imx6dl rtc doesn't work

[gwgw]

Hello, I'm using imx6dl, and when I use cmd 'hwclock --systohc', all of sudden the processor stalls intermittently.

Also the processor kept printing below kernel logs.

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[ 40.399011] INFO: rcu_sched self-detected stall on CPU
[ 40.404185] 1: (2100 ticks this GP) idle=70d/140000000000001/0 softirq=1016/1016 fqs=2100
[ 40.409012] INFO: rcu_sched detected stalls on CPUs/tasks:
[ 40.409020] 1: (2100 ticks this GP) idle=70d/140000000000001/0 softirq=1016/1016 fqs=2100
[ 40.409028] (detected by 0, t=2102 jiffies, g=73, c=72, q=3434)
[ 40.409031] Task dump for CPU 1:
[ 40.409038] kworker/1:1 R running 0 45 2 0x00000002
[ 40.409059] Workqueue: events rtc_timer_do_work
[ 40.409084] [<804d5e48>] (__schedule) from [<00000008>] (0x8)
[ 40.452214] (t=2106 jiffies g=73 c=72 q=3434)
[ 40.456763] Task dump for CPU 1:
[ 40.459992] kworker/1:1 R running 0 45 2 0x00000002
[ 40.466389] Workqueue: events rtc_timer_do_work
[ 40.470956] [<80015fd4>] (unwind_backtrace) from [<800120c4>] (show_stack+0x10/0x14)
[ 40.478714] [<800120c4>] (show_stack) from [<80069230>] (rcu_dump_cpu_stacks+0x90/0xd0)
[ 40.486731] [<80069230>] (rcu_dump_cpu_stacks) from [<8006c23c>] (rcu_check_callbacks+0x40c/0x738)
[ 40.495700] [<8006c23c>] (rcu_check_callbacks) from [<8006e6d0>] (update_process_times+0x30/0x5c)
[ 40.504584] [<8006e6d0>] (update_process_times) from [<8007d824>] (tick_sched_timer+0x44/0x84)
[ 40.513206] [<8007d824>] (tick_sched_timer) from [<8006ee70>] (__run_hrtimer+0x44/0xd0)
[ 40.521219] [<8006ee70>] (__run_hrtimer) from [<8006f68c>] (hrtimer_interrupt+0x10c/0x288)
[ 40.529489] [<8006f68c>] (hrtimer_interrupt) from [<8001568c>] (twd_handler+0x2c/0x40)
[ 40.537416] [<8001568c>] (twd_handler) from [<80064870>] (handle_percpu_devid_irq+0x68/0x84)
[ 40.545864] [<80064870>] (handle_percpu_devid_irq) from [<80060ddc>] (generic_handle_irq+0x20/0x30)
[ 40.554917] [<80060ddc>] (generic_handle_irq) from [<80060ed8>] (__handle_domain_irq+0x54/0xac)
[ 40.563622] [<80060ed8>] (__handle_domain_irq) from [<80009378>] (gic_handle_irq+0x20/0x60)
[ 40.571980] [<80009378>] (gic_handle_irq) from [<80012b40>] (__irq_svc+0x40/0x54)
[ 40.579465] Exception stack(0xb5137da8 to 0xb5137df0)
[ 40.584524] 7da0: b502ca00 b4fbf900 00000001 00007091 60000013 00000000
[ 40.592705] 7dc0: b5137e14 b502b680 b502b71c b502b400 00000000 b5137eac 802c4d30 b5137df0
[ 40.600884] 7de0: 804da178 804da17c 60000013 ffffffff
[ 40.605950] [<80012b40>] (__irq_svc) from [<804da17c>] (_raw_spin_unlock_irqrestore+0x10/0x14)
[ 40.614576] [<804da17c>] (_raw_spin_unlock_irqrestore) from [<802bffe4>] (regmap_read+0x54/0x5c)
[ 40.623375] [<802bffe4>] (regmap_read) from [<803670c8>] (snvs_rtc_alarm_irq_enable+0x80/0xb0)
[ 40.631997] [<803670c8>] (snvs_rtc_alarm_irq_enable) from [<803651e8>] (rtc_timer_do_work+0x110/0x1c0)
[ 40.641317] [<803651e8>] (rtc_timer_do_work) from [<8003d6b4>] (process_one_work+0x120/0x324)
[ 40.649851] [<8003d6b4>] (process_one_work) from [<8003da24>] (worker_thread+0x138/0x470)
[ 40.658040] [<8003da24>] (worker_thread) from [<800423cc>] (kthread+0xd8/0xf4)
[ 40.665272] [<800423cc>] (kthread) from [<8000f328>] (ret_from_fork+0x14/0x2c)

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[ 1.040042] snvs_rtc 20cc000.snvs:snvs-rtc-lp: rtc core: registered 20cc000.snvs:snvs-r as rtc0

[ 1.361352] snvs_rtc 20cc000.snvs:snvs-rtc-lp: setting system clock to 1970-01-01 00:00:00 UTC (0)

when I look above logs, I couldn't find a specific problem with RTC.

we followed the instructions to use RTC on the document "IMX6DQ6SDLHDG Rev. 2"

I can't find what the exact problem is.

Thank you in advance.