From: Mika Westerberg Date: Sat, 11 Jun 2011 08:39:58 +0000 (+0000) Subject: net: ep93xx_eth: fix DMA API violations X-Git-Tag: v3.0-rc3~13^2~2 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=f1c089e3192f1afdfa76226dc38ef81b08ac810d;p=pandora-kernel.git net: ep93xx_eth: fix DMA API violations Russell King said: > > So, to summarize what its doing: > > 1. It allocates buffers for rx and tx. > 2. It maps them with dma_map_single(). > This transfers ownership of the buffer to the DMA device. > 3. In ep93xx_xmit, > 3a. It copies the data into the buffer with skb_copy_and_csum_dev() > This violates the DMA buffer ownership rules - the CPU should > not be writing to this buffer while it is (in principle) owned > by the DMA device. > 3b. It then calls dma_sync_single_for_cpu() for the buffer. > This transfers ownership of the buffer to the CPU, which surely > is the wrong direction. > 4. In ep93xx_rx, > 4a. It calls dma_sync_single_for_cpu() for the buffer. > This at least transfers the DMA buffer ownership to the CPU > before the CPU reads the buffer > 4b. It then uses skb_copy_to_linear_data() to copy the data out. > At no point does it transfer ownership back to the DMA device. > 5. When the driver is removed, it dma_unmap_single()'s the buffer. > This transfers ownership of the buffer to the CPU. > 6. It frees the buffer. > > While it may work on ep93xx, it's not respecting the DMA API rules, > and with DMA debugging enabled it will probably encounter quite a few > warnings. This patch fixes these violations. Signed-off-by: Mika Westerberg Acked-by: Russell King Acked-by: H Hartley Sweeten Tested-by: Petr Stetiar Signed-off-by: David S. Miller --- Reading git-diff-tree failed