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:
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?