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imx233 hang changing freq from 24MHz to 261MHz

Question asked by Alberto Biancalana on Mar 25, 2013
Latest reply on Apr 3, 2013 by Alberto Biancalana
Branched to a new discussion



I'm working on power consumption of an imx233 based device, to test low frequency profiles.

I use 2.6.31 Kernel supplied for im233 by LTIB (1005).

I have another thread open regarding power consumption and USB disable and this problem stop me to proceed in the work.


Here the problem:

By simply disabling LCDIF through display unblank, and without activating USB host, I can select the 24Mhz profile with:


echo 4 > /class /graphics/fb0/blank (LCDIF disable)

echo 24000 > /sys/devices/system/cpu/cpu0/cpufreq/scaling_setspeed (cpu speed at 24Mhz)


and this should be true because:


cat /sys/devices/system/cpu/cpu0/cpufreq/cpuinfo_cur_freq



and I notice a lower consumption (only about 8mA starting from 260Mhz, I thought more).


The problem is that coming back to 260Mhz with:


echo 261818 > /sys/devices/system/cpu/cpu0/cpufreq/scaling_setspeed


the system hangs.


No messages, debug console out of control, system dead.


Note that I set the speed back to 261Mhz with LCDIF still unactive, with the intention to unblank only when at high speed with  echo 0 > /class /graphics/fb0/blank (LCDIF disable) .

No application running, simply linux console.

Am I doing something wrong or there is a problem in this release for this?