Kernel Panic when trying to capture camera with ffmpeg on imx8mp

[Maud Spierings <maudspierings@gocontroll.com>]

Dear Readers,

I'm attempting to get a raspberry pi camera working with our imx8mp 
based platform. However when running ` ffmpeg -f v4l2 -i /dev/video2 
-c:v libx264 -preset medium -crf 23 output.mp4`. It results in a kernel 
panic.

Kernel version: 6.12.41
ffmpeg version: 7:7.1.1-1+b1 (Debian Trixie)
v4l2-ctl -d 2 -D:
Driver Info:
Driver name      : mxc-isi
Card type        : mxc-isi-cap
Bus info         : platform:32e00000.isi
Driver version   : 6.12.41
Capabilities     : 0xa4201000
Video Capture Multiplanar
I/O MC
Streaming
Extended Pix Format
Device Capabilities
Device Caps      : 0x24201000
Video Capture Multiplanar
I/O MC
Streaming
Extended Pix Format
Media Driver Info:
Driver name      : mxc-isi
Model            : FSL Capture Media Device
Serial           :
Bus info         : platform:32e00000.isi
Media version    : 6.12.41
Hardware revision: 0x00000000 (0)
Driver version   : 6.12.41
Interface Info:
ID               : 0x03000017
Type             : V4L Video
Entity Info:
ID               : 0x00000015 (21)
Name             : mxc_isi.1.capture
Function         : V4L2 I/O
Pad 0x01000016   : 0: Sink
   Link 0x02000019: from remote pad 0x1000014 of entity 'mxc_isi.1' 
(Video Pixel Formatter): Data, Enabled, Immutable


Panic:
  134.378107] Unable to handle kernel NULL pointer dereference at 
virtual address 0000000000000020
[  134.386921] Mem abort info:
[  134.389717]   ESR = 0x0000000096000004
[  134.393499]   EC = 0x25: DABT (current EL), IL = 32 bits
[  134.398835]   SET = 0, FnV = 0
[  134.401925]   EA = 0, S1PTW = 0
[  134.405068]   FSC = 0x04: level 0 translation fault
[  134.409956] Data abort info:
[  134.412841]   ISV = 0, ISS = 0x00000004, ISS2 = 0x00000000
[  134.418345]   CM = 0, WnR = 0, TnD = 0, TagAccess = 0
[  134.423414]   GCS = 0, Overlay = 0, DirtyBit = 0, Xs = 0
[  134.428749] user pgtable: 4k pages, 48-bit VAs, pgdp=0000000044ffb000
[  134.435225] [0000000000000020] pgd=0000000000000000, p4d=0000000000000000
[  134.442047] Internal error: Oops: 0000000096000004 [#1] PREEMPT SMP
[  134.448326] Modules linked in: g_serial
[  134.452176] CPU: 1 UID: 0 PID: 445 Comm: ffmpeg Not tainted 
6.12.41-GOcontroll #36
[  134.459750] Hardware name: GOcontroll Moduline Display with camera 
test board (DT)
[  134.467321] pstate: 60000005 (nZCv daif -PAN -UAO -TCO -DIT -SSBS 
BTYPE=--)
[  134.474285] pc : mxc_isi_crossbar_xlate_streams+0xac/0x170
[  134.479782] lr : mxc_isi_crossbar_xlate_streams+0xa8/0x170
[  134.485273] sp : ffff8000819738d0
[  134.488586] x29: ffff8000819738d0 x28: ffff800081973948 x27: 
ffff800081973950
[  134.495734] x26: ffff80008197394c x25: ffff0000028ab0a8 x24: 
0000000000000001
[  134.502878] x23: 0000000000000001 x22: 0000000000000001 x21: 
0000000000000001
[  134.510023] x20: 0000000000000004 x19: ffff00000351c458 x18: 
0000000000000002
[  134.517165] x17: 00007dff35433000 x16: ffff8000815df000 x15: 
0000000000000001
[  134.524310] x14: 0000000000000000 x13: 00000000000629fd x12: 
ffff8000812ae000
[  134.531455] x11: 0000000000000001 x10: 0000000000000001 x9 : 
0000000000000004
[  134.538599] x8 : ffff000002610d2c x7 : 0000000000000000 x6 : 
ffff80008197394c
[  134.545742] x5 : ffff000002611e40 x4 : 000000000fffffff x3 : 
ffff0000028ab110
[  134.552887] x2 : ffff0000028ab110 x1 : 0000000000000000 x0 : 
0000000000000000
[  134.560034] Call trace:
[  134.562482]  mxc_isi_crossbar_xlate_streams+0xac/0x170
[  134.567626]  mxc_isi_crossbar_enable_streams+0x50/0x18c
[  134.572859]  v4l2_subdev_enable_streams+0x180/0x3b0
[  134.577740]  mxc_isi_pipe_enable+0x1e4/0x260
[  134.582018]  mxc_isi_vb2_start_streaming+0xa0/0x108
[  134.586898]  vb2_start_streaming+0x6c/0x178
[  134.591084]  vb2_core_streamon+0xd8/0x1bc
[  134.595094]  vb2_streamon+0x18/0x64
[  134.598588]  mxc_isi_video_streamon+0x318/0x3a0
[  134.603119]  v4l_streamon+0x24/0x30
[  134.606615]  __video_do_ioctl+0x40c/0x4a0
[  134.610627]  video_usercopy+0x354/0x658
[  134.614465]  video_ioctl2+0x18/0x40
[  134.617956]  v4l2_ioctl+0x40/0x60
[  134.621276]  __arm64_sys_ioctl+0xbc/0xdc
[  134.625202]  invoke_syscall+0x48/0x104
[  134.628961]  el0_svc_common.constprop.0+0x40/0xe0
[  134.633669]  do_el0_svc+0x1c/0x28
[  134.636987]  el0_svc+0x30/0x100
[  134.640136]  el0t_64_sync_handler+0x120/0x12c
[  134.644497]  el0t_64_sync+0x190/0x194
[  134.648168] Code: d37a7f00 8b000020 97ff155f aa0003e1 (f9401000)
[  134.654264] ---[ end trace 0000000000000000 ]---
[  134.658883] Kernel panic - not syncing: Oops: Fatal exception
[  134.664630] SMP: stopping secondary CPUs
[  134.668558] Kernel Offset: disabled
[  134.672047] CPU features: 0x00,00000080,00200000,4200420b
[  134.677448] Memory Limit: none

Other ffmpeg output:
[video4linux2,v4l2 @ 0xaaaacfe2bc60] ioctl(VIDIOC_G_PARM): Inappropriate 
ioctl for device
[video4linux2,v4l2 @ 0xaaaacfe2bc60] Time per frame unknown

Likely I'm doing something very stupid because I don't know what I'm 
doing. But all the other /dev/videoX entries just result in an error. 
Except for this specific one that reproducibly panics.

My devicetree setup is practically identical to the one in 
freescale/imx8mp-venice-gw74xx-imx219.dtso (different i2c bus and 
regulator gpio only)

I'll try and figure out which variable the guilty one is.

Kind Regards,
Maud