Forum Post: RE: Beaglebone Black DMA support in uboot

Thanks for the info.

Are there some guidelines on how to use DMA with the eMMC?

The TRM says the MMC controller can work in DMA slave mode and a request is issued if the following conditions are met:

-The SD_CMD[0] DE bit is set to 1 to trigger the initial DMA request (the write must be done when
running the data transfer command).
-A command was emitted on the SD_cmd line

My questions more specifically is:

How do I set up the DMA to receive the requests (channels, events, etc.)?
How do I set up the MMC to trigger the DMA request? (specific changes from a normal data read)

Thanks

Michal