[PATCH] ARM: Ensure DMA-bounced buffers are properly written to RAM (5abc100e) · Commits · 戴 / test

When DMA bounce buffers were unmapped and the data was memcpy'd to the original buffer, we were not ensuring that the data was written to RAM. This means that there was the potential for page cache pages to have different cache states depending whether they've been bounced or not. Signed-off-by:

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

arch/arm/common/dmabounce.c

+14 −2

Original line number	Diff line number	Diff line
		@@ -302,12 +302,24 @@ unmap_single(struct device *dev, dma_addr_t dma_addr, size_t size,

		DO_STATS ( device_info->bounce_count++ );

		if ((dir == DMA_FROM_DEVICE) \|\|
		(dir == DMA_BIDIRECTIONAL)) {
		if (dir == DMA_FROM_DEVICE \|\| dir == DMA_BIDIRECTIONAL) {
		unsigned long ptr;

		dev_dbg(dev,
		"%s: copy back safe %p to unsafe %p size %d\n",
		__func__, buf->safe, buf->ptr, size);
		memcpy(buf->ptr, buf->safe, size);

		/*
		* DMA buffers must have the same cache properties
		* as if they were really used for DMA - which means
		* data must be written back to RAM. Note that
		* we don't use dmac_flush_range() here for the
		* bidirectional case because we know the cache
		* lines will be coherent with the data written.
		*/
		ptr = (unsigned long)buf->ptr;
		dmac_clean_range(ptr, ptr + size);
		}
		free_safe_buffer(device_info, buf);
		}

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