I can't change the CPU frequency on the fly on mx28evk board, and in the Reference Manual document it tells us it is OK.
I have same problem here either. It seems like iMX28 Linux cpufreq driver
has serious bug.
The reference manual says
echo 392727 > /sys/devices/system/cpu/cpu0/cpufreq/scaling_setspeed
will change the CPU frequency, but the board just locks up.
(392727 should not be a supported frequency for iMX28 -
cat /sys/devices/system/cpu/cpu0/cpufreq/stats/time_in_state shows
261818, 360000 and 454736 as supported frequency. Anyway, setting
other than 454736 to scaling_setspeed causes lock-up).
My EVK is iMX28 EVK Rev.D, using Linux SDHC memory came with the EVK; uname -a shows
Linux freescale 2.6.31-855-ge067785 #1 Fri Sep 10 09:22:06 MDT 2010 armv5tejl GNU/Linux
Google search shows same issue was reported on forum back on Jul 2011.
Even though patch is provided from Freescale, it was reported it didn't fix the problem.
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