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

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Message-ID: <e3c34fb7-4881-3f49-b43b-1b07a8ab865d@microchip.com>
Date:   Tue, 29 May 2018 18:01:40 +0300
From:   Eugen Hristev <eugen.hristev@...rochip.com>
To:     Boris Brezillon <boris.brezillon@...tlin.com>,
        Peter Rosin <peda@...ntia.se>
CC:     Tudor Ambarus <tudor.ambarus@...rochip.com>,
        Nicolas Ferre <nicolas.ferre@...rochip.com>,
        Ludovic Desroches <ludovic.desroches@...rochip.com>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Marek Vasut <marek.vasut@...il.com>,
        Josh Wu <rainyfeeling@...look.com>,
        Cyrille Pitchen <cyrille.pitchen@...ev4u.fr>,
        <linux-kernel@...r.kernel.org>, <linux-mtd@...ts.infradead.org>,
        Richard Weinberger <richard@....at>,
        Brian Norris <computersforpeace@...il.com>,
        David Woodhouse <dwmw2@...radead.org>,
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH] mtd: nand: raw: atmel: add module param to avoid using
 dma

[...]


> 
> 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 ?

I have also received a suggestion to try to increase the porches in 
LCDC_LCDCFG3 .

>>
>>   >> [...]
> 
>