[oe] hawkboard at 456 Mhz?

[Frans Meulenbroeks]

2010/3/22 Koen Kooi <k.kooi at student.utwente.nl>:
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> On 21-03-10 20:38, Frans Meulenbroeks wrote:
>> 2010/3/21 Koen Kooi <k.kooi at student.utwente.nl>:
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>>> On 21-03-10 13:57, Frans Meulenbroeks wrote:
>>>> Hi,
>>>>
>>>> In the openembedded repository I saw the following patch:
>>>> http://cgit.openembedded.org/cgit.cgi/openembedded/tree/recipes/linux/linux-davinci/da850_omapl138_opp456mhz.patch
>>>> This seems to suggest that it is possible to run the hawkboard at 456
>>>> Mhz (and yeah: I know it is out of spec and out of warranty, but for
>>>> an experiment it would be quite helpful for me).
>>>> I've build the kernel with openembedded, the patch is applied,
>>>> CONF_CPU_FREQ is defined, but the control hook in /sys is not there.
>>>> I've also tried tweaking the file with the settings (ds850.c) but to no avail.
>>>>
>>>> Anyone a suggestion on how to get this done?
>>>
>>> You need a newer kernel that doesn't rely on the TPS part for cpufreq
>>> (hawkboard lacks a PMIC, the evm uses the TPS). You can build from the
>>> ti/staging[1] branch to get such a kernel.
>>>
>>> Or wait a week for that branch to get merge, internal testing is finally
>>> wrapping up.
>>>
>>> [1] http://gitorious.org/angstrom/openembedded/commits/ti/staging
>>
>>
>> Koen,
>>
>> Thanks alot!
>> As patience is something that I don't have an overdose of, I decided
>> not to waste any on this issue.
>> So I checked out the git and rebuild the kernel. Works like a charm.
>>
>> For those who want to reproduce this:
>> Be sure to adapt defconfig (CONFIG_DA8XX_MAX_SPEED_456=y)
>>
>> I changed the speed setting with cpuspeed, this one is not on the
>> angstrom feed, so you need to build it yourself too.
>
> I use cpufrequtils, is cpuspeed a better option?

I was unaware of cpufrequtils and bumped into cpuspeed, so I used that.
I just quickly browsed the manpage of cpufreq-set and it would have
served me better (as cupfreq-set has a -f option to force the speed
and cpuspeed is controlled to signals.
Here is the manpage for cpuspeed: http://linux.die.net/man/8/cpuspeed

Btw I would have expected that I could also directly poke in /sys to
change the speed but the one attempt I did gave an error. Might be
that I just used the wrong var
(actually i probably had to use scaling_set_speed and I probably used
something like actual_speed or current_speed).

Frans.

PS: i've briefly peeked at the processor doc: would it be possible to
push things even further (e.g. to 600 Mhz). Of course I know this is
out of warranty, but that is 456 too :-) I'm still missing some info
on how to play with what to do an educated attempt (it is manly the
voltage related settings I feel unsure about).