Hello,

After upgrade Armbian (4.19.69-meson64) to Armbian Buster with Linux 5.3.11-meson64 warning messages shows up on boot in dmesg:

...
[    1.973932] Key type encrypted registered
[    1.985109] dwc2 c9000000.usb: c9000000.usb supply vusb_d not found, using dummy regulator
[    1.985153] dwc2 c9000000.usb: c9000000.usb supply vusb_a not found, using dummy regulator
[    1.986616] phy phy-c0000000.phy.0: USB ID detect failed!
[    1.986623] phy phy-c0000000.phy.0: phy poweron failed --> -22
[    1.986643] ------------[ cut here ]------------
[    1.986700] WARNING: CPU: 3 PID: 68 at drivers/regulator/core.c:2036 _regulator_put+0x34/0xd8
[    1.986702] Modules linked in:
[    1.986709] CPU: 3 PID: 68 Comm: kworker/3:1 Not tainted 5.3.11-meson64 #19.11.3
[    1.986711] Hardware name: Hardkernel ODROID-C2 (DT)
[    1.986719] Workqueue: events deferred_probe_work_func
[    1.986724] pstate: 60000005 (nZCv daif -PAN -UAO)
[    1.986728] pc : _regulator_put+0x34/0xd8
[    1.986732] lr : _regulator_put+0x34/0xd8
[    1.986733] sp : ffff000011683af0
[    1.986735] x29: ffff000011683af0 x28: 0000000000000000 
[    1.986739] x27: ffff80007f2ac6b8 x26: ffff000011106530 
[    1.986743] x25: 0000000000000000 x24: 0000000000000009 
[    1.986746] x23: ffff000011683bb8 x22: ffff80006a1c2b00 
[    1.986750] x21: ffff0000113916c8 x20: ffff80006a1c2d00 
[    1.986753] x19: ffff80006a1c2d00 x18: ffff0000113ae000 
[    1.986756] x17: 000000003ae42590 x16: 00000000ed672116 
[    1.986760] x15: 00000000fffffff0 x14: ffff0000114be0fa 
[    1.986763] x13: 0000000000000000 x12: ffff0000114bd000 
[    1.986767] x11: ffff0000113ae000 x10: ffff0000114bd748 
[    1.986770] x9 : 0000000000000000 x8 : 0000000000000001 
[    1.986774] x7 : 00000000000000eb x6 : ffff0000114bd000 
[    1.986777] x5 : 0000000000000000 x4 : 0000000000000000 
[    1.986780] x3 : 00000000ffffffff x2 : 3c797d94ab3f0f00 
[    1.986783] x1 : 0000000000000000 x0 : 0000000000000024 
[    1.986787] Call trace:
[    1.986792]  _regulator_put+0x34/0xd8
[    1.986796]  regulator_put+0x2c/0x40
[    1.986800]  regulator_bulk_free+0x30/0x50
[    1.986805]  devm_regulator_bulk_release+0x18/0x20
[    1.986810]  release_nodes+0x1b0/0x220
[    1.986814]  devres_release_all+0x34/0x58
[    1.986818]  really_probe+0x1b8/0x3d0
[    1.986822]  driver_probe_device+0xdc/0x130
[    1.986825]  __device_attach_driver+0x88/0x108
[    1.986828]  bus_for_each_drv+0x78/0xc8
[    1.986831]  __device_attach+0xd4/0x158
[    1.986834]  device_initial_probe+0x10/0x18
[    1.986837]  bus_probe_device+0x90/0x98
[    1.986840]  deferred_probe_work_func+0x88/0xd8
[    1.986846]  process_one_work+0x1e0/0x338
[    1.986850]  worker_thread+0x240/0x440
[    1.986854]  kthread+0x120/0x128
[    1.986859]  ret_from_fork+0x10/0x18
[    1.986861] ---[ end trace 629d4ecc13425951 ]---
[    1.986907] ------------[ cut here ]------------
[    1.986942] WARNING: CPU: 3 PID: 68 at drivers/regulator/core.c:2036 _regulator_put+0x34/0xd8
[    1.986943] Modules linked in:
[    1.986948] CPU: 3 PID: 68 Comm: kworker/3:1 Tainted: G        W         5.3.11-meson64 #19.11.3
[    1.986950] Hardware name: Hardkernel ODROID-C2 (DT)
[    1.986954] Workqueue: events deferred_probe_work_func
[    1.986958] pstate: 60000005 (nZCv daif -PAN -UAO)
[    1.986962] pc : _regulator_put+0x34/0xd8
[    1.986965] lr : _regulator_put+0x34/0xd8
[    1.986967] sp : ffff000011683af0
[    1.986969] x29: ffff000011683af0 x28: 0000000000000000 
[    1.986972] x27: ffff80007f2ac6b8 x26: ffff000011106530 
[    1.986976] x25: 0000000000000000 x24: 0000000000000009 
[    1.986979] x23: ffff000011683bb8 x22: ffff80006a1c2b00 
[    1.986983] x21: ffff0000113916c8 x20: ffff80006a1c2e00 
[    1.986986] x19: ffff80006a1c2e00 x18: ffff0000113ae000 
[    1.986989] x17: 000000003ae42590 x16: 00000000ed672116 
[    1.986993] x15: 00000000fffffff0 x14: ffff0000114be0fa 
[    1.986996] x13: 0000000000000000 x12: ffff0000114bd000 
[    1.987000] x11: ffff0000113ae000 x10: ffff0000114bd748 
[    1.987003] x9 : 0000000000000000 x8 : 0000000000000001 
[    1.987006] x7 : 0000000000000118 x6 : ffff0000114bd000 
[    1.987010] x5 : 0000000000000000 x4 : 0000000000000000 
[    1.987013] x3 : 00000000ffffffff x2 : 3c797d94ab3f0f00 
[    1.987016] x1 : 0000000000000000 x0 : 0000000000000024 
[    1.987019] Call trace:
[    1.987023]  _regulator_put+0x34/0xd8
[    1.987027]  regulator_put+0x2c/0x40
[    1.987030]  regulator_bulk_free+0x30/0x50
[    1.987034]  devm_regulator_bulk_release+0x18/0x20
[    1.987038]  release_nodes+0x1b0/0x220
[    1.987041]  devres_release_all+0x34/0x58
[    1.987044]  really_probe+0x1b8/0x3d0
[    1.987048]  driver_probe_device+0xdc/0x130
[    1.987051]  __device_attach_driver+0x88/0x108
[    1.987053]  bus_for_each_drv+0x78/0xc8
[    1.987056]  __device_attach+0xd4/0x158
[    1.987059]  device_initial_probe+0x10/0x18
[    1.987062]  bus_probe_device+0x90/0x98
[    1.987065]  deferred_probe_work_func+0x88/0xd8
[    1.987069]  process_one_work+0x1e0/0x338
[    1.987072]  worker_thread+0x240/0x440
[    1.987075]  kthread+0x120/0x128
[    1.987078]  ret_from_fork+0x10/0x18
[    1.987081] ---[ end trace 629d4ecc13425952 ]---
[    1.987135] dwc2: probe of c9000000.usb failed with error -22
[    1.987536] dwc2 c9100000.usb: c9100000.usb supply vusb_d not found, using dummy regulator
[    1.987581] dwc2 c9100000.usb: c9100000.usb supply vusb_a not found, using dummy regulator
[    2.024002] mmc0: new HS200 MMC card at address 0001
...

I haven't had any system hangups yet but I am worried.

the same regulator "warnings" do occur with kernel 5.4.1

but syrem didnt hang