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

[Nicolas Dufresne]

Le lundi 29 juillet 2024 à 04:16 +0200, Marek Vasut a écrit :
> 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.

Not that I only meant to ask if there was a path to combine
CSC/Scaling/Deinterlacing without a memory rountrip. If a rountrip is needed
anyway, I would rather make separate video nodes, and leave it to userspace to
deal with. Though, if we can avoid it, a combined driver should be highly
beneficial.

cheers,
Nicolas