[PATCH] *not for git* GTA01 - stop the SD card clock when idle

Mike (mwester) mwester at dls.net
Thu Oct 16 08:12:03 CEST 2008

The attached patch is for wider test and for review, not intended for
the Om repo yet.

It's not been checked to ensure it adheres to proper coding style, and
it's missing a Signed-off-by line -- but that's the least of the worries
with this patch.  Please try it, but please don't try it with an SD card
that has anything on it that you want to keep!

This implements two of the "Andy Glamo SD" features -- the clock to the
SD card is disabled when the card is not transferring data, and you can
set the maximum SD clock speed on the kernel command line.  Note that
the max SD clock speed is 16.625 MHz on the GTA01.

I've tested with a 512MB Sandisk SD card, it suspends and resumes, and
completed a quick pass with bonnie++.

The goal of this, of course, is to see if it changes the GPS performance
at all.  I've done no tests in that area whatsoever, so that would be a
really good bit of information to have.  In particular, if it is
determined that limiting the max speed has a positive effect for GPS
performace, then I'll implement Andy's
automatic-slowdown-when-gps-is-powered-up feature -- but if it doesn't
then I'll forgo that effort (since the limited flash space on the GTA01
will force most everyone to use a rootfs on SD, it would be a shame to
slow performance if it had no benefit, of course!).

I'll send in a properly formatted and signed off version once I get a
little feedback.  Happy GPSing!

Mike (mwester)
-------------- next part --------------
An embedded and charset-unspecified text was scrubbed...
Name: gta01_stop_SD_clock_when_idle_TEST.patch
Url: http://lists.openmoko.org/pipermail/openmoko-kernel/attachments/20081016/9f0210d8/attachment-0001.txt 

More information about the openmoko-kernel mailing list