[NATTY SRU Patch 0/1] mmc: Added quirks for Ricoh 1180:e823 lower base clock frequency

[Manoj Iyer]

Please consider the following SRU for Natty, it fixes Ricoh SD/MMC card
reader which fails to read certain types of MMC/SD Cards. Please note that
this patch should be applied on top of the patch to Ricoh mmc already SRUed
for natty and maverick. http://patchwork.ozlabs.org/patch/98056/ 

SRU JUSTIFICATION
================

EFFECT
======
Ricoh 1180:e823 does not recognize certain types of SD/MMC cards.
- Buffalo SD 512MB
  dmesg: I/O error, dev mmcblk0, sector xxx
- Kingston SD 2GB
  dmesg: I/O error, dev mmcblk0, sector xxx
- Patriot Micro SDHC
  dmesg: I/O error, dev mmcblk0, sector xxx.

FIX
===
Lowering the SD base clock frequency from 200Mhz to 50Mhz fixes 
this issue. This solution was suggest by Koji Matsumuro, Ricoh Company, Ltd.

TEST
====
Performance test results with various MMC and SD cards were posted 
to https://lkml.org/lkml/2011/7/11/381 and also part of the results 
attached to this bug.


The following changes since commit 84aa86ba6a3f2331f1cfbab9b6def072ac1dee37:

  mmc: Added quirks for Ricoh 1180:e823 lower base clock frequency (2011-07-25 11:19:53 -0500)

are available in the git repository at:
   git://kernel.ubuntu.com/manjo/ubuntu-natty.git lp773524