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Subject: Re: [PATCH] mtd: nand: raw: atmel: add module param to avoid using
 dma
To:     Boris Brezillon <boris.brezillon@bootlin.com>
CC:     Peter Rosin <peda@axentia.se>,
        Tudor Ambarus <tudor.ambarus@microchip.com>,
        Nicolas Ferre <nicolas.ferre@microchip.com>,
        Ludovic Desroches <ludovic.desroches@microchip.com>,
        Alexandre Belloni <alexandre.belloni@bootlin.com>,
        Marek Vasut <marek.vasut@gmail.com>,
        Josh Wu <rainyfeeling@outlook.com>,
        Cyrille Pitchen <cyrille.pitchen@wedev4u.fr>,
        <linux-kernel@vger.kernel.org>, <linux-mtd@lists.infradead.org>,
        Richard Weinberger <richard@nod.at>,
        Brian Norris <computersforpeace@gmail.com>,
        David Woodhouse <dwmw2@infradead.org>,
        <linux-arm-kernel@lists.infradead.org>
References: <20180329131054.22506-1-peda@axentia.se>
 <20180329153322.5e2fc1e7@bbrezillon>
 <ed87cf13-a69a-6115-f0a8-5f51c4957d1d@axentia.se>
 <20180329154416.5c1a0013@bbrezillon>
 <b740406a-e91c-67ad-24a3-cbdbe259d00d@axentia.se>
 <20180402142249.7e076a64@bbrezillon>
 <e0d9bd59-8031-e387-676e-dc5811170a0c@axentia.se>
 <20180402212843.164d5d21@bbrezillon> <20180402222020.1d344c14@bbrezillon>
 <d7e6f78d-b57b-4d0f-c07c-ca6c1930cd51@axentia.se>
 <20180403091813.5fb5c18c@bbrezillon>
 <d0afd431-6e51-a9b7-c103-ecf1f6e07c2e@axentia.se>
 <959d826d-1a98-ca22-acee-a4548427fcd3@microchip.com>
 <a25ca617-d3da-d401-1ba9-8e5887f8a8e5@microchip.com>
 <024079cb-77ad-9c48-e370-e6e8f2de171b@axentia.se>
 <9c496531-f7b6-4b9d-dd51-0bfb68ead303@axentia.se>
 <c3cc1894-2d7d-93b6-a9de-ed9ca4564ae9@axentia.se>
 <19d68279-072e-7646-6fdd-8649578229ea@microchip.com>
 <20180529164911.29820e07@bbrezillon>
 <e3c34fb7-4881-3f49-b43b-1b07a8ab865d@microchip.com>
 <20180529171555.19dd723f@bbrezillon>
From:   Eugen Hristev <eugen.hristev@microchip.com>
Message-ID: <1affd186-7f78-8bb0-050e-da82143c2982@microchip.com>
Date:   Tue, 29 May 2018 18:21:40 +0300
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On 29.05.2018 18:15, Boris Brezillon wrote:
> On Tue, 29 May 2018 18:01:40 +0300
> Eugen Hristev <eugen.hristev@microchip.com> 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?
>