From: Barry Song <baohua@xxxxxxxxxx>
Currently, arch_sync_dma_for_cpu and arch_sync_dma_for_device
always wait for the completion of each DMA buffer. That is,
issuing the DMA sync and waiting for completion is done in a
single API call.
For scatter-gather lists with multiple entries, this means
issuing and waiting is repeated for each entry, which can hurt
performance. Architectures like ARM64 may be able to issue all
DMA sync operations for all entries first and then wait for
completion together.
To address this, arch_sync_dma_for_* now issues DMA operations in
batch, followed by a flush. On ARM64, the flush is implemented
using a dsb instruction within arch_sync_dma_flush().
For now, add arch_sync_dma_flush() after each
arch_sync_dma_for_*() call. arch_sync_dma_flush() is defined as a
no-op on all architectures except arm64, so this patch does not
change existing behavior. Subsequent patches will introduce true
batching for SG DMA buffers.
Cc: Leon Romanovsky <leon@xxxxxxxxxx>
Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
Cc: Will Deacon <will@xxxxxxxxxx>
Cc: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
Cc: Robin Murphy <robin.murphy@xxxxxxx>
Cc: Ada Couprie Diaz <ada.coupriediaz@xxxxxxx>
Cc: Ard Biesheuvel <ardb@xxxxxxxxxx>
Cc: Marc Zyngier <maz@xxxxxxxxxx>
Cc: Anshuman Khandual <anshuman.khandual@xxxxxxx>
Cc: Ryan Roberts <ryan.roberts@xxxxxxx>
Cc: Suren Baghdasaryan <surenb@xxxxxxxxxx>
Cc: Joerg Roedel <joro@xxxxxxxxxx>
Cc: Juergen Gross <jgross@xxxxxxxx>
Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>
Cc: Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx>
Cc: Tangquan Zheng <zhengtangquan@xxxxxxxx>
Signed-off-by: Barry Song <baohua@xxxxxxxxxx>
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