鸿蒙Harmony系统时钟源码解析 - HarmonyOS技术社区 - 电子技术论坛 - 广受欢迎的专业电子论坛

Bright_ML

2021-01-06 17:26:26

鸿蒙 HarmonyOS 时钟

一.系统时钟初始化 1.main函数的各种调用,验证参数

kernelliteos_aplatformmain.c->main()

kernelliteos_akernelcommonlos_config.c->OsMain()

kernelliteos_aarcharmarmsrclos_hw_tick.c->OsTickInit()

systemClock //vendor里设置的是50000000
tickPerSecond //鸿蒙默认设置的是100
LITE_OS_SEC_TEXT_INIT UINT32 OsTickInit(UINT32 systemClock, UINT32 tickPerSecond)
{ //只是验证了下传入的这两个参数,并未使用
HalClockInit();
return LOS_OK;
}

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2.先获取当前时钟频率,注册中断

kernelliteos_aplatformhwarmtimerarm_genericarm_generic_timer.c

OS_TICK_INT_NUM//中断号,在vendor******boardincludeasmhal_platform_ints.h下定义,查手册确定
MIN_INTERRUPT_PRIORITY//优先级
OsTickEntry//中断函数
LITE_OS_SEC_TEXT_INIT VOID HalClockInit(VOID)
{ ...
g_sysClock = HalClockFreqRead(); //先获取当前时钟频率
//调用LOS_HwiCreate函数新建中断，系统中断由它注册
ret = LOS_HwiCreate(OS_TICK_INT_NUM, MIN_INTERRUPT_PRIORITY, 0, OsTickEntry, 0);//参数1:中断号、参数4:执行函数
//这个函数就不深入了，大体就是将中断号好和对应的执行函数放到一个数组
//比如这里就是，当发生OS_TICK_INT_NUM这个中断时，执行OsTickEntry()函数
...
}

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二.时钟中断的执行函数OsTickEntry()

kernelliteos_aplatformhwarmtimerarm_genericarm_generic_timer.c

不过此时这是注册了这个函数，时钟并未启动，得执行了（三.启动时钟）之后才会调用这个函数

LITE_OS_SEC_TEXT VOID OsTickEntry(VOID)
{
TimerCtlWrite(0);
OsTickHandler();
TimerCvalWrite(TimerCvalRead() + OS_CYCLE_PER_TICK);
TimerCtlWrite(1);
//使用最后一个cval生成下一个tick的时间是绝对和准确的。不要使用tval来驱动一般时间，在这种情况下tick会变慢。
}

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三.启动时钟

main() => OsStart(VOID) => OsTickStart() => HalClockStart(VOID)

kernelliteos_aplatformhwarmtimerarm_genericarm_generic_timer.c => HalClockStart(VOID)

//树莓派2b没有GIC所以这个函数要爆改
LITE_OS_SEC_TEXT_INIT VOID HalClockStart(VOID)
{
HalIrqUnmask(OS_TICK_INT_NUM); //wendor里定义的 OS_TICK_INT_NUM = 29
TimerCtlWrite(0);
TimerTvalWrite(OS_CYCLE_PER_TICK);
TimerCtlWrite(1);
}

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1. HalIrqUnmask; //接收中断（通过设置寄存器，允许CPU响应该中断）

HalIrqUnmask(OS_TICK_INT_NUM);
HalIrqUnmask(29);
GIC_REG_32(GICD_ISENABLER(29 >> 5)) = 1U << (29 % 32);
(GICD_ISENABLER(29 >> 5))拆开
GIC_REG_32(GICD_OFFSET + 0x100 + (29 >> 5) * 4) = 1U << (29 % 32);/* 中断使能 Registers */
GIC_REG_32拆开，(29 % 32)=1D
GIC_BASE_ADDR + (GICD_OFFSET + 0x100 + (29 >> 5) * 4) = 1U << (29 % 32)
#define GIC_BASE_ADDR IO_DEVICE_ADDR(0x3F00A100)
#define GICD_OFFSET 0x1000 /* interrupt distributor offset */

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2.TimerCtlWrite(0); //关闭Timer

WRITE_TIMER_REG32(TIMER_REG_CTL, 0);
```
ARM_SYSREG_WRITE(TIMER_REG_CTL, 0)
```
ARM_SYSREG_WRITE(TIMER_REG(_CTL), 0)
ARM_SYSREG_WRITE(CP15_REG(c14, 0, c2, 1)), 0)
"mcr " (CP15_REG(c14, 0, c2, 1) :: "r" (val)
反汇编
r8 0
mcr p15, #0, r8, c14, c2, #1 CNTP_CTL,PL1物理定时器控制寄存器

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3.TimerTvalWrite(OS_CYCLE_PER_TICK); //设置Tval

反汇编
r0 192000
mcr p15, #0, r0, c14, c2, #0 CNTP_TVAL,PL1物理时间值寄存器

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4.TimerCtlWrite(1); //再开启Timer

反汇编
r5 1
mcr p15, #0, r5, c14, c2, #1 CNTP_CTL,PL1物理定时器控制寄存器

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代码移植

Z:brightharmony-100askkernelliteos_aplatformhwarminterruptgicgic_v2.c

VOID HalIrqUnmask(UINT32 vector)
{
if ((vector > OS_USER_HWI_MAX) || (vector < OS_USER_HWI_MIN)) {
return;
}
//GIC_REG_32(GICD_ISENABLER(vector >> 5)) = 1U << (vector % 32); //替换
*(volatile UINT32 *)((UINTPTR)IO_DEVICE_ADDR(0x3F00B218)) = 1; //使能ARM Timer IRQ
}

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Z:brightharmony-100askkernelliteos_aplatformhwarmtimerarm_genericarm_generic_timer.c

STATIC_INLINE VOID TimerCtlWrite(UINT32 cntpCtl)
{
//WRITE_TIMER_REG32(TIMER_REG_CTL, cntpCtl);//替换
if(cntpCtl == 0){
*(volatile UINT32 *)((UINTPTR)IO_DEVICE_ADDR(0x3F00B408)) = 0x003E0000;
}
else
{
*(volatile UINT32 *)((UINTPTR)IO_DEVICE_ADDR(0x3F00B408)) = 0x003E00A2;
}
}

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Z:brightharmony-100askkernelliteos_aplatformhwarmtimerarm_genericarm_generic_timer.c

STATIC_INLINE VOID TimerTvalWrite(UINT32 tval)
{
//WRITE_TIMER_REG32(TIMER_REG_TVAL, tval);//替换
*(volatile UINT32 *)((UINTPTR)IO_DEVICE_ADDR(0x3F00B400)) = tval; //设置倒计时时间，鸿蒙是10ms
}

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[文章]鸿蒙Harmony系统时钟源码解析

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