I am trying to implement a large data DMA from GPMC area. The data volume is more than 1 MB.
This how I setup DMA in my kernel driver:
// Setting parameters
omap_set_dma_transfer_params(ch_out,
OMAP_DMA_DATA_TYPE_S32, // element size (4 Bytes)
elements, // # elements in frame
frames, // # frames in block
OMAP_DMA_SYNC_FRAME, // sync_mode
0, OMAP_DMA_SRC_SYNC);
omap_set_dma_src_params(ch_out, 0, OMAP_DMA_AMODE_POST_INC,
src_buf_phys, // source memory address
0,
0);
omap_set_dma_dest_params(ch_out, 0, OMAP_DMA_AMODE_POST_INC,
dest_buf_phys, // dest memory address
sizeof(UInt32), // offset between elements in dest memory
elements); // offset between frames in dest memory
Everything works while number of frames = 1 (up to 64K words).
Whenever I make frames more than 1:
-
If sync_mode is OMAP_DMA_SYNC_FRAME - DMA stops after 1st frame
-
If I am using OMAP_DMA_SYNC_BLOCK synchronization – I am getting a run-time error (“SDMA2EDMA: Line:202 : Param 'sync_mode' out of range”).
If I am reading manual right (AM335x Sitara Technical Reference Manual, page 1483) it also says:
“ABC-synchronized transfers are not directly supported. But can be logically achieved by chaining between multiple AB-synchronized transfers.”
Does it mean that I have to implement this loop in my kernel driver?
This will definitely work, but also will significantly decrease the performance of the system
Thanks
Leonid.
