[PATCH] MTD: atmel_nand: Add DMA support to access Nandflash

On 01/18/2011 09:15 AM, Ryan Mallon wrote:

On 01/17/2011 08:20 PM, Hong Xu wrote:

quoted

Some SAM9 chips have the ability to perform DMA between CPU and SMC controller.
This patch adds DMA support for SAM9RL, SAM9G45, SSAM9G46,AM9M10, SAM9M11.

I'm trying to patch this into a 2.6.33 kernel running on a custom
SAM9G45 based board, but I get a failure requesting the DMA channel:

root at snapper:~$ 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?

Also, I think you want to add the following for the atmel_nand Kconfig:
  select AT_HDMAC

or make the DMA parts of the driver ifdef CONFIG_AT_HDMAC (if the above
won't work for some reason) since you will get build errors on the
dmaengine functions otherwise.

~Ryan

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