[00/10] libcamera: software_isp: gpu: Add go faster stripes
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Message ID 20260624085849.873784-1-bryan.odonoghue@linaro.org
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  • libcamera: software_isp: gpu: Add go faster stripes
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Bryan O'Donoghue June 24, 2026, 8:58 a.m. UTC 
Following on from Robert Mader's ask to bring forward GPUISP multi-pass
cache operations to mainline first, I've done some work to enable that.

This series implements an input/output texture caching scheme which results
in an overall absolute 4.5 millisecond - roughly improvement in performance
per processed frame. This is a bit of an odd result as I was expecting to
shave a particular % off of each frame in the order of 20% or so. My best
guess is that particular paths we are optimising here are around texture
generation and these are "fixed costs" on the CPU side.

One very welcome outcome of this series is genuine zero-copy on dma-buf
paths we can support it on i.e. on paths where the CSI2 and GPU strides
agree.

The numbers cited in my example are for non dma-buf handle upload and
dma-buf handle render-to-texture on the output so, in fact I'd expect to
see a much larger improvement on systems where dma-buf handle is used on
both paths.

As it is on my test reference systems I have a 50% improvement per frame
for one system, a 20% improvement on another system or we could view it as
a fixed 4.5 millisecond improvement on both.

I implemented the cache around V4L2BufferCache as per Barnabas' suggestion,
including a fixed cache size.

Bryan O'Donoghue (10):
  libcamera: v4l2_videodevice: Output cache hit as a parameter
  libcamera: egl: Add new helper attachTextureToFBO
  libcamera: egl: Extend eGL::createTexture2D to understand floats
  libcamera: egl: Rename createTexture2D to createInputTexture2D
  libcamera: egl: Add createOutputTexture2D
  libcamera: egl: Add updateInputTexture2D
  libcamera: egl: Add activateBindTexture
  libcamera: software_isp: debayer_egl: Pass eglImage as parameter to
    setShaderVariables
  libcamera: software_isp: debayer_egl: Flag dmabuf use once per session
    not for every frame
  libcamera: software_isp: debayer_egl: Implement input/output frame
    caching mechanism

 include/libcamera/internal/egl.h              |   7 +-
 include/libcamera/internal/v4l2_videodevice.h |   2 +-
 src/libcamera/egl.cpp                         | 126 +++++++++++++++---
 src/libcamera/software_isp/debayer_egl.cpp    | 119 +++++++++++++----
 src/libcamera/software_isp/debayer_egl.h      |  16 ++-
 src/libcamera/v4l2_videodevice.cpp            |   9 +-
 6 files changed, 228 insertions(+), 51 deletions(-)