Re: port-arm/57139

["Sad Clouds via gnats" <gnats-admin%NetBSD.org@localhost>]

The following reply was made to PR port-arm/57139; it has been noted by GNATS.

From: Sad Clouds <cryintothebluesky%gmail.com@localhost>
To: gnats-bugs%netbsd.org@localhost, port-arm-maintainer%netbsd.org@localhost,
 gnats-admin%netbsd.org@localhost, netbsd-bugs%netbsd.org@localhost
Cc: 
Subject: Re: port-arm/57139
Date: Wed, 24 Dec 2025 08:47:12 +0000

 I think I found a workaround for this issue.
 
 It appears the issue is related to how NetBSD interacts with UEFI. If I
 go into the following UEFI configuration:
 
 "Device Manager" -> "Raspberry Pi Configuration" -> "CPU Configuration"
 
 For "CPU Clock" there are 4 options: Low, Default, Max, and Custom.
 
 Low selects 800MHz, Default and Max select 1500MHz. I had the
 default setting which was Default. However I noticed when I select Low
 then NetBSD command "sysctl -w machdep.cpu.frequency.target" can
 increase CPU frequency above 800MHz but cannot decrease to anything
 below 800MHz.
 
 To work around it in UEFI I select the following options:
 
 "CPU Clock" = Custom and "CPU Clock Rate" = 600 then press F10 to save.
 
 Now I can change CPU frequency between 600MHz and 1500MHz
 
 rp4-4g# sysctl machdep.cpu.frequency
 machdep.cpu.frequency.target = 600
 machdep.cpu.frequency.current = 600
 machdep.cpu.frequency.min = 600
 machdep.cpu.frequency.max = 1500
 machdep.cpu.frequency.available = 600 1500
 
 rp4-4g# sysctl -w machdep.cpu.frequency.target=1500
 machdep.cpu.frequency.target: 600 -> 1500
 
 rp4-4g# sysctl machdep.cpu.frequency
 machdep.cpu.frequency.target = 1500
 machdep.cpu.frequency.current = 1500
 machdep.cpu.frequency.min = 600
 machdep.cpu.frequency.max = 1500
 machdep.cpu.frequency.available = 600 1500
 
 The UEFI "CPU Clock" setting clearly states that an operating system
 can override those settings. I'm not sure why on NetBSD it is only
 possible to override above the minimum of what is set by UEFI and not
 below it.