[PATCH] GTA01 - Use slow SD clock when GPS is on

Mike (mwester) mwester at dls.net
Mon Oct 20 07:16:30 CEST 2008

Attached is a patch to port Andy's "slow down the SD clock when the GPS
is on" technique to the GTA01.

I have no figures (how did the Om team come up with the measurements for
the GTA02 and GPS interference?).  However, anecdotal evidence very
strongly suggests that the SD clock on the GTA01 does adversely affect
the GPS on that device as well, so it seems to be reasonable to port
this patch back to the GTA01 as well.  (Specifically, my GTA01 can
reliably get a fix in a few minutes from startup when lying flat on my
desktop, booted from the SD card -- whereas previously getting a fix
required clear skies and an outdoor location if an SD card was even
installed.  That's only one data point, of course...)

NOTE!  As presented, this patch does not actually do anything(!) so as
to not change any user-visible behavior. The default value value for
sd_slow_ratio is 1 by default.  Distros or users that wish this to be
different will have to change the default, or do something like this at
boot time or before powering up the gps:

echo "8" >/sys/module/s3cmci/parameters/sd_slow_ratio

(Or, of course, a simple source code change to the default value is also

Mike (mwester)
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