RBPI3B+ clock speed

[Ralf Wenk]

On 2018-10-26 at 7:40 +0300 Stefan Parvu wrote:
> > - How can I see the current clock speed my RBPI is using at any moment ?
> 
> by checking system’s variables:
> 
> dev.cpu.0.freq_levels: 1400/-1 600/-1
> dev.cpu.0.freq: 1400
> 
> this means now my system is using 1400 frequency vs 600. 
> 
> > 
> > - How would you change the frequency of the clock speed which by
> > default seems 
> > set to 600MHz ? 
> 
> by simple setting powerd during rc.conf or manually start it. 
> 
> Are these correct ?

Last time I tried powerd(8) on a RPi3B+ it was complaining about missing
a CPU clock driver.
Meanwhile I did not read anything in the repository log about work on
that issue. So probably powerd(8) will not work.

A RPi3B shows more information about CPU frequency(s) than you provided:

$ sysctl -a | fgrep cpu | fgrep freq
debug.cpufreq.verbose: 0
debug.cpufreq.lowest: 0
hw.cpufreq.temperature: 49388
hw.cpufreq.voltage_sdram_p: 1200000
hw.cpufreq.voltage_sdram_i: 1200000
hw.cpufreq.voltage_sdram_c: 1200000
hw.cpufreq.voltage_core: 1256250
hw.cpufreq.turbo: 1
hw.cpufreq.sdram_freq: 450000000
hw.cpufreq.core_freq: 400000000
hw.cpufreq.arm_freq: 1200000000
dev.cpufreq.0.%parent: cpu0
dev.cpufreq.0.%pnpinfo: 
dev.cpufreq.0.%location: 
dev.cpufreq.0.%driver: cpufreq
dev.cpufreq.0.%desc: 
dev.cpufreq.%parent: 
dev.bcm2835_cpufreq.0.freq_settings: 1200/-1 600/-1
dev.bcm2835_cpufreq.0.%parent: cpu0
dev.bcm2835_cpufreq.0.%pnpinfo: 
dev.bcm2835_cpufreq.0.%location: 
dev.bcm2835_cpufreq.0.%driver: bcm2835_cpufreq
dev.bcm2835_cpufreq.0.%desc: CPU Frequency Control
dev.bcm2835_cpufreq.%parent: 
dev.cpu.0.freq_levels: 1200/-1 600/-1
dev.cpu.0.freq: 1200
$ 

Occasionally powerd(8) gets into trouble on this RPi3B.

mbox0: mbox response error
bcm2835_cpufreq0: can't set clock rate (id=3)
mbox0: mbox response error
bcm2835_cpufreq0: can't get clock rate (id=3)
bcm2835_cpufreq0: wrong freq
bcm2835_cpufreq0: set freq failed, err 5
mbox0: mbox response error
bcm2835_cpufreq0: can't set clock rate (id=8)

Which seems to depend on the kernel release. Some are working for weeks
without that issue, others only 24 hours. The samples came from revision
339388.

Regards Ralf