Hi Chris,
I've been using the "optional" drivers for SDHC and atheros wireless on
our DM355 product. But there are issues with it. In order to get the
drivers to behave with the TI codecs I've had to turn off DMA.
I believe this is related to the errata on the SDIO DMA slots issued by Ti:
2.1.4 SD/SDIO card: How to Read M bytes (M=1, 2, 3) from SD or SDIO card
Direction: Read from SD or SDIO
Data size: 32*N+M byte (where M=1, 2, 3 and N=0, 1, 2, 3,...) FIFO
size is 32 bytes (ACCWD (FIFOCTL
[4:3] = 0), FIFO trigger level is 256-bits (FIFOLEV (MMCFIFOCTL
[2]) =1)
Reading from SD or SDIO when FIFO Trigger Level FIFOLEV is 256
bits causes the
DRRDY(MMCST0[10]) bit not to be set for the last M bytes of the
above data size equation and therefore
the DMA read event and CPU interrupt for RRDY(MMCST0[10]) are not
getting asserted, but the data in
FIFO is correct.
There are two possible methods to work around this limitation.
1. Include SD status checking and/or SD interrupt enable for
TRNDNE (MMCST0 [12]) or DATDNE
(MMCST0 [0])
2. Use 128-bit FIFO trigger level (i.e. FIFOLEV (MMCFIFOCTL [2])
=0), since this is only a problem when
FIFOLEV is 256 bits.
Note:
In any case, the drivers should be available as loadable kernel modules
with the latest distribution. They are also available on the cardaccess
web site:
http://www.cardaccess-inc.com/support/wlan/index.php?a=wlan_burt --
along with directions on how to build them into your kernel.
The drivers will replace the original kernel drivers and you shouldn't
have a problem using SDHC... as long as you turn off DMA. Use the
no_dma=1 parameter:
insmod sdio_davinci_hcd.ko no_dma=1
Good luck,
Steve
Chris Stillson wrote:
Has anyone actually used sdhc card on a dm355? The docs say it isn't
supported, but I'm wondering if it can be worked around.
Chris
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