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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

Hi,

 

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 https://community.freescale.com/message/320532 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

24000

 

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?



Thanks



Alberto

 

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