embedded runtime_error ai_generated true

DMA transfer returns stale data from cache

ID: embedded/dma-buffer-cache-coherency

Also available as: JSON · Markdown
80%Fix Rate
82%Confidence
3Evidence
2023-01-01First Seen

Version Compatibility

VersionStatusIntroducedDeprecatedNotes
any active — — —

Root Cause

DMA reads memory directly but CPU cache holds different data, causing coherency issues.

generic

Workarounds

  1. 88% success Place DMA buffers in non-cacheable MPU region 
    Configure MPU region as Device or Non-cacheable for DMA buffers
  2. 85% success Invalidate/clean D-cache before/after DMA transfers 
    SCB_InvalidateDCache_by_Addr(buf,size) after DMA RX complete

Dead Ends

Common approaches that don't work:

  1. Disable all caching 85% fail

    Destroys performance; D-cache provides 2-10x speedup.

  2. Use volatile keyword on DMA buffers 90% fail

    volatile only prevents compiler optimization, not hardware cache.