And I got this bit from
http://ftp.kelp.or.kr/pub/arm-linux/people...2004/README.txtfreq: the desired frequnecy in khz;
n_value: the N value in CCCR;
fast_bus_mode: [0|1], to specify switch to fast bus mode or not.
For example,
# dvfm 104000 2 0
will switch the system to 104Mhz, with N=2 means RUN mode,no fast bus mode.
# dvfm 65000 5 1
will switch the system to 65Mhz, with N=5 means TURBO mode,fast bus mode.
Note: Please refer to Intel PXA27x Process Developer's Kit manual to know the combination of freq N and fast_bus_mode, incorrect combination will hang the system, or even damage the hardware!
So, how to use dvfm to set the clock precisely?
[EDIT]I tool a look at the cpuoverclock.py script and found the relevant chunk:
FREQ_TAB = ["104", "208", "312", "416", "520", "624"]
CCCR_L_TAB = [ "8", "16", "16", "16", "16", "16"]
CCCR_2N_TAB = [ "2", "2", "3", "4", "5", "6"]
...
...
...
CMD = "dvfm " + self.CPU_CCCR_L + " " + self.CPU_CCCR_2N + " 1 2 1"
So I tried
dvfm 16 5 1 2 1(the spaces are important!)
(I notice that in the titchy wiki comments someone called ip-206-32 has posted similar things, but perhaps due to the display problem his commands are not shown properly with irregular spacing.)
L:16 ZN:5 b:1 t:2
vm_setvoltage: write 0C
Set frequency to 520000 with L:16 ZN:5 B:1 Turbo Mode, A:1
Calibrating delay loop... 517.73 BogoMIPS (lpj=2588672)
(Don't ask me what's going on here as I am no computer guru)
Then I got
520 (517.73) mhz, as confirmed by
cat /proc/cpuinfo.
dvfm 16 4 1 2 1 (again, mind the spacing!) brings me back to
416 (415.33) mhz. And so on.
But still there is screen flickering after overclocking...