Hello. On 01/13/2012 01:40 PM, Gupta, Ajay Kumar wrote:
CPPI4.1 (Communication Port Programming Interface) is a TI specific DMA controller used in multiple TI platform such as AM33x, DA8x, AM35x, TI81x. The DMA engine is mainly used by musb controller on above platform.
There are (at least out of tree) platforms using CPPI 4.1 for Ethernet.
Earlier version of the driver was submitted by Sergei Shtylyov at [1] but was not merged due to disagreement on the location of driver in kernel.
To be precise, TI requested pulling out already queued (to arch/arm/common/) CPPI 4.1 driver from RMK's patch system without even notifying me. At least that was RMK's version...
Refer the discussions at [1] for more details.
[1] http://marc.info/?l=linux-usb&m=125087318308323
Unfortunately, that's not all of the discussion of interest.
The new implementation of the CPPI4.1 DMA slave driver will be in the drivers/dma folder, complying to dmaengine framework.
Has there been any work in this direction done yet?
It would involve changes in existing musb driver also for which current plan is to maintain the compatibility of non-CPPI4.1 DMA in musb driver.
I didn't quite understand this part...
The task is planned to be spitted into below subtasks.
(1) Post RFC on the API details, changes envisaged in musb driver and other challenges
First of all, I foresee changes in drivers/dma/ to cope with the entity in CPPI 4.1 called the queue manager (there's also buffer manager but it wasn't implemented on DA8xx, so I didn't design any API for it).
(2) Implement and post RFC for the CPPI4.1 DMA driver and changes needed in musb driver.
Let me know if you have any thoughts/comments on this.
Regards, Ajay
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