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S3C2410 DMA
The kernel provides an interface to manage DMA transfers
using the DMA channels in the CPU, so that the central
duty of managing channel mappings, and programming the
channel generators is in one place.
DMA Channel Ordering
Many of the range do not have connections for the DMA
channels to all sources, which means that some devices
have a restricted number of channels that can be used.
To allow flexibility for each CPU type and board, the
DMA code can be given a DMA ordering structure which
allows the order of channel search to be specified, as
well as allowing the prohibition of certain claims.
struct s3c24xx_dma_order has a list of channels, and
each channel within has a slot for a list of DMA
channel numbers. The slots are searched in order for
the presence of a DMA channel number with DMA_CH_VALID
or-ed in.
If the order has the flag DMA_CH_NEVER set, then after
checking the channel list, the system will return no
found channel, thus denying the request.
A board support file can call s3c24xx_dma_order_set()
to register a complete ordering set. The routine will
copy the data, so the original can be discarded with
Ben Dooks,
Copyright (c) 2007 Ben Dooks, Simtec Electronics
Licensed under the GPL v2