Re: [PATCH] ARM: OMAP2: Camera: Add OMAP2 24xx camera driver.

[Sakari Ailus <sakari.ailus@nokia.com>]

ext Syed Mohammed, Khasim wrote:
> I am yet to review this patch completely. One immediate topic that I
> want to bring up is about DMA files. In Jian's code to David and Komal
> he had DMA driver integrated into camera driver and David moved the DMA
> part to new file. Which according to me was an OK one, but in your patch
> set I see around 3 DMA related files. I really don't see a necessity for
> this split. 
> 
> If you really want to clean up the DMA part of it then its better to
> upgrade the dma.c file for OMAP2, the CAM_DMA and system_DMA are same.
> Why not add this functionality there? Or use the existing DMA
> functionality instead of duplicating the code.
> 
> Also, looking at the future Camera work for 3430 I feel this DMA
> framework is definitely going totally different (FYI there is no
> integrated CAM DMA in ISP). We have to use MMU here and we are looking
> at adopting Trilok's and DOYU-san's MMU framework.

I haven't looked at the 3430 spec yet, but the MMU should be used on 
2420 as well. Is it different on 3430? The current allocation of 
memory-mapped buffers is a hack...

> Can you please give some insight into this DMA split?

I did the DMA split to reduce the mess. I also think the new interface 
offered by the DMA code is better. DMA is split to scatter-gather DMA, 
individual DMA channels and DMA hardware handling. Accesses to different 
logical parts are fairly clearly visible (e.g. container_of stuff). And 
it's out of the main driver. The splitting into files could be of course 
different, but I have to say like some things in Java. ;)

But indeed if there's a general DMA framework that could be used, then I 
suppose that's the way to go eventually.

-- 
Sakari Ailus
sakari.ailus@nokia.com