Re: enabling powerd on RPi

On Thu, Jan 04, 2024 at 07:53:12AM -0600, Mike Karels wrote:
>On 28 Dec 2023, at 13:11, Mike Karels wrote:
>
>> I am looking at enabling powerd by default on the Raspberry Pi 4 and maybe
>> others.  There is a bug from 2021 on the subject which has gotten some recent
>> discussion, https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=256836.  Also,
>> problems come up from time to time about performance problems because people
>> don't know to enable powerd.  It makes FreeBSD look much slower than Linux.
>>
>> The simplest action is to enable powerd by default on the arm64-aarch64-RPI
>> images.  This would affect RPi 4 and variants, also RPI 3* and later RPi 2.
>> I enabled powerd on an RPi 3B+, and it seems to have no issues; it seems
>> to work.  Does anyone know of a disadvantage of enabling powerd on RPI
>> images for all targets?  The alternative would be to configure at the first
>> boot, although I'm not positive of a definitive way to identify the RPi
>> variants.  Maybe just looking for a dev.cpu.0.freq sysctl node would
>> suffice.
>>
>> If no one objects, I will make changes to enable powerd on RPI snapshots
>> for 15-current, and we can see what happens.
>
>My change to enable powerd for all 64-bit Raspberry Pi systems using the
>arm64-aarch64-RPI image is in https://reviews.freebsd.org/D43296.  There is
>also a review that splits RPi4 from RPi3 (etc); it is
>https://reviews.freebsd.org/D43141.  Comments welcome.

I think powerd by default would be advantageous in most use cases. 
It would be particularly useful in a battery-powered context.

I used to use powerd a lot, but it's not needed for my own uses right now, 
so it's disabled and i overclock by firstly having really efficient cooling 
and then setting config.txt like this

hdmi_safe=0
armstub=armstub8-gic.bin
gpu_mem=16
over_voltage=6
arm_freq=2147
gpu_freq=750
force_turbo=1

# sysctl dev.cpu.0
dev.cpu.0.temperature: 51.0C
dev.cpu.0.freq_levels: 2147/-1
dev.cpu.0.freq: 2147
dev.cpu.0.%parent: cpulist0
dev.cpu.0.%pnpinfo: name=cpu@0 compat=arm,cortex-a72 
dev.cpu.0.%location: 
dev.cpu.0.%driver: cpu
dev.cpu.0.%desc: Open Firmware CPU

My context here is permanently connected to the recommended PSU, headless with serial console
and UPS, and it needs to be responsive, which it is with this overclock.
If I were to use powerd in this context, it would never realise the full overclock
and shows dev.cpu.0.freq_levels: 2100/600.

Connected to it is a usb<>ttl serial cable on the rpi4's pins which is connected to a rpi2b+
running 12.2-RELEASE which is used as a "console server". There is no console scrambling.
Console is invoked on the rpi2b+ with 'cu -l cuaU1 -s 115200'


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