Re: [RFC] Generic DMA chaining APIs

[Tony Lindgren <tony@atomide.com>]

* Syed Mohammed, Khasim <x0khasim@ti.com> [070605 22:07]:
> Hi all:
> 
> I would like to port Generic DMA chaining API support from TI's 2430 DMA driver to our OMAP GIT DMA driver.
> 
> - Basically these APIs give flexibility for handling DMA chaining for drivers like McBSP (for audio), McSPI (for LCD), UART, etc. 
> 
> - Chaining is very important for drivers like Audio, LCD etc.
> 
> - Our current DMA driver on GIT does support APIs to enable /configure DMA logical channel chaining, but they have to be again used in client drivers to implement the queuing logic.
> 
> - Since there are multiple drivers in need of these kind of chaining support, it's preferable to implement them in a generic way so that all other drivers can leverage the code instead of creating a redundant copy in every driver.
> 
> A code snippet (from TI's DMA driver) is as shown below. Please do let me know if you find any issues with this kind of implementation/approach before I start (this week) this porting activity.
> 
> Thanks in advance.
> 
> APIs to be ported are:
> =====================
> omap_request_dma_chain
> omap_free_dma_chain
> omap_dma_chain_a_transfer
> omap_modify_dma_chain_params
> omap_start_dma_chain_transfers
> omap_stop_dma_chain_transfers
> 
> omap_dma_chain_status
> omap_get_dma_chain_index
> omap_get_dma_chain_dst_pos
> omap_get_dma_chain_src_pos

The new functions look OK to me.

Regards,

Tony