Hi,
This is v2 on the attempt to remove misuse of the cache APIs from Ion. The previous version[1] attempted to pull the cache APIs into Ion. This was indicated as the wrong approach and real APIs should be created instead.
The APIs created are kernel_force_cache_clean and kernel_force_cache_invalidate. They force a clean and invalidate of the cache, respectively. The aim was to take the semantics of dma_sync and turn them into something that isn't dma_sync. This series includes a nominal implementation for arm/arm64, mostly for demonstration purposes.
I did review before writing this of whether Ion could just use the DMA mapping APIs to acheive the necessary coherency. The conclusion I came to was that trying to force the Ion code into the DMA model would create more problem than it solved since there wasn't anything like DMA going on. Similarly, none of the existing cache APIs did exactly what was needed either. The closest matches were designed for file cache pages and not drivers.
The series includes conversion of Ion to the new APIs. There are a few other drivers which are calling either arch specific APIs or flush_dcache_page that could be converted as well. The i915 driver could potentially be converted with the addition of an x86 implementation.
Feedback appreciated as always.
Thanks, Laura
[1] https://lkml.kernel.org/g/1464205684-5587-1-git-send-email-labbott@redhat.com
Laura Abbott (5): Documentation: Introduce kernel_force_cache_* APIs arm: Implement ARCH_HAS_FORCE_CACHE arm64: Implement ARCH_HAS_FORCE_CACHE staging: android: ion: Convert to the kernel_force_cache APIs staging: ion: Add support for syncing with DMA_BUF_IOCTL_SYNC
Documentation/cachetlb.txt | 18 +++- arch/arm/include/asm/cacheflush.h | 4 + arch/arm/mm/dma-mapping.c | 119 ------------------------ arch/arm/mm/flush.c | 115 +++++++++++++++++++++++ arch/arm/mm/mm.h | 8 ++ arch/arm64/include/asm/cacheflush.h | 5 + arch/arm64/mm/flush.c | 11 +++ drivers/staging/android/ion/ion.c | 53 +++++++---- drivers/staging/android/ion/ion_carveout_heap.c | 8 +- drivers/staging/android/ion/ion_chunk_heap.c | 12 ++- drivers/staging/android/ion/ion_page_pool.c | 6 +- drivers/staging/android/ion/ion_priv.h | 11 --- drivers/staging/android/ion/ion_system_heap.c | 6 +- include/linux/cacheflush.h | 11 +++ 14 files changed, 225 insertions(+), 162 deletions(-) create mode 100644 include/linux/cacheflush.h