Comment 40 for bug 773524

Manoj Iyer (manjo) wrote :

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.