[0/3] rkisp1: Update exposure limits on vblank change
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Message ID 20251017-exposure-limits-v1-0-6288cd86e719@ideasonboard.com
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  • rkisp1: Update exposure limits on vblank change
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Jacopo Mondi Oct. 17, 2025, 9 a.m. UTC 
By definition, the exposure time that can be programmed on a sensor is
limited by the frame duration and whenever the frame duration is
updated, the exposure time limits should be updated as well.

This is not the case in the RkISP1 IPA, where the exposure limits
are computed at configure() time and never updated.

This has two implications:
1) The AGC algorithms will always operate with an exposure time bound to
   the frame duration programmed at startup time
2) The Camera::controls() limits are not updated to reflect the new
   constraints

This series addresses the above issues with 2 patches.

The first one for the IPA simply updates the exposure limts whenever the
VBLANK changes in response to a FrameDurationLimits change.

The second one for the IPA/pipeline introduces a new operation in the
IPA interface which the pipeline handler calls to have the limits of the
controls registered by the IPA updated.

The timing of these two operations is critical.

The IPA limits should be updated whenever a new VBLANK is computed. The
actual blanking value on the sensor will be changed with a few
frames of latency by DelayedControls, but for the IPA this is not
relevant as all the computations for the 'next' frames will be delayed
by the same latency and should use the new limits.

The Camera::controls() limits should instead be updated when the Request
with the updated FrameDurationLimits completes. For this reason the new
'updateControlsLimits()' IPA operation is called before completing a
Request on the pipeline handler side.

Finally, the last patch, not meant for inclusion, validates that the
Camera::controls() limits are updated correctly. The IPA limits update
has been visually validated with camshark by tuning the
FrameDurationLimits control and verifying the AGC algorithm limits are
updated accordingly.

Signed-off-by: Jacopo Mondi <jacopo.mondi@ideasonboard.com>
---
Jacopo Mondi (3):
      ipa: rkisp1: Update exposure limits on vblank change
      libcamera: rkisp1: Update camera::controls() on limit changes
      DNI: cam: Test Camera::controls() update with capture script

 change-frame-duration.yaml               |  4 +++
 include/libcamera/ipa/rkisp1.mojom       |  2 ++
 src/apps/cam/camera_session.cpp          | 21 ++++++++++++
 src/ipa/rkisp1/algorithms/agc.cpp        |  3 ++
 src/ipa/rkisp1/ipa_context.h             |  5 ++-
 src/ipa/rkisp1/rkisp1.cpp                | 57 ++++++++++++++++++++++++++++++--
 src/libcamera/pipeline/rkisp1/rkisp1.cpp |  3 ++
 7 files changed, 91 insertions(+), 4 deletions(-)
---
base-commit: b9fa6e0e61d3ea605fe4b1201ede5745cd5800e5
change-id: 20251017-exposure-limits-5c48252fe548

Best regards,