Mount root from SD card?

[M. Warner Losh]

In message: <20090122230647.GN50103 at cicely7.cicely.de>
            Bernd Walter <ticso at cicely7.cicely.de> writes:
: On Thu, Jan 22, 2009 at 03:57:41PM -0700, M. Warner Losh wrote:
: > In message: <20090122180518.GK50103 at cicely7.cicely.de>
: >             Bernd Walter <ticso at cicely7.cicely.de> writes:
: > : On Thu, Jan 22, 2009 at 08:02:14PM +0200, Alexander Motin wrote:
: > : > Bernd Walter wrote:
: > : > >As another point:
: > : > >Is it possible to support SHDC with mci some day, or is there a special
: > : > >hardware requirement for SDHC?
: > : > 
: > : > SDHC (SD High Capacity) has just a different data addressing scheme (in 
: > : > 512bytes blocks instead of bytes). There is no special hardware 
: > : > requirements, only minor initialization differences. With present 
: > : > mmc/mmcsd modules SDHC should work fine on any controller.
: > : 
: > : Good news - thank you for clearification.
: > 
: > Now all we need to do is to enhance the boot blocks to be able to boot
: > off the SDHC cards :)
: 
: Yes, but since you wrote code to store the kernel inside SPI-flash
: there is a useable workaround available ;-)
: Full loader support would be more interesting than SDHC in boot code
: anyway.

Raj@ did some interesting work in this area for the marvel port...

: > BTW, I found and fixed the bug (at least I think so).  We were
: > assuming that all transfers were 512 bytes long.  The newly used 16
: > and 64 byte transfers broke that assumption, which is why things broke
: > after Alexander's latest commits.  There's still a small chance that
: > there's something borked in the byte swapping code, but I kinda doubt
: > it since I was able to mount root.
: > 
: > svn commit r187603 is the fix.
: 
: Great!

Well, it doesn't work in 4-bit bus mode.  Of course, I'm not sure it
ever worked in 4-bit bus mode...

Warner