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CONFIG_DMA_CACHE_RWFO: Enable read/write for ownership DMA cache maintenance

General informations

The Linux kernel configuration item CONFIG_DMA_CACHE_RWFO:

Help text

The Snoop Control Unit on ARM11MPCore does not detect the cache maintenance operations and the dma_{map,unmap}_area() functions may leave stale cache entries on other CPUs. By enabling this option, Read or Write For Ownership in the ARMv6 DMA cache maintenance functions is performed. These LDR/STR instructions change the cache line state to shared or modified so that the cache operation has the desired effect.

Note that the workaround is only valid on processors that do not perform speculative loads into the D-cache. For such processors, if cache maintenance operations are not broadcast in hardware, other workarounds are needed (e.g. cache maintenance broadcasting in software via FIQ).

Hardware

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