Mount root from SD card?

[Bernd Walter]

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.

> 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!

-- 
B.Walter <bernd at bwct.de> http://www.bwct.de
Modbus/TCP Ethernet I/O Baugruppen, ARM basierte FreeBSD Rechner uvm.