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Observer avnetwatson
Observer
6,809 Views
Registered: ‎01-02-2013

cpu clock freq change

Hi,

 

I found the following message during linux boot up and running linaro ubuntu.

 

cpufreq_cpu0: failed to set clock rate: -16

cpufreq: __cpufreq_driver_target: Failed to change cpu frequency: -16

 

The system can still work but the above messages appear periodically.

 

What's wrong?

 

I'm using xilinx kernel @tag version xilinx-2014.2

 

watson

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5 Replies
Scholar milosoftware
Scholar
6,792 Views
Registered: ‎10-26-2012

Re: cpu clock freq change

Current kernel reports to be able to switch to 222 MHz, but when ask to do so, it errors. The 333 and 666 settings work fine.

 

This is related to the change to allow only multiple-of-2 dividers which apparently doesn't filter out the unsupported ones to the governor. The governor then tries to switch to frequencies that do not work.

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Observer avnetwatson
Observer
6,776 Views
Registered: ‎01-02-2013

Re: cpu clock freq change

Thanks 

 

Is this a kernel issue ?

 

 

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Visitor asigint
Visitor
6,710 Views
Registered: ‎10-02-2013

Re: cpu clock freq change

To get rid of the message, I made the following change to my device tree:

 

In the section: ps7_cortexa9_0: cpu@0 {}

 

change from:

 

operating-points = <666667 1000000 333334 1000000 222223 1000000>;

 

to:

 

operating-points = <666667 1000000 333334 1000000>;

 

This doesn't really fix anything, other than to stop trying to use 222MHz which doesn't seem to work. If anyone knows how to fix it please share.

 

Also, it seems you should be able to set the frequency with a command like:

echo 666667 > /sys/devices/system/cpu/cpu0/cpufreq/scaling_setspeed

 

but that doesn't work for me. I get

echo: write error: Invalid argument

 

Not sure if this is related.

 

Jerry

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Xilinx Employee
Xilinx Employee
6,702 Views
Registered: ‎03-13-2012

Re: cpu clock freq change


@asigint wrote:

Also, it seems you should be able to set the frequency with a command like:

echo 666667 > /sys/devices/system/cpu/cpu0/cpufreq/scaling_setspeed

 

but that doesn't work for me. I get

echo: write error: Invalid argument



What governor are you using? I suspect anything else, but not 'userspace'. Hence, no userspace control over the frequency.

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Visitor vibishna
Visitor
3,668 Views
Registered: ‎05-03-2016

Re: cpu clock freq change

I know this is a very old post. But I thought it is worth discussing.

 

This problem started popping up, once I started playing with the governor in menu config. I can get rid of this problem using the following command instantaneously:

 

"sudo cpufreq-set -g userspace"

 

I made a script to run this command on boot up. But that did not work. I have to issue the above command only after this error gets displayed. 

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