On Thu, 10 Apr 2008 17:31:24 -0500 Ken.Fuchs@bench.com wrote:
Pierre Savary wrote:
I use a MMCplus 4GB on my design (with at91sam9260). It's wired with 4 bits.
The MCI controller on the AT91SAM926x family does not support MMCplus. There is no way to support a 4 bit bus, since the MCI controller supports only 1 bit to an MMC chip.
Untrue. The hardware interface is identical for 4-bit SD and 4-bit MMC. So if that part isn't working, it's because you either have a bug or because you lack 4-bit MMC support entirely in u-boot.
I know that the MCI controller can be used to access 1GB MMCplus chips, but I'm not sure it can be used to access MMCplus chips larger than that. There may be a special MMCplus command that will allow larger chips to be accessed. Try looking for it in your MMCplus chip's manual.
All compliant cards above 2 GB require special handling. They use a system identical to SDHC (except for the init). Check the specs (this part is publicly available) or the Linux code.
On Fri, 11 Apr 2008 10:26:52 +0200 "Pierre Savary" pierre.savary@kerlink.fr wrote:
Thanks a lot for your help. In fact it's not really important to support MMCplus, the main is to support MMC v4 where the extended CSD is introduced. Moreover, it's not really important if only one wire is used... I want only be able to read on a MMC 4Gb with my U-boot...
Just to avoid some more confusion, MMCplus is the marketing name of the full size MMC cards since version 4. So when discussing technical attributes, the MMCplus/MMCmobile distinction is not that useful. It's better to just call them v4. :)
Rgds