u8;
// pl061的3号引脚
let pin = 3;
// 将interrupt设置为边缘触发
let gpio_is = base_addr.add(0x404);
*gpio_is = *gpio_is & !(1 << pin);
// 设置触发事件
let gpio_iev = base_addr.add(0x40c);
*gpio_iev = *gpio_iev & !(1 << pin);

// 设置中断使能
let gpio_ie = base_addr.add(0x410);
*gpio_ie = 0;
*gpio_ie = *gpio_ie | (1 << pin);

    fn shut_down() {
        println!("shutdown function called");
        unsafe {
            let base_addr = (0x9030000 + PHYS_VIRT_OFFSET) as *mut u8;
            let pin = 3;
            // clear interrupt
            let gpio_ic = base_addr.add(0x41c);
            *gpio_ic = (1 << pin);
            // 关机命令，可以用别的函数替代
            core::arch::asm!(
                "mov w0, #0x18;
                hlt #0xf000"
            )
        }
    };
    // register handler 会同时将注册和在gic中使能中断完成。
    register_handler(39, shut_down);
    println!("set irq done");
}
}

在main中死循环，等待gpio触发中断。

#[cfg_attr(feature = "axstd", unsafe(no_mangle))]
fn main() {
  println!("Hello, world!");
  unsafe {
      set_gpio_irq_enable();
  }
  println!("loop started!");
  loop {
      sleep(time::Duration::from_millis(10));
  }
}

重新执行第一步命令，若无报错，输入 ctrl + a + c 进入qemu的console模式，输入system_powerdown时，qemu会模拟一次中断。

...
  [  0.005842 0 axhal::platform::aarch64_common::gic:51] Initialize GICv2...
  [  0.006358 0 axruntime:176] Initialize interrupt handlers...
  [  0.006554 0 axhal::irq:32] irq=30 enabled
  [  0.007232 0 axruntime:188] Primary CPU 0 init OK.
  Hello, world!
  GPIORIS=0x0
  [  0.007688 0 axhal::irq:32] irq=39 enabled
  set irq done
  loop started!
  QEMU 9.2.0 monitor - type 'help' for more information
  (qemu) syst
  system_powerdown  system_reset      system_wakeup     
  (qemu) system_powerdown

GIC 会将中断分发给 arm 某个核心（由于我们是单核，不存在分发）, cpu对我们注册的关机函数进行回调。

  ...
  (qemu) system_powerdown 
  (qemu) shutdown function called
  [ 50.194414 0 axruntime::lang_items:5] panicked at /Users/jp/.cargo/registry/src/mirrors.ustc.edu.cn-38d0e5eb5da2abae/axcpu-0.1.0/src/aarch64/trap.rs:112:13:
  Unhandled synchronous exception @ 0xffff0000402010b0: ESR=0x2000000 (EC 0b000000, ISS 0x0)
  [ 50.195002 0 axhal::platform::aarch64_common::psci:98] Shutting down...

飞腾派点灯实验

实验原理

基本思想是将GPIO配置为作为输出模式，对应的，这个GPIO可以输出为高电平或者低电平。我们都学过初中物理，知道当一个led灯两侧有足够的电压和电流的时候，它就会亮。不过一般的GPIO线输出电流能力都不强，不足以驱动一个led灯。所以一般会用以下两种方式来实现：

led正极接电源，负极接gpio。gpio输出为低时，led点亮。
led接 mos 管的gate。一般来说，GPIO为高电压时，会使得mos管闭合，led点亮；反之则熄灭。

参照飞腾派的硬件原理图，板子上有一个灯可以被我们控制，也就是led20，控制方法为第二种方法，控制GPIO线为GPIO1_8。 cpu_run gpio1_8

当然，如果你愿意，飞腾派开发板提供了很多GPIO的拓展线。你可以自己实现一套电路来点亮外接的led灯。

我们最终要实现led灯的"心跳"效果，即亮1秒，暗1秒，如此往复循环。

寄存器定义

notice：飞腾派上的GPIO模块操作方式都是统一的，唯一的区别是有的gpio需要先进行引脚复用的配置。具体操作可以参照参考飞腾派裸机开发手册进行配置。本次使用的引脚不需要配置，因为笔者没有找到这个GPIO的引脚复用配置寄存器。按照官方文档描述，没有找到就是不需要配置，所以可以认为这个引脚只有gpio功能。

对于输入输出，我们只关心以下三个寄存器，他们的定义可以在飞腾派软件开发手册很轻松的找到（而且是中文～），这里就不做复制粘贴的工作了。

GPIO_SWPORT_DR (0x00)
GPIO_SWPORT_DDR (0x04)
GPIO_EXT_PORT (0x08)

