Messages in this thread | | | Date | Thu, 02 Feb 2012 15:05:21 +0400 | From | Sergei Shtylyov <> | Subject | Re: RFC: usb: musb: Changes proposed for adding CPPI4.1 DMA |
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Hello.
On 02-02-2012 8:57, Gupta, Ajay Kumar wrote:
>>>>> As a next step to dma-engine based cppi4.1 driver implementation >>>>> this RFC has the overview of changes in the musb driver. >>>>> RFC on CPPI slave driver changes will follow next.
>>>>> Overview of changes in the musb driver >>>>> ======================================
>>>>> 1)Add a dma-engine.c file in the drivers/usb/musb folder >>>>> 2)This file will host the current musb dma APIs and translates them to >>>>> dmaengine APIs. >>>>> 3)This will help to keep the changes in drivers/usb/musb/musb* files >>>>> minimal and also to retain compatibility other DMA (Mentor etc.) >>>>> drivers which are yet to be moved to drivers/dma >>>>> 4)drivers/usb/musb/dma-engine.c, will wrap the dmaengine APIs to >>>>> make existing musb APIs compatible. >>>>> 5)drivers/usb/musb/dma-engine.c file will implement the filter >>>>> functions and also implement .dma_controller_create (allocates >>>>> & provides "dma_controller" object) and .dma_controller_delete >>>>> 6)CPPI4.1 DMA specific queue and buffer management will be internal >>>>> to slave CPPI DMA driver implementation.
>>>> You mean drivers/dma/ driver?
>>> yes.
>>>> I think you are forgotting that CPPI 4.1 MUSB >>>> has some registers controlling DMA/interrupts beside those of CPPI 4.1 >>>> controller and MUSB core itself. How do they fit in your scheme?
>>> We have been discussing on how to handle these in slave driver and
>> These certainly cannot be handled in the slave driver because the >> registers are different for every controller implementation and, the >> main thing, they don't belong to CPPI 4.1 as such.
> Felipe suggested to use device tree for differences in register maps > among different platforms.
I don't see how the device tree would magically help here.
> I do see issues in reading wrapper interrupt status register and then > calling musb_interrupt() [defined inside musb_core.c] from slave driver.
>>> would post our proposal in RFC for slave driver design. Do you have >>> any proposal?
>> I think this will need hooks from dma-engine.c to the glue layers. I >> was going to implement such in my version of MUSB CPPI 4.1 driver (in order >> to also support AM35x) but lacked time.
> That would mean a change in current drivers/dma API.
No, it doesn't. I'm proposing hooks from dma-engine.c which is situated in drivers/usb/musb/ if I got you right. It just means that the calls to dma-engine.c as MUSB DMA driver won't map to the calls to the DMA slave driver as directly as you've presented before.
> Ajay
>>> Regards, >>> Ajay
WBR, Sergei
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