On 12/18/2012 08:16 AM, Matej Kupljen wrote:
Dear Sergey and Jeff,
I have a board based on AT91SAM9263, with the CF connected to
the EBI0 and I am using the pata-at91.c driver.
My question is, can I use DMA (MWDMA and/or UDMA) for the CF card,
of course, if I add support to the driver?
Basically, the question is, can we use the HDMAC (DMA controller)
to support the DMA transfers?
Please note that the DMARQ and DMACK are connected from CF to SoC.
I've been looking for this in the documentation, and I cannot find the
answer. Considering that the SAM9263 is considered legacy, I have
checked the documentation for AT91SAM9R/RL and AT91SAM9G and I couldn't
find the answer there either.
Can you answer this question, please?
If not, to whom I should send it?
Thank you and Best Regards,
Matej Kupljen
Hi,
In the future could you please consider sending your questions to a
proper kernel mail list cc-ing authors/maintainers if necessary.
As you noted, driver pata-at91 does not have dma support. This is
because originally it has been developed for a board based on
at91sam9260 chip which has no dma engine. More recent at91 chips
(including at91sam9263) do have dma engines. It should be possible to
add dma support to pata-at91 driver and use dma transfers for CF.
A couple of notes regarding at91sam9263:
1. DMA driver
IIRC at91sam9263 chip has a different dma engine than all the other
chips of at91 family. More recent chips have HDMAC:
drivers/dma/at_hdmac.c while at91sam9263 has DWDMA: drivers/dma/dw_dmac.c
2. Size of dma transfers
IIRC there is a problem with dma engine on at91sam9263 chip: it has
significantly reduced block size for transfers. This leads into a fairly
small max transfer size in a single block transfer. As a result, it
might not be practical to use this particular dma engine for CF.
Thanks,
Sergey
--
To unsubscribe from this list: send the line "unsubscribe linux-ide" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