实验过程

编写驱动代码，实现 set_dir 和 set_data 操作，示例代码如下：

#![allow(unused)]
fn main() {
use bitflags::bitflags;
use safe_mmio::fields::ReadWrite;
use zerocopy::{FromBytes, Immutable, IntoBytes, KnownLayout};

#[derive(Clone, Eq, FromBytes, Immutable, IntoBytes, KnownLayout, PartialEq)]
#[repr(C, align(4))]
pub struct PhitiumGpio {
  data: ReadWrite<GpioPins>,
  resv: ReadWrite<u16>,
  dir: ReadWrite<GpioPins>,
  resv2: ReadWrite<u16>,
}

#[repr(transparent)]
#[derive(Copy, Clone, Debug, Eq, FromBytes, Immutable, IntoBytes, KnownLayout, PartialEq)]
pub struct GpioPins(u16);

bitflags! {
  impl GpioPins: u16 {
      const p0 = 1<<0;
      const p1 = 1<<1;
      const p2 = 1<<2;
      const p3 = 1<<3;
      const p4 = 1<<4;
      const p5 = 1<<5;
      const p6 = 1<<6;
      const p7 = 1<<7;
      const p8 = 1<<8;
      const p9 = 1<<9;
      const p10 = 1<<10;
      const p11 = 1<<11;
      const p12 = 1<<12;
      const p13 = 1<<13;
      const p14 = 1<<14;
      const p15 = 1<<15;
  }
}

impl PhitiumGpio {
  pub fn new(base: usize) -> &'static mut Self {
      let b = base as *mut PhitiumGpio;
      unsafe { &mut (*b) }
  }
  pub fn set_pin_dir(&mut self, pin: GpioPins, dir: bool) {
      let mut status = self.dir.0.bits();
      debug!("dir data = {status}");
      let pb = pin.bits();
      if dir == true {
          status |= pb;
      } else {
          status &= !pb;
      }
      debug!("dir data = {status}");
      self.dir.0 = (GpioPins::from_bits_truncate(status));
  }
  pub fn set_pin_data(&mut self, pin: GpioPins, data: bool) {
      let mut status = self.dir.0.bits();
      debug!(" data = {status}");
      let pb = pin.bits();
      if data == true {
          status |= pb;
      } else {
          status &= !pb;
      }
      debug!(" data = {status}");
      self.data.0 = (GpioPins::from_bits_truncate(status));
  }
}
pub use crate::mem::phys_to_virt;
pub use memory_addr::PhysAddr;

pub const BASE1: PhysAddr = pa!(0x28035000);
}

由于我们目前暂时没有文件系统，无法通过读写文件的方式来控制GPIO。这里直接在main.rs中实例一个GPIO控制器进行相关初始化。

// examples/helloworld/src/main.rs

#![cfg_attr(feature = "axstd", no_std)]
#![cfg_attr(feature = "axstd", no_main)]

use core::time;

#[cfg(feature = "axstd")]
use axstd::println;

use axstd::thread::sleep;

#[cfg_attr(feature = "axstd", unsafe(no_mangle))]
fn main() {
    println!("Hello, world!");
    let gpio0 = axhal::platform::gpio::PhitiumGpio::new(
        axhal::platform::gpio::phys_to_virt(axhal::platform::gpio::BASE1).into(),
    );
    let p = axhal::platform::gpio::GpioPins::p8;
    gpio0.set_pin_dir(p, true);
    let mut data = false;
    loop {
       sleep(time::Duration::from_secs(1));
       gpio0.set_pin_data(p, data);
       println!("current data: {data}");
       data = !data;
    }
}

创建一个大loop，在这个loop中，我们不停的将pin 8的值进行反转，反转一次，sleep 1s，这样就实现了1s灭，1s亮的效果。

  // examples/helloworld/src/main.rs

  #![cfg_attr(feature = "axstd", no_std)]
  #![cfg_attr(feature = "axstd", no_main)]

  use core::time;

  #[cfg(feature = "axstd")]
  use axstd::println;

  use axstd::thread::sleep;

  #[cfg_attr(feature = "axstd", unsafe(no_mangle))]
  fn main() {
      println!("Hello, world!");
      let gpio0 = axhal::platform::gpio::PhitiumGpio::new(
         axhal::platform::gpio::phys_to_virt(axhal::platform::gpio::BASE1).into(),
      );
      let p = axhal::platform::gpio::GpioPins::p8;
      gpio0.set_pin_dir(p, true);
      et mut data = false;
      loop {
          sleep(time::Duration::from_secs(1));
          gpio0.set_pin_data(p, data);
          println!("current data: {data}");
          data = !data;
      }
 }

