mirror of https://gitee.com/openkylin/linux.git
f1c089e319
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 <mika.westerberg@iki.fi> Acked-by: Russell King <rmk+kernel@arm.linux.org.uk> Acked-by: H Hartley Sweeten <hsweeten@visionengravers.com> Tested-by: Petr Stetiar <ynezz@true.cz> Signed-off-by: David S. Miller <davem@davemloft.net> |
||
|---|---|---|
| .. | ||
| Kconfig | ||
| Makefile | ||
| am79c961a.c | ||
| am79c961a.h | ||
| at91_ether.c | ||
| at91_ether.h | ||
| ep93xx_eth.c | ||
| ether1.c | ||
| ether1.h | ||
| ether3.c | ||
| ether3.h | ||
| etherh.c | ||
| ixp4xx_eth.c | ||
| ks8695net.c | ||
| ks8695net.h | ||
| w90p910_ether.c | ||