unicam "hangs" - no CSI line data received?

Start with the unicam ISR and receiver-status logs shown in the report, then reproduce ov9281 streaming on the Raspberry Pi CM4 with v4l2-ctl. Compare the stalled run with the later status output and determine whether the missing CSI data or recovery behavior is observable. Done requires a reproducible cause and a defined timeout, error-reporting, or recovery change.

Describe the bug

streaming video from an ov9281 camera, but suddenly no more frames arriving.
Unicam stuck at "lines done 400" (out of 800). No more error messages.

When I simply stop the application and open another application, e.g. v4l2-ctl --stream-mmap I get images immediately.

Would there be a timeout if the camera "hang" and would unicam report it?
What can possibly derail the CSI path that would be this instantly recoverable?
Are there any "error stats" or "missed interrupts"/counter for the unicam block?

Steps to reproduce the behaviour

start streaming from ov9281 camera and wait

Device (s)

Raspberry Pi CM4 Lite

System

 $ vcgencmd version
Dec 12 2022 11:56:56
Copyright (c) 2012 Broadcom
version ed6f6b8fcdc6476410b9cf75d141633461d34bdd (clean) (release) (start)

Raspberry Pi reference 2022-07-28

Linux tester 5.15.84-v8+ #1610 SMP PREEMPT Mon Dec 19 18:54:50 GMT 2022 aarch64 GNU/Linux

Logs

( line breaks only for readability. not shortened)

[12779.337926] unicam fe800000.csi: ISR: ISTA: 0x1, STA: 0x4020, sequence 433, lines done 0
[12779.337948] unicam fe800000.csi: Scheduling dummy buffer for node 0
[12779.341276] unicam fe800000.csi: ISR: ISTA: 0x4, STA: 0x4023, sequence 433, lines done 200
[12779.344308] unicam fe800000.csi: ISR: ISTA: 0x4, STA: 0x4021, sequence 433, lines done 400
[12779.347342] unicam fe800000.csi: ISR: ISTA: 0x4, STA: 0x4023, sequence 433, lines done 600
[12779.350379] unicam fe800000.csi: ISR: ISTA: 0x0, STA: 0xC020, sequence 433, lines done 800
[12779.350545] video0: VIDIOC_DQBUF: 03:32:59.116510 index=1, type=vid-cap, request_fd=0, flags=0x00002001, field=any, sequence=433, memory=mmap, bytesused=1024000, offset/userptr=0xfa000, length=1024000
[12779.350577] timecode=00:00:00 type=0, flags=0x00000000, frames=0, userbits=0x00000000
[12779.354959] video0: VIDIOC_QBUF: 00:00:00.000000 index=1, type=vid-cap, request_fd=0, flags=0x00002003, field=any, sequence=0, memory=mmap, bytesused=1024000, offset/userptr=0xfa000, length=1024000
[12779.355000] timecode=00:00:00 type=0, flags=0x00000000, frames=0, userbits=0x00000000

[12779.377921] unicam fe800000.csi: ISR: ISTA: 0x1, STA: 0x4022, sequence 434, lines done 0
[12779.377942] unicam fe800000.csi: Scheduling dummy buffer for node 0
[12779.381271] unicam fe800000.csi: ISR: ISTA: 0x4, STA: 0x4021, sequence 434, lines done 200
[12779.384301] unicam fe800000.csi: ISR: ISTA: 0x4, STA: 0x4023, sequence 434, lines done 400
[12779.387334] unicam fe800000.csi: ISR: ISTA: 0x4, STA: 0x4021, sequence 434, lines done 600
[12779.390375] unicam fe800000.csi: ISR: ISTA: 0x0, STA: 0xC022, sequence 434, lines done 800
[12779.390448] video0: VIDIOC_DQBUF: 03:32:59.156508 index=0, type=vid-cap, request_fd=0, flags=0x00002001, field=any, sequence=434, memory=mmap, bytesused=1024000, offset/userptr=0x0, length=1024000
[12779.390478] timecode=00:00:00 type=0, flags=0x00000000, frames=0, userbits=0x00000000
[12779.395240] video0: VIDIOC_QBUF: 00:00:00.000000 index=0, type=vid-cap, request_fd=0, flags=0x00002003, field=any, sequence=0, memory=mmap, bytesused=1024000, offset/userptr=0x0, length=1024000
[12779.395283] timecode=00:00:00 type=0, flags=0x00000000, frames=0, userbits=0x00000000