通过make A=examples/helloworld ARCH=aarch64 PLATFORM=aarch64-phytium-pi FEATURES=irq LOG=debug进行编译，并烧入飞腾派运行。下面是运行日志以及实拍。

运行结果

Starting kernel ...


      d8888                            .d88888b.   .d8888b.
      d88888                           d88P" "Y88b d88P  Y88b
    d88P888                           888     888 Y88b.
    d88P 888 888d888  .d8888b  .d88b.  888     888  "Y888b.
  d88P  888 888P"   d88P"    d8P  Y8b 888     888     "Y88b.
  d88P   888 888     888      88888888 888     888       "888
d8888888888 888     Y88b.    Y8b.     Y88b. .d88P Y88b  d88P
d88P     888 888      "Y8888P  "Y8888   "Y88888P"   "Y8888P"

arch = aarch64
platform = aarch64-phytium-pi
target = aarch64-unknown-none-softfloat
build_mode = release
log_level = trace
smp = 1

[ 13.461312 0 axruntime:130] Logging is enabled.
[ 13.467040 0 axruntime:131] Primary CPU 0 started, dtb = 0xf9c29000.
[ 13.474591 0 axruntime:133] Found physcial memory regions:
[ 13.481276 0 axruntime:135]   [PA:0x90000000, PA:0x90007000) .text (READ | EXECUTE | RESERVED)
[ 13.491083 0 axruntime:135]   [PA:0x90007000, PA:0x9000a000) .rodata (READ | RESERVED)
[ 13.500197 0 axruntime:135]   [PA:0x9000a000, PA:0x9000e000) .data .tdata .tbss .percpu (READ | WRITE | RESERVED)
[ 13.511655 0 axruntime:135]   [PA:0x9000e000, PA:0x9004e000) boot stack (READ | WRITE | RESERVED)
[ 13.521724 0 axruntime:135]   [PA:0x9004e000, PA:0x90051000) .bss (READ | WRITE | RESERVED)
[ 13.531272 0 axruntime:135]   [PA:0x90051000, PA:0x100000000) free memory (READ | WRITE | FREE)
[ 13.541167 0 axruntime:135]   [PA:0x2800c000, PA:0x2800d000) mmio (READ | WRITE | DEVICE | RESERVED)
[ 13.551496 0 axruntime:135]   [PA:0x2800d000, PA:0x2800e000) mmio (READ | WRITE | DEVICE | RESERVED)
[ 13.561825 0 axruntime:135]   [PA:0x2800e000, PA:0x2800f000) mmio (READ | WRITE | DEVICE | RESERVED)
[ 13.572155 0 axruntime:135]   [PA:0x2800f000, PA:0x28010000) mmio (READ | WRITE | DEVICE | RESERVED)
[ 13.582484 0 axruntime:135]   [PA:0x30000000, PA:0x38000000) mmio (READ | WRITE | DEVICE | RESERVED)
[ 13.592813 0 axruntime:135]   [PA:0x40000000, PA:0x50000000) mmio (READ | WRITE | DEVICE | RESERVED)
[ 13.603142 0 axruntime:135]   [PA:0x58000000, PA:0x80000000) mmio (READ | WRITE | DEVICE | RESERVED)
[ 13.613471 0 axruntime:135]   [PA:0x28014000, PA:0x28016000) mmio (READ | WRITE | DEVICE | RESERVED)
[ 13.623800 0 axruntime:135]   [PA:0x28016000, PA:0x28018000) mmio (READ | WRITE | DEVICE | RESERVED)
[ 13.634130 0 axruntime:135]   [PA:0x28018000, PA:0x2801a000) mmio (READ | WRITE | DEVICE | RESERVED)
[ 13.644459 0 axruntime:135]   [PA:0x2801a000, PA:0x2801c000) mmio (READ | WRITE | DEVICE | RESERVED)
[ 13.654788 0 axruntime:135]   [PA:0x2801c000, PA:0x2801e000) mmio (READ | WRITE | DEVICE | RESERVED)
[ 13.665117 0 axruntime:135]   [PA:0x28034000, PA:0x28035000) mmio (READ | WRITE | DEVICE | RESERVED)
[ 13.675446 0 axruntime:135]   [PA:0x28035000, PA:0x28036000) mmio (READ | WRITE | DEVICE | RESERVED)
[ 13.685776 0 axruntime:135]   [PA:0x28036000, PA:0x28037000) mmio (READ | WRITE | DEVICE | RESERVED)
[ 13.696105 0 axruntime:135]   [PA:0x28037000, PA:0x28038000) mmio (READ | WRITE | DEVICE | RESERVED)
