General Purpose DMA Engine Framework for FreeBSD (GPDMA)

The aim of this project is to provide a generic, flexible framework for initiating and controlling DMA transfers using General Purpose DMA engines, found in most of embedded SoCs - along with tests and documentation. There are analogous frameworks for NetBSD (dmover(4)) and Solaris (ddi_dmae(9F)), but they are not well suited for embedded targets and don't offer all required features.

1. Design and implement kobj-based API for DMA engines drivers, along with respective manual pages. API would include operations for programming DMA channels, starting/stopping transfers and completion notification to upper layer via apporiate callbacks. There should be possibility to express even complex DMA transfers - with support for memory filling, XOR engines, reading/writing on memory mapped FIFOs, etc. Upper layer should also have information about transfer types supported by particular DMA engine and it's limitations.
2. Implement respective API for upper layer - kernel and device drivers and, of course, document it in manual pages. Introduce new type of resource - SYS_RES_DMA - describing DMA channels.
3. Provide an example implementation of DMA engine driver using our new framework - edma(4) on TI DaVinci (DM644x) and optionally idma(4) on Marvell 88F6xxx (SheevaPlug).
4. Make some parts of kernel use DMA engine, if available (memcpy, bzero, etc).
5. Convert example device driver to use our new framework - most likely dvmmc(4) on TI DaVinci.
6. Write character device driver (/dev/dma?) implementig some ioctl() calls to allow userspace applications benefit from hardware memory copying/filling.
7. Implement unit tests to check whether all possible transfer types work correctly.
8. Implement regression tests to verify correctness of operation in stress environments.
9. Put all above in form suitable for commiting.

RafalJaworowski

• DMA engine driver API
• Kernel API for GPDMA
• GPDMA character device

• FreeBSD/DaVinci port
• dmover(4) on NetBSD
• ddi_dmae(9F) on Solaris
• DM6446 documents
• Project P4 branch