Tweaking Device Drivers for Achieving Real-Time Performance in Embedded...
summary
RT Linux on an application processor is tuned to reach MCU-like determinism for SPI devices by tracing with trace-cmd + KernelShark, cyclictest and lmbench, finding that deferred work in the DMA engine (per-channel tasklets and udma status checks) causes rare spikes from expected ~800 µs to 5–100 ms. Removing non‑RT callbacks, promoting workqueues where needed, and using the SPI controller’s local completion event (instead of waiting on DMA callbacks) reduces jitter to ~800 µs typical and peaks under ~400 µs in host workloads; test artifacts live on GitHub.
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chapters (6)
- 0:00Start
- 1:18Problem Statement
- 7:57RT Linux System Tuning
- 10:30SPI Target mode | Challenges
- 15:14SPI Controller driver | Analysis
- 15:31DMA driver analysis | Finding Bottlenecks
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