linux-kernel - Re: [PATCH] MTD: atmel_nand: Add DMA support to access Nandflash

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Date:	Tue, 18 Jan 2011 15:44:58 +1300
From:	Ryan Mallon <ryan@...ewatersys.com>
To:	"Xu, Hong" <Hong.Xu@...el.com>
CC:	linux-kernel@...r.kernel.org, linux-mtd@...ts.infradead.org,
	linux-arm-kernel@...ts.infradead.org, jamie@...ieiles.com,
	jacmet@...site.dk, Nicolas Ferre <nicolas.ferre@...el.com>
Subject: Re: [PATCH] MTD: atmel_nand: Add DMA support to access Nandflash

On 01/18/2011 02:43 PM, Xu, Hong wrote:
> Hi Ryan,
>> -----Original Message-----
>> From: Ryan Mallon [mailto:ryan@...ewatersys.com]
>> Sent: Tuesday, January 18, 2011 6:42 AM
>> To: Xu, Hong
>> Cc: linux-mtd@...ts.infradead.org; linux-arm-kernel@...ts.infradead.org;
>> linux-kernel@...r.kernel.org; jamie@...ieiles.com; jacmet@...site.dk;
>> Ferre, Nicolas
>> Subject: Re: [PATCH] MTD: atmel_nand: Add DMA support to access Nandflash
>>
>> root@...pper:~$ dmesg | grep -i dma
>> [    0.850000] atmel_nand atmel_nand: Failed to request DMA channel
>> [    0.860000] atmel_nand atmel_nand: No DMA support for NAND access.
>> [    1.530000] at_hdmac at_hdmac: Atmel AHB DMA Controller ( cpy slave ),
>> 8 channels
>>
>>
>> It looks like the registration for the DMA controller happens after the
>> NAND driver probe and so the request is failing. I had a quick look, but
>> I can't see anything that would change this in more recent kernels. Any
>> ideas?
>>
> You got the point. A [Git Pull] has been sent, see
> http://article.gmane.org/gmane.linux.kernel/1088240/match=dmaengine+update
> 
> In this patch, subsys_initcall will be used so DMA engine will be initialized before NAND driver.
> Thanks.

Thanks, that fixed it.

I have tried this under 2.6.33 on a custom SAM9G45 based board with a
512MiB NAND part, with 2kB pages and 128kB blocks using both raw MTD
access and the YAFFS2 filesystem and it appears to work correctly.

Tested-by: Ryan Mallon <ryan@...ewatersys.com>

Can you please update for the changes I suggested.

Thanks,
~Ryan

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