OMAP3 and OPP states

jeffc

Hello,

I have a general question about the OPP states on the OMAP3 devices.

If I change OPP states, let's say from OPP4 to OPP1, what happens with my peripherals that are based on the clock (UART, USB, etc).

Do they automatically shift as well or do I have to manually adjust them to match my new clock frequency?

thanks,

Jeff Cooper

over 16 years ago

0 Bernie Thompson TI over 16 years ago

TI__Mastermind 41665 points

Are you using Linux? In the Linux cpufreq driver everything is managed for you when you change OPP states, there is nothing else special you have do to for individual peripherals.

0 jeffc over 16 years ago in reply to Bernie Thompson TI

Prodigy 180 points

Thanks for the reply.

Yes, I am using Linux and I'm glad to hear that this is taken care of!

What is the proper method for changing the CPU frequency? Is it just a matter of loading the correct cpufreq governor for the behaviour that I want (performance, ondemand, etc)?

thanks,

Jeff

0 Sanjeev Premi over 16 years ago in reply to jeffc

TI__Expert 4590 points

Is it just a matter of loading the correct cpufreq governor for the behaviour that I want (performance, ondemand, etc)?

Exactly.

0 jeffc over 16 years ago in reply to Sanjeev Premi

Prodigy 180 points

Which kernel version has this support in it?

thanks,

Jeff

0 Sanjeev Premi over 16 years ago in reply to jeffc

TI__Expert 4590 points

Are you looking at the TI PSP releases or the latest on the linux-omap community?

Best regards,
Sanjeev

0 jeffc over 16 years ago in reply to Sanjeev Premi

Prodigy 180 points

I have an older kernel, 2.6.28-rc8, that needs to have this ability. I tried to enable it in that kernel but when I booted it, it complained that it couldn't initialize the cpufreq driver.

So, I'm not sure if it's user error or if the cpufreq driver just wasn't working in that version. I'm basically looking for a kernel version that is working so that I can compare/contrast it to my kernel. So I could use either version.

thanks,

Jeff

0 Sanjeev Premi over 16 years ago in reply to jeffc

TI__Expert 4590 points

I am assuming that you are referring to the kernel from linux-omap git.

This feature has been there for sometime, but on a different branch. You can look at the "pm" branch for the cpufreq driver. It is frequently sync'd with the 'master'. However, i must add that i haven't tried to see the level of support for the baseline you are referring to.

If changing the kernel version isn't a big pain for you, i would suggest moving to the pm branch with refresh against 2.6.29. Currently, it is rebased against 2.6.30.

Best regards,
Sanjeev

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OMAP3 and OPP states