[U-Boot-Users] drivers MMCplus for at91sam9x

[Ken.Fuchs at bench.com]

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.  The MCI will
support a 4 bit SD chip, but I don't think it can be tricked
into working with a 4 bit MMC chip (at least not via software
alone).

The only reasonable solution is switching to a processor that
has MMCplus support.  Maybe Atmel has been working on one?

> Currently U-boot (1.1.5) can't detect correctly the MMC and 
> so I can't read my Linux kernel Image on the ext3 part of this
> MMC. If I use MMC 1GB, it works.

Did you add MMCplus commands to the MCI U-Boot driver?  You can
do this to the extent that these changes do not require the MCI
controller to be MMCplus compliant.  (The MCI U-Boot driver I'm
aware of contains no MMCplus support.)

I suggest that you use the u-boot sources available via git.
You will get very little support (if any) from the U-Boot ML for
two reasons:

1) U-Boot 1.1.5 is extremely old and no one on the list is
   interested in supporting it.

2) The version of U-Boot 1.1.5 you are using almost certainly
   has an Atmel patch applied to it that was never accepted
   into the "official" U-Boot tree.

However, ...

It appears that someone is working on the AT91SAM9260 within the
official U-Boot (git) tree, since the ./include/configs/at91sam9260ek.h
file is there.  Other file structures like ./cpu/arm926ejs/* seem to be
missing some drivers and other support files.  I know that the
AT91SAM926x specific U-Boot files were never an official part of
U-Boot, but that appears to be changing.  It is my understanding
that the AT91SAM926x support is being completely reworked and
integrated with the AT91CAP9 code that has been present in git
for over a month already.  The AT91CAP9 and AT91SAM926x are very
similar and should share a lot of code.

Even if the AT91SAM9260 is not quite ready, the AT91CAP9 code
should provide the basis of a current U-Boot for the AT91SAM926x
family.

> Somebody have already use it? Or somebody have already implemented
> the ext_csd and high capacity with MMC on another platform?

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.

Sincerely,

Ken Fuchs

> -----Original Message-----
> From: u-boot-users-bounces at lists.sourceforge.net 
> [mailto:u-boot-users-bounces at lists.sourceforge.net] On Behalf 
> Of Pierre Savary
> Sent: Tuesday, April 08, 2008 09:32
> To: u-boot-users at lists.sourceforge.net
> Cc: 'Pierre Ossman'
> Subject: [U-Boot-Users] drivers MMCplus for at91sam9x
> 
> 
> Hi,
> I use a MMCplus 4GB on my design (with at91sam9260). It's 
> wired with 4 bits.
> Currently U-boot (1.1.5) can't detect correctly the MMC and 
> so I can't read
> my Linux kernel Image on the ext3 part of this MMC. If I use 
> MMC 1GB, it
> works.
> Somebody have already use it? Or somebody have already implemented the
> ext_csd and high capacity with MMC on another platform?
> I need help. Thanks in advance to help me.
> 
> Regards,
> 
> Pierre
> 
> 
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