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

Andy Green andy at openmoko.com
Thu Oct 16 10:45:02 CEST 2008

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Somebody in the thread at some point said:
| The attached patch is for wider test and for review, not intended for
| the Om repo yet.

Understood... nice backport even if it doesn't impact GPS because there
will be a small power saving.

| 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++.

Well it should be in good shape if it's happy with those stresses.

| 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!

I think we should put it on stable given it needs wide testing for
something like GPS effect.  It would let people get the "unstable"
packages and really they can expect the odd problem there like broken
SD, but it would get it wider audience.

Since Jonas is looking at it if it is OK for him are you OK we just use it?

Thanks for taking the time to do this.

- -Andy
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