OLPC XO-1 sdhci regression

[Andres Salomon <dilinger@queued.net>]

Hi Pierre,

With the current Linus git tree, the sdhci driver fails to find the partition
table on cards during bootup on OLPC XO-1 machines.  This makes booting off of
SD impossible.  The errors go something like this:

 mmcblk0:
mmc0: Timeout waiting for hardware interrupt.
mmcblk0: error -110 sending stop command
end_request: I/O error, dev mmcblk0, sector 0
Buffer I/O error on device mmcblk0, logical block 0
[repeat a bunch of times]
  unable to read partition table

No oopses or anything, the SD controller just fails to read the partition
table off the card.

I bisected a bit, and that led me to this commit:

 commit e809517f6fa5803a5a1cd56026f0e2190fc13d5c
 Author: Pierre Ossman <drzeus@drzeus.cx>
 Date:   Fri Jul 25 01:09:08 2008 +0200

     sdhci: let the controller wait for busy state to end
    
     The sdhci controllers can interrupt us when the busy state from the
     card has ended, saving CPU cycles and power.
    
     Signed-off-by: Pierre Ossman <drzeus@drzeus.cx>

Reverting that commit allows the driver to read the partition table.