Mount root from SD card?

[Krassimir Slavchev]

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M. Warner Losh wrote:
> In message: <20090122235712.GO50103 at cicely7.cicely.de>
>             Bernd Walter <ticso at cicely7.cicely.de> writes:
> : On Thu, Jan 22, 2009 at 04:26:33PM -0700, M. Warner Losh wrote:
> : > 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...
> : 
> : I already noticed his work with great pleasure.
> : 
> : > : > 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...
> : 
> : It never worked - I tried it a while back and had interesting results,
> : but it wasn't stable, which I asumed to be my bad knowledge on how this
> : should be implemented correctly.
> : Thanks to mav@ we have other controllers working and can test the
> : sdmmc part unrelated from mci.
> : Nevertheless: multiblock is the real speed issue.
> : My speed tests were very impressive, but because of mci problems data
> : were corrupted of course.
> 
> I'll see if I can find an hour or two to look into the proper reset of
> the mci fifos after use...  I'd also like to get 4-bit working too...

I have added some debug info with 4-bit mode enabled:

http://mnemonic.bulinfo.net/~krassi/ARM/sd.dump3

> 
> Right now I'm only getting ~900kB/s (890-919) and we can do much
> better, no?
> 
> Warner
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