Messages in this thread | | | Date | Fri, 13 Jan 2012 23:41:13 +0300 | From | Sergei Shtylyov <> | Subject | Re: RFC: usb: musb: Adding CPPI4.1 DMA driver under drivers/dma |
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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
WBR, Sergei
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