Re: [PATCH] mtd: nand: raw: atmel: add module param to avoid using dma

[Eugen Hristev]

On 29.05.2018 18:15, Boris Brezillon wrote:
> On Tue, 29 May 2018 18:01:40 +0300
> Eugen Hristev <eugen.hristev@xxxxxxxxxxxxx> wrote:
>
> > [...]
> >
> >
> > > I think you're missing something here. We use the DMA engine in memcpy
> > > mode (SRAM -> DRAM), not in device mode (dev -> DRAM or DRAM -> dev).
> > > So there's no dmas prop defined in the DT and there should not be.
> > >
> > > Regards,
> > >
> > > Boris
> > >    
> >
> > Ok, so the memcpy SRAM <-> DRAM will hog the transfer between DRAM and
> > LCD if my understanding is correct. That's the DMA that Peter wants to
> > disable with his patch ?
> >
> > Then we can then try to force NFC SRAM DMA channels to use just DDR port
> > 1 or 2 for memcpy ?
>
> You mean the dmaengine? According to "14.1.3 Master to Slave Access"
> that's already the case.
>
> Only DMAC0 can access the NFC SRAM and it's done through DMAC0:IF0,
> then access to DDR is going through port DDR port 1 (DMAC0:IF1) or 2
> (DMAC0:IF0).

If we can make NFC use port 1 only, then HLCDC could have two ports as 
master 8 & 9, maybe a better bandwidth.

> > I have also received a suggestion to try to increase the porches in
> > LCDC_LCDCFG3 .
>
> Yep, Nicolas suggested something similar. Peter, can you try that?