[One (M7) Original Android Development] tiny4579:
Here's what I saw in logcat:

E/Utils ( 3030): Error writing to /sys/devices/system/cpu/cpu0/cpufreq/scaling_max_freq. Exception:
E/Utils ( 3030): java.io.IOException: write failed: EINVAL (Invalid argument)
E/Utils ( 3030):	at libcore.io.IoBridge.write(IoBridge.java:455)
E/Utils ( 3030):	at java.io.FileOutputStream.write(FileOutputStream.java:187)
E/Utils ( 3030):	at java.io.OutputStreamWriter.flushBytes(OutputStreamWriter.java:167)
E/Utils ( 3030):	at java.io.OutputStreamWriter.close(OutputStreamWriter.java:140)
E/Utils ( 3030):	at com.android.settings.Utils.fileWriteOneLine(Utils.java:561)
E/Utils ( 3030):	at com.android.settings.cyanogenmod.Processor.onPreferenceChange(Processor.java:241)
E/Utils ( 3030):	at android.preference.Preference.callChangeListener(Preference.java:897)
E/Utils ( 3030):	at android.preference.ListPreference.onDialogClosed(ListPreference.java:273)
E/Utils ( 3030):	at android.preference.DialogPreference.onDismiss(DialogPreference.java:390)
E/Utils ( 3030):	at android.app.Dialog$ListenersHandler.handleMessage(Dialog.java:1238)
E/Utils ( 3030):	at android.os.Handler.dispatchMessage(Handler.java:102)
E/Utils ( 3030):	at android.os.Looper.loop(Looper.java:136)
E/Utils ( 3030):	at android.app.ActivityThread.main(ActivityThread.java:5081)
E/Utils ( 3030):	at java.lang.reflect.Method.invokeNative(Native Method)
E/Utils ( 3030):	at java.lang.reflect.Method.invoke(Method.java:515)
E/Utils ( 3030):	at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:781)
E/Utils ( 3030):	at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
E/Utils ( 3030):	at de.robv.android.xposed.XposedBridge.main(XposedBridge.java:126)
E/Utils ( 3030):	at dalvik.system.NativeStart.main(Native Method)
E/Utils ( 3030): Caused by: libcore.io.ErrnoException: write failed: EINVAL (Invalid argument)
E/Utils ( 3030):	at libcore.io.Posix.writeBytes(Native Method)
E/Utils ( 3030):	at libcore.io.Posix.write(Posix.java:202)
E/Utils ( 3030):	at libcore.io.BlockGuardOs.write(BlockGuardOs.java:197)
E/Utils ( 3030):	at libcore.io.IoBridge.write(IoBridge.java:450)
E/Utils ( 3030):	... 18 more

So I removed xposed and I get this error:

E/Utils ( 1319): Error writing to /sys/devices/system/cpu/cpu0/cpufreq/scaling_max_freq. Exception:
E/Utils ( 1319): java.io.IOException: write failed: EINVAL (Invalid argument)
E/Utils ( 1319):	at libcore.io.IoBridge.write(IoBridge.java:455)
E/Utils ( 1319):	at java.io.FileOutputStream.write(FileOutputStream.java:187)
E/Utils ( 1319):	at java.io.OutputStreamWriter.flushBytes(OutputStreamWriter.java:167)
E/Utils ( 1319):	at java.io.OutputStreamWriter.close(OutputStreamWriter.java:140)
E/Utils ( 1319):	at com.android.settings.Utils.fileWriteOneLine(Utils.java:561)
E/Utils ( 1319):	at com.android.settings.cyanogenmod.Processor.onPreferenceChange(Processor.java:241)
E/Utils ( 1319):	at android.preference.Preference.callChangeListener(Preference.java:897)
E/Utils ( 1319):	at android.preference.ListPreference.onDialogClosed(ListPreference.java:273)
E/Utils ( 1319):	at android.preference.DialogPreference.onDismiss(DialogPreference.java:390)
E/Utils ( 1319):	at android.app.Dialog$ListenersHandler.handleMessage(Dialog.java:1238)
E/Utils ( 1319):	at android.os.Handler.dispatchMessage(Handler.java:102)
E/Utils ( 1319):	at android.os.Looper.loop(Looper.java:136)
E/Utils ( 1319):	at android.app.ActivityThread.main(ActivityThread.java:5081)
E/Utils ( 1319):	at java.lang.reflect.Method.invokeNative(Native Method)
E/Utils ( 1319):	at java.lang.reflect.Method.invoke(Method.java:515)
E/Utils ( 1319):	at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:781)
E/Utils ( 1319):	at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
E/Utils ( 1319):	at dalvik.system.NativeStart.main(Native Method)
E/Utils ( 1319): Caused by: libcore.io.ErrnoException: write failed: EINVAL (Invalid argument)
E/Utils ( 1319):	at libcore.io.Posix.writeBytes(Native Method)
E/Utils ( 1319):	at libcore.io.Posix.write(Posix.java:202)
E/Utils ( 1319):	at libcore.io.BlockGuardOs.write(BlockGuardOs.java:197)
E/Utils ( 1319):	at libcore.io.IoBridge.write(IoBridge.java:450)
E/Utils ( 1319):	... 17 more

I verified the permissions are fine. You might be right about the kernel [MENTION=4513061]cschmitt[/MENTION].

I seem to recall an issue mentioned in gerrit with the way uevents are handled or not handled at the kernel level since kitkat. I tested on my toro and I can set max freqs properly so it's not at the CM level.

EDIT: I don't think it's uevents since changing the governor is fine.

EDIT 2: One thing I noticed, I can set scaling_max_freq to 1350000 for instance and it works which I can confirm via cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_min_freq. Maybe it's powerHAL related since once I touch the screen a bit and swipe my finger around, it gets reset to 1728000/1728000.