上一篇：init_IRQ()：設定中斷棧，呼叫of_irq_init初始化中斷控制器，其中會註冊CPUHP_AP_IRQ_GIC_STARTING的回撥函式gic_starting_cpu

https://www.cnblogs.com/zhangzhiwei122/p/16092659.html

參考-總流程：https://www.cnblogs.com/pengdonglin137/p/11925299.html

10、time_init() 呼叫 drivers/clocksource/arm_arch_timer.c 中 arch_timer_of_init 註冊CPUHP_AP_ARM_ARCH_TIMER_STARTING的回撥函式

start_kernel -> time_init

848asmlinkage __visible void __init __no_sanitize_address start_kernel(void)
849{

 972        time_init();

time_init

arch/arm64/kernel/time.c

59 - 呼叫 timer_probe - 在  drivers/clocksource/timer-probe.c

  54void __init time_init(void)
  55{
  56        u32 arch_timer_rate;
  
 
57
  58        of_clk_init(NULL);
  59        timer_probe();

  71}

timer_probe

drivers/clocksource/timer-probe.c

  11extern struct of_device_id __timer_of_table[];

  16void __init timer_probe(void)
  17{

  24        for_each_matching_node_and_match(np, __timer_of_table, &match) {

  28                init_func_ret = match->data;
  
 
29
  30                ret = init_func_ret(np);
  31                if (ret) {
  32                        if (ret != -EPROBE_DEFER)
  33                                pr_err("Failed to initialize '%pOF': %d\n", np,
  34                                       ret);
  35                        continue;
  36                }
  37
  38                timers++;
  39        }
  40
  41        timers += acpi_probe_device_table(timer);
  42
  43        if (!timers)
  44                pr_crit("%s: no matching timers found\n", __func__);
  45}

24 -  for each mathing node and match 掃描 dtb 中的 節點，匹配 __timer_of_table 陣列中的  of_device_id 物件。

    __timer_of_table 指向 kernel 映象中的 特殊 節 __timer_of_table，這個節裡面都是  kernel 中編譯的  timer 的of_device_id 物件。

示例：

drivers/clocksource/arm_arch_timer.c ， 匹配 dtb 中  arm,armv7-timer 節點

1324TIMER_OF_DECLARE(armv7_arch_timer, "arm,armv7-timer", arch_timer_of_init);
1325TIMER_OF_DECLARE(armv8_arch_timer, "arm,armv8-timer", arch_timer_of_init);
1326

28 和 30 行，匹配成功後，呼叫 of_device_id 物件的 data 欄位 指示的函式。 如上面示例，就是  drivers/clocksource/arm_arch_timer.c   arch_timer_of_init

 arch_timer_of_init

drivers/clocksource/arm_arch_timer.c

1272 的 arch_timer_of_init 呼叫1090 的 arch_timer_register

1090 的arch_timer_register 在1138 處使用 cpu hotplug 模組函式，註冊 CPUHP_AP_ARM_ARCH_TIMER_STARTING 回撥 arch_timer_starting_cpu 和 arch_timer_dying_cpu

1089
1090static int __init arch_timer_register(void)
1091{

1137        /* Register and immediately configure the timer on the boot CPU */
1138        err = cpuhp_setup_state(CPUHP_AP_ARM_ARCH_TIMER_STARTING,
1139                                "clockevents/arm/arch_timer:starting",
1140                                arch_timer_starting_cpu, arch_timer_dying_cpu);

1158}



1272static int __init arch_timer_of_init(struct device_node *np)
1273{

1315        ret = arch_timer_register();
1316        if (ret)
1317                return ret;
1323}