Quoting Nicolas Saenz Julienne (2021-03-25 11:25:24)

On Thu, 2021-03-25 at 14:31 +0100, Marek Szyprowski wrote:

quoted

Hi

On 10.02.2021 12:44, Tudor Ambarus wrote:

quoted

This is a follow-up for:
commit 3c9ea42802a1 ("clk: Mark fwnodes when their clock provider is added/removed")

The above commit updated the deprecated of_clk_add_provider(),
but missed to update the preferred of_clk_add_hw_provider().
Update it now.

Signed-off-by: Tudor Ambarus <redacted>

This patch, which landed in linux-next as commit 6579c8d97ad7 ("clk: 
Mark fwnodes when their clock provider is added") causes the following 
NULL pointer dereference on Raspberry Pi 3b+ boards:

--->8---

raspberrypi-firmware soc:firmware: Attached to firmware from 
2020-01-06T13:05:25
Unable to handle kernel NULL pointer dereference at virtual address 
0000000000000050
Mem abort info:
   ESR = 0x96000004
   EC = 0x25: DABT (current EL), IL = 32 bits
   SET = 0, FnV = 0
   EA = 0, S1PTW = 0
Data abort info:
   ISV = 0, ISS = 0x00000004
   CM = 0, WnR = 0
[0000000000000050] user address but active_mm is swapper
Internal error: Oops: 96000004 [#1] PREEMPT SMP
Modules linked in:
CPU: 0 PID: 10 Comm: kworker/0:1 Not tainted 5.12.0-rc4+ #2764
Hardware name: Raspberry Pi 3 Model B (DT)
Workqueue: events deferred_probe_work_func
pstate: 00000005 (nzcv daif -PAN -UAO -TCO BTYPE=--)
pc : of_clk_add_hw_provider+0xac/0xe8
lr : of_clk_add_hw_provider+0x94/0xe8
sp : ffff8000130936b0
x29: ffff8000130936b0 x28: ffff800012494e04
x27: ffff00003b18cb05 x26: ffff00003aa5c010
x25: 0000000000000000 x24: 0000000000000000
x23: ffff00003aa1e380 x22: ffff8000106830d0
x21: ffff80001233f180 x20: 0000000000000018
x19: 0000000000000000 x18: ffff8000124d38b0
x17: 0000000000000013 x16: 0000000000000014
x15: ffff8000125758b0 x14: 00000000000184e0
x13: 000000000000292e x12: ffff80001258dd98
x11: 0000000000000001 x10: 0101010101010101
x9 : ffff80001233f288 x8 : 7f7f7f7f7f7f7f7f
x7 : fefefefeff6c626f x6 : 5d636d8080808080
x5 : 00000000006d635d x4 : 0000000000000000
x3 : 0000000000000000 x2 : 540eb5edae191600
x1 : 0000000000000000 x0 : 0000000000000000
Call trace:
  of_clk_add_hw_provider+0xac/0xe8
  devm_of_clk_add_hw_provider+0x5c/0xb8
  raspberrypi_clk_probe+0x110/0x210
  platform_probe+0x90/0xd8
  really_probe+0x108/0x3c0
  driver_probe_device+0x60/0xc0
  __device_attach_driver+0x9c/0xd0
  bus_for_each_drv+0x70/0xc8
  __device_attach+0xec/0x150
  device_initial_probe+0x10/0x18
  bus_probe_device+0x94/0xa0
  device_add+0x47c/0x780
  platform_device_add+0x110/0x248
  platform_device_register_full+0x120/0x150
  rpi_firmware_probe+0x158/0x1f8
  platform_probe+0x90/0xd8
  really_probe+0x108/0x3c0
  driver_probe_device+0x60/0xc0
  __device_attach_driver+0x9c/0xd0
  bus_for_each_drv+0x70/0xc8
  __device_attach+0xec/0x150
  device_initial_probe+0x10/0x18
  bus_probe_device+0x94/0xa0
  deferred_probe_work_func+0x70/0xa8
  process_one_work+0x2a8/0x718
  worker_thread+0x48/0x460
  kthread+0x134/0x160
  ret_from_fork+0x10/0x18
Code: b1006294 540000c0 b140069f 54000088 (3940e280)
---[ end trace 7ead5ec2f0c51cfe ]---

This patch mainly revealed that clk/bcm/clk-raspberrypi.c driver calls 
devm_of_clk_add_hw_provider(), with a device pointer, which has a NULL 
dev->of_node. I'm not sure if adding a check for a NULL np in 
of_clk_add_hw_provider() is a right fix, though.

I believe the right fix is not to call 'devm_of_clk_add_hw_provider()' if
'pdev->dev.of_node == NULL'. In such case, which is RPi3's, only the CPU clock
is used, and it's defined and queried later through
devm_clk_hw_register_clkdev().

@Marek, I don't mind taking care of it if it's OK with you.

Ah I see this is related to the patch I just reviewed. Can you reference
this in the commit text? And instead of putting the change into the clk
provider let's check for NULL 'np' in of_clk_add_hw_provider() instead
and return 0 if there's nothing to do. That way we don't visit this
problem over and over again.