[ARM] Don't call consistent_sync() for DMA coherent memory (7f8e3354) · Commits · 戴 / test

Memory allocated by the coherent memory allocators will be marked uncacheable, which means it's pointless calling consistent_sync() to perform cache maintainence on this memory; it's just a waste of CPU cycles. Moreover, with the (subsequent) merge of outer cache support, it actually breaks things to call consistent_sync() on anything but direct-mapped memory. Signed-off-by:

Russell King <rmk+kernel@arm.linux.org.uk>

arch/arm/common/dmabounce.c

+10 −3

Original line number	Diff line number	Diff line
		@@ -281,9 +281,13 @@ map_single(struct device dev, void ptr, size_t size,
		ptr = buf->safe;

		dma_addr = buf->safe_dma_addr;
		}

		} else {
		/*
		* We don't need to sync the DMA buffer since
		* it was allocated via the coherent allocators.
		*/
		consistent_sync(ptr, size, dir);
		}

		return dma_addr;
		}
		@@ -397,7 +401,10 @@ sync_single(struct device *dev, dma_addr_t dma_addr, size_t size,
		default:
		BUG();
		}
		consistent_sync(buf->safe, size, dir);
		/*
		* No need to sync the safe buffer - it was allocated
		* via the coherent allocators.
		*/
		} else {
		consistent_sync(dma_to_virt(dev, dma_addr), size, dir);
		}

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