[ 13.706434 0 axruntime:135]   [PA:0x28038000, PA:0x28039000) mmio (READ | WRITE | DEVICE | RESERVED)
[ 13.716763 0 axruntime:135]   [PA:0x28039000, PA:0x2803a000) mmio (READ | WRITE | DEVICE | RESERVED)
[ 13.727093 0 axruntime:150] Initialize platform devices...
[ 13.733776 0 axhal::platform::aarch64_common::gic:51] Initialize GICv2...
[ 13.741897 0 axhal::platform::aarch64_common::gic:27] GICD set enable: 30 true
[ 13.750182 0 axhal::platform::aarch64_common::gic:27] GICD set enable: 116 true
[ 13.758688 0 axruntime:176] Initialize interrupt handlers...
[ 13.765545 0 axhal::platform::aarch64_common::gic:36] register handler irq 30
[ 13.773878 0 axhal::platform::aarch64_common::gic:27] GICD set enable: 30 true
[ 13.782298 0 axruntime:188] Primary CPU 0 init OK.
Hello, world!
[ 13.789589 0 axhal::platform::aarch64_phytium_pi::gpio:46] dir data = 0
[ 13.797401 0 axhal::platform::aarch64_phytium_pi::gpio:53] dir data = 256
[ 14.805386 0 axhal::platform::aarch64_phytium_pi::gpio:58]  data = 256
[ 14.810239 0 axhal::platform::aarch64_phytium_pi::gpio:65]  data = 0
current data: false
[ 15.819614 0 axhal::platform::aarch64_phytium_pi::gpio:58]  data = 256
[ 15.824467 0 axhal::platform::aarch64_phytium_pi::gpio:65]  data = 256
current data: true
[ 16.833928 0 axhal::platform::aarch64_phytium_pi::gpio:58]  data = 256
[ 16.838781 0 axhal::platform::aarch64_phytium_pi::gpio:65]  data = 0
current data: false
[ 17.848156 0 axhal::platform::aarch64_phytium_pi::gpio:58]  data = 256
[ 17.853009 0 axhal::platform::aarch64_phytium_pi::gpio:65]  data = 256
current data: true
[ 18.862470 0 axhal::platform::aarch64_phytium_pi::gpio:58]  data = 256
[ 18.867323 0 axhal::platform::aarch64_phytium_pi::gpio:65]  data = 0
current data: false
[ 19.876698 0 axhal::platform::aarch64_phytium_pi::gpio:58]  data = 256
[ 19.881551 0 axhal::platform::aarch64_phytium_pi::gpio:65]  data = 256
current data: true
[ 20.891012 0 axhal::platform::aarch64_phytium_pi::gpio:58]  data = 256
[ 20.895865 0 axhal::platform::aarch64_phytium_pi::gpio:65]  data = 0
current data: false
[ 21.905240 0 axhal::platform::aarch64_phytium_pi::gpio:58]  data = 256
[ 21.910093 0 axhal::platform::aarch64_phytium_pi::gpio:65]  data = 256
current data: true
[ 22.919554 0 axhal::platform::aarch64_phytium_pi::gpio:58]  data = 256
[ 22.924407 0 axhal::platform::aarch64_phytium_pi::gpio:65]  data = 0
current data: false
[ 23.933782 0 axhal::platform::aarch64_phytium_pi::gpio:58]  data = 256
[ 23.938635 0 axhal::platform::aarch64_phytium_pi::gpio:65]  data = 256
current data: true
[ 24.948097 0 axhal::platform::aarch64_phytium_pi::gpio:58]  data = 256
[ 24.952950 0 axhal::platform::aarch64_phytium_pi::gpio:65]  data = 0
current data: false

led亮

led_off

优化代码

目前驱动代码位于 examples/helloworld/main.c 中，这不是一种正确的做法。参考 modules/axhal/src/platform/aarch64_common/pl011.rs 的实现，在同级目录下实现 pl061.rs。 rust 提供了如 tock_registers 这样的可以用来定义寄存器的crate，用起来！
关机函数实际上是触发了一个异常而导致的关机，当把上一步完成后，换成 axhal::misc::terminate 来优雅的关机！
实验2的完整代码在这儿。

飞腾派驱动开发实验指导书

1.1 GPIO驱动开发

GPIO 介绍

memory mapped io

qemu平台关机实验

实验原理

实验过程

飞腾派点灯实验

实验原理

寄存器定义

实验过程

优化代码

参考资料