imx233 hang changing freq from 24MHz to 261MHz

[whitewool]

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

[GraceH · Accepted solution]

Hi Alberto,

We have MX28 patch to fix the hang-up when change frequency. But unfortunately, there is no patch for MX233.

I attached patches for MX28 for your reference.  The ideas are same, that is all DMA operation need be suspended when change EMI frequency.  The fix is included in MX28 2.6.35.1.1.0 release.

Regards,

Grace

[whitewool]

Thanks Grace,

just downloaded.

I'll take a look and give my feedback asap.

Alberto

[OtavioSalvador]

You may want to  try to use 2.6.35 from GIT server at 10.12.01 branch as this is what we've been using in Yocto for i.MX23. I didn't try to change the CPU frequency with it but it has a newer codebase and being the i.MX28 official kernel it might help.

[whitewool]

Hi Otavio,

thanks,

it's ok for this purpose work on ltib 2.6.35 for mx28 just released in the fsl site and set it for mx233, instead of getting the code from the server?

[OtavioSalvador]

No as some issues where fixed on this branch for i.MX23 so you'll need to get it from GIT. Yocto has it ready for use if you are willing to move out from LTIB.