failed mount root on pi

[Oleksandr Tymoshenko]

On 2/18/2013 8:21 AM, Brett Wynkoop wrote:
> Greeting-
>
> I built a new kernel from head as of yesterday.  The new kernel boots
> fine, but it can not seem to mount root.
>
> I am wondering if anyone else is having the same issue and what may
> have changed to make it impossible for the Pi to mount the SD card.
>
There was a problem with SDHCI driver: card capabilities read from the 
card were
incomplete. Usually it was 1-bit bus instead of 4-bit bus or no high 
speed timing
for cards that support high speed timing. It worked although not at maximum
performance. With this problem gone new bug revealed - some cards stop
responding when SDHCI is switched to high speed timing mode. Me and Ian
looking into it. Meanwhile try adding following string to /boot/loader.rc on
UFS partition:

set hw.bcm2835.sdhci.hs=0