The Rev C4 board has a 720MHZ processor. It does require SW running on the processor to set it to 720MHz.
Gerald
It is not set “by default”. When u-boot starts it detects the CPU version by reading SKUID register. If u-boot finds 720MHz version it sets special environment variable “mpurate” to “720”. This variable also has possible values: 500, 600, 720. You can override u-boot setup for this variable.
When the kernel starts it reads the variable mpurate and sets the CPU fequency respectively.
2010/8/16 Gerald Coley <gerald@beagleboard.org>
hi,
Maxim Podbereznyy wrote On 16-08-2010 19:10:
It is not set “by default”. When u-boot starts it detects the CPU version by reading SKUID register. If u-boot finds 720MHz version it sets special environment variable “mpurate” to “720”. This variable also has possible values: 500, 600, 720. You can override u-boot setup for this variable.
i have a rev c2 board(beagleboard). i built a narcissus image and when i check cpu frequency, cpufreq-info says cpu is running at 720 MHz. in this case, does rev c2 boards support 720 MHz?
Rev C2 is a 600MHz processor. I might run at 720MHz but it is not guranteed to do so.
Gerald
Cihan,
you can find out what is going on by checking dmesg output in working Linux. You will find parameters sent to the kernel from u-boot and among them may be mpurate variable. Compare the value there with the one from cpufreq-info. If they are different then you can report it here as a bug.
I remember how many attempts were to make the code detecting the board revision stable and it wouldn’t be a surprise if there is a bug there.
2010/8/16 Gerald Coley <gerald@beagleboard.org>
hi,
i couldnt find anything on dmesg output because first 15 second is missing. on printenv output, value of mpurate is 600 but according to cpufreq-info, cpu runs 720 MHz. i attached dmesg, printenv and cpufreq-info logs.
Maxim Podbereznyy wrote On 16-08-2010 21:38:
cpufreq-info.log (2.94 KB)
dmesg.log (15.5 KB)
printenv.log (3.61 KB)
@maxim Podbereznyy
Hi
I set the environment variable mpurate to be 500 in the u-boot prompt
after that i gave a saveenv and then reset the board
but still it takes the mpurate as 720.
Any idea why ?
PS: when i set the variable and give a boot command in the prompt
immediately in the prompt it take the correct value( the mpurate as
500)
Well, I’m pretty sure that your CPU runs at 720MHz. But you’d better find those 15sec which are missing.
2010/8/17 Cihan Kaya <kayacin@gmail.com>
Dear Cihan,
The TI kernel team modified the kernel to have all 3530 revisions use 720MHz when using cpufreq.
Paul Menzel wrote On 17-08-2010 10:47:
Dear Cihan,
i couldnt find anything on dmesg output because first 15 second is
missing.Did you try to redirect the output to a file: `dmesg> dmesg.output`?
yes i did. dmesg.log is output of "dmesg > dmesg.log" command.
actually i changed boot parameters and now i can see boot output during boot. i attached complete output. but no information about mpurate. i added "mpurate=600" to bootargs but nothing changed.
boot.log (40.9 KB)
A full dmesg should answer this.. 
bootarg is setup to pass the mpurate from u-boot: mpurate=${mpurate}
[ 0.000000] Kernel command line: console=ttyS2,115200n8 <cut> mpurate=720
boot as:
[ 0.000000] Clocking rate (Crystal/Core/MPU): 26.0/332/500 MHz
and just a bit later, the change to 720..
[ 0.000000] Switched to new clocking rate (Crystal/Core/MPU):
26.0/720/332 MHz
so my board is running 720...
Regards,
Guys!
If Koen writes that TI changed the kernel this means that there is no more mpurate needed. I will try to omit these changes because I’m not sure that 3530 Automotive version is able to work at 720MHz under +85deg of ambient temperature…
2010/8/17 Robert Nelson <robertcnelson@gmail.com>
Guys!
If Koen writes that TI changed the kernel this means that there is no more *mpurate* needed. I will try to omit these changes because I'm not sure that 3530 Automotive version is able to work at 720MHz under +85deg of ambient temperature..
If you don't use cpufreq or any automatic cpufreq governor, you can still pass mpurate to set the frequency and voltage that way.
regards,
Koen
Koen,
how can I disable cpufreq? I suppose either I set mpurate or not it does not matter, right?
2010/8/17 Koen Kooi <koen@beagleboard.org>