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author | Srikant Patnaik | 2015-01-13 15:08:24 +0530 |
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committer | Srikant Patnaik | 2015-01-13 15:08:24 +0530 |
commit | 97327692361306d1e6259021bc425e32832fdb50 (patch) | |
tree | fe9088f3248ec61e24f404f21b9793cb644b7f01 /Documentation/arm/Samsung-S3C24XX/DMA.txt | |
parent | 2d05a8f663478a44e088d122e0d62109bbc801d0 (diff) | |
parent | a3a8b90b61e21be3dde9101c4e86c881e0f06210 (diff) | |
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dirty fix to merging
Diffstat (limited to 'Documentation/arm/Samsung-S3C24XX/DMA.txt')
-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 00000000..3ed82383 --- /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 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 + __initdata. + + +Authour +------- + +Ben Dooks, +Copyright (c) 2007 Ben Dooks, Simtec Electronics +Licensed under the GPL v2 |