[12779.417916] unicam fe800000.csi: ISR: ISTA: 0x1, STA: 0x4020, sequence 435, lines done 0
[12779.417938] unicam fe800000.csi: Scheduling dummy buffer for node 0
[12779.421269] unicam fe800000.csi: ISR: ISTA: 0x4, STA: 0x4023, sequence 435, lines done 200
[12779.424299] unicam fe800000.csi: ISR: ISTA: 0x4, STA: 0x4021, sequence 435, lines done 400
  ( not shortened - but PC unattended )
[13152.787211] videodev: v4l2_open: video0: open (0)
[13152.787248] video0: VIDIOC_QUERYCAP: driver=unicam, card=unicam, bus=platform:fe800000.csi, version=0x00050f54, capabilities=0xa5a00001, device_caps=0x25200001
[13152.787287] video0: VIDIOC_QUERY_EXT_CTRL: error -25: id=0xc0000000, type=0, name=, min/max=0/0, step=0, default=0, flags=0x00000000, elem_size=0, elems=0, nr_of_dims=0, dims=0,0,0,0
[13152.787328] video0: VIDIOC_TRY_EXT_CTRLS: error -25: which=0x0, count=0, error_idx=0, request_fd=0
[13152.787366] video0: VIDIOC_QUERYCTRL: error -25: id=0x80000000, type=0, name=, min/max=0/0, step=0, default=0, flags=0x00000000
[13152.787401] video0: VIDIOC_G_SELECTION: error -25: type=vid-cap, target=0, flags=0x0, wxh=0x0, x,y=0,0
[13152.787435] video0: VIDIOC_QUERYCAP: driver=unicam, card=unicam, bus=platform:fe800000.csi, version=0x00050f54, capabilities=0xa5a00001, device_caps=0x25200001
[13152.787610] video0: VIDIOC_QUERY_EXT_CTRL: error -25: id=0xc0000000, type=0, name=, min/max=0/0, step=0, default=0, flags=0x00000000, elem_size=0, elems=0, nr_of_dims=0, dims=0,0,0,0
[13152.787652] video0: VIDIOC_QUERYCTRL: error -25: id=0xc0000000, type=0, name=, min/max=0/0, step=0, default=0, flags=0x00000000
[13152.787686] video0: VIDIOC_QUERYCTRL: 
[13152.789122] video0: VIDIOC_QUERYCTRL: error -25: id=0x98092a, type=0, name=, min/max=0/0, step=0, default=0, flags=0x00000000
[13152.789154] video0: VIDIOC_QUERYCTRL: error -25: id=0x8000000, type=0, name=, min/max=0/0, step=0, default=0, flags=0x00000000
[13152.789198] unicam fe800000.csi: =================  START STATUS  =================
[13152.789208] unicam fe800000.csi: -----Receiver status-----
[13152.789215] unicam fe800000.csi: V4L2 width/height:   1280x800
[13152.789223] unicam fe800000.csi: Mediabus format:     00002001
[13152.789230] unicam fe800000.csi: V4L2 format:         59455247
[13152.789237] unicam fe800000.csi: Unpacking/packing:   0 / 0
[13152.789244] unicam fe800000.csi: ----Live data----
[13152.789250] unicam fe800000.csi: Programmed stride:   1280
[13152.789257] unicam fe800000.csi: Detected resolution: 640x800
[13152.789263] unicam fe800000.csi: Write pointer:       db87df00
[13152.789270] unicam fe800000.csi: ==================  END STATUS  ==================
[13152.789276] video0: VIDIOC_LOG_STATUS
[13153.547184] video0: VIDIOC_CROPCAP: error -25: type=vid-cap, bounds wxh=0x0, x,y=0,0, defrect wxh=0x0, x,y=0,0, pixelaspect 0/0
[13153.547237] video0: VIDIOC_CROPCAP: error -25: type=vid-out, bounds wxh=0x0, x,y=0,0, defrect wxh=0x0, x,y=0,0, pixelaspect 0/0
[13153.547288] videodev: v4l2_release: video0: release

Additional context

No response