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Diffstat (limited to 'Documentation/arm')
| -rw-r--r-- | Documentation/arm/Samsung-S3C24XX/DMA.txt | 46 |
1 files changed, 46 insertions, 0 deletions
diff --git a/Documentation/arm/Samsung-S3C24XX/DMA.txt b/Documentation/arm/Samsung-S3C24XX/DMA.txt new file mode 100644 index 000000000000..37f4edcc5d87 --- /dev/null +++ b/Documentation/arm/Samsung-S3C24XX/DMA.txt @@ -0,0 +1,46 @@ + S3C2410 DMA + =========== + +Introduction +------------ + + 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 flexibilty for each cpu type and board, the + dma code can be given an 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 + orred 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 an complete ordering set. The routine will + copy the data, so the original can be discared with + __initdata. + + +Authour +------- + +Ben Dooks, +Copyright (c) 2007 Ben Dooks, Simtec Electronics +Licensed under the GPL v2 |