HSB clock rate reduction on NGW100

Go To Last Post
3 posts / 0 new
Author
Message
#1
  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

Hi,

I'm currently working on a project where I don't need that much computational power and where I have to reduce power consumption as much as possible.

I've played around with clock rate changes for CPU, HSB, PBA and PBB during the last days.

I plan to use the following configuration:
CPU: 60MHz, HSB: 30MHz, PBA: 15MHz, PBB: 30MHz

The system runs stable with this setup when I boot via NFS.

But when booting from internal FLASH, I get JFFS2 file system errors during the boot process.

These errors occur as soon as the HSB frequency goes below the standard 70 MHz.
I suspect a FLASH timing setup problem.

Does anybody have an idea? Are there clock rate related dependencies in the FLASH or JFFS2 configuration that I have to adjust?

I use Buildroot 2.3.0 and kernel 2.6.27.6.

Gerhard

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

hi folks,

sorry for a stupid question, but i'm currently playing with the cpu, pba and pbb clock rates.

i'm a bit confused because since i changed the clock rates in the u-boot config and uploaded the bootloader into flash memory, no entry like 'CPU: 140 Mhz HSB: 70 MHz PBA: 35 MHz PBB: 70 MHz' (<= NGW100 default settings) appearing in the u-boot startup message anymore.

what's wrong!?
is there any other possibility to confirm the current clock rates of CPU, PBA and PBB? (maybe while linux kernel is running?)

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

I think the magic incantation is something like

#: mount -t debugfs none /sys/kernel/debug
#: cat /sys/kernel/debug/at32_clks

Anyway there's a debug attribute in debugfs which, once you mount debugfs, will contain all the data you're after.

Note that if you have CPU frequency scaling enabled then the CPU frequency in particular might not be what you expect..

-S.