Re: [PATCH v2 2/2] media: imx: vdic: Introduce mem2mem VDI deinterlacer driver

[Marek Vasut <marex@denx.de>]

On 7/24/24 6:08 PM, Nicolas Dufresne wrote:
> Hi Marek,

Hi,

> Le mercredi 24 juillet 2024 à 02:19 +0200, Marek Vasut a écrit :
>> Introduce dedicated memory-to-memory IPUv3 VDI deinterlacer driver.
>> Currently the IPUv3 can operate VDI in DIRECT mode, from sensor to
>> memory. This only works for single stream, that is, one input from
>> one camera is deinterlaced on the fly with a helper buffer in DRAM
>> and the result is written into memory.
>>
>> The i.MX6Q/QP does support up to four analog cameras via two IPUv3
>> instances, each containing one VDI deinterlacer block. In order to
>> deinterlace all four streams from all four analog cameras live, it
>> is necessary to operate VDI in INDIRECT mode, where the interlaced
>> streams are written to buffers in memory, and then deinterlaced in
>> memory using VDI in INDIRECT memory-to-memory mode.
> 
> Just a quick design question. Is it possible to chain the deinterlacer and the
> csc-scaler ?

I think you could do that.

> If so, it would be much more efficient if all this could be
> combined into the existing m2m driver, since you could save a memory rountrip
> when needing to deinterlace, change the colorspace and possibly scale too.

The existing PRP/IC driver is similar to what this driver does, yes, but 
it uses a different DMA path , I believe it is IDMAC->PRP->IC->IDMAC . 
This driver uses IDMAC->VDI->IC->IDMAC . I am not convinced mixing the 
two paths into a single driver would be beneficial, but I am reasonably 
sure it would be very convoluted. Instead, this driver could be extended 
to do deinterlacing and scaling using the IC if that was needed. I think 
that would be the cleaner approach.