linux/drivers/net/arm
Mika Westerberg f1c089e319 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 <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>
2011-06-11 16:25:16 -07:00
..
am79c961a.c NET: am79c961: fix assembler warnings 2011-06-11 15:56:01 -07:00
am79c961a.h am79c961a: Use net_device_stats from struct net_device 2010-08-17 02:32:55 -07:00
at91_ether.c net: trans_start cleanups 2010-05-10 05:01:31 -07:00
at91_ether.h
ep93xx_eth.c net: ep93xx_eth: fix DMA API violations 2011-06-11 16:25:16 -07:00
ether1.c ether1: Use net_device_stats from struct net_device 2010-08-19 00:12:38 -07:00
ether1.h ether1: Use net_device_stats from struct net_device 2010-08-19 00:12:38 -07:00
ether3.c ether3: Use net_device_stats from struct net_device 2010-08-19 00:12:38 -07:00
ether3.h ether3: Use net_device_stats from struct net_device 2010-08-19 00:12:38 -07:00
etherh.c Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next-2.6 2011-05-20 13:43:21 -07:00
ixp4xx_eth.c ptp: Added a clock driver for the IXP46x. 2011-05-23 13:10:19 -07:00
Kconfig
ks8695net.c ethtool: cosmetic: Use ethtool ethtool_cmd_speed API 2011-04-29 14:03:01 -07:00
ks8695net.h
Makefile
w90p910_ether.c drivers/net: normalize TX_TIMEOUT 2010-11-09 09:17:56 -08:00