Date: Thu, 18 Mar 2021 12:14:07 -0700 From: Mark Millard <marklmi@yahoo.com> To: bob prohaska <fbsd@www.zefox.net> Cc: freebsd-arm@freebsd.org Subject: Re: RPI4 clock speeds and serial port Message-ID: <5F3752C0-F984-48CE-BA05-526A0C37C1FF@yahoo.com> In-Reply-To: <20210318180736.GA26853@www.zefox.net> References: <20210318170053.GA26688@www.zefox.net> <YFONu3Ry0o6VlV92@ceres.zyxst.net> <20210318180736.GA26853@www.zefox.net>
next in thread | previous in thread | raw e-mail | index | archive | help
On 2021-Mar-18, at 11:07, bob prohaska <fbsd@www.zefox.net> wrote: > On Thu, Mar 18, 2021 at 05:28:27PM +0000, tech-lists wrote: >> hi, >> >> On Thu, Mar 18, 2021 at 10:00:53AM -0700, bob prohaska wrote: >> >>> /boot/msdos/config.txt contains >>> >>> root@nemesis:~ # more /boot/msdos/config.txt >>> [all] >>> arm_64bit=1 >>> dtparam=audio=on,i2c_arm=on,spi=on >>> dtoverlay=mmc >>> dtoverlay=disable-bt Note that use of disable-bt (which is something standard to my context as well). This switches would serial hardware is used, such that the hardware that is not cpu/gpu clock rate dependent is used. I forgot to mention this context in my prior reply. >>> device_tree_address=0x4000 >>> kernel=u-boot.bin >>> >>> [pi4] >>> #hdmi_safe=1 >>> armstub=armstub8-gic.bin >>> >>> Can one change the cpu speed without disturbing the serial console >>> by using something like >>> >>> arm_freq=1750 >>> >>> in config.txt, provided adequate cooling provisions are made? >> >> I have this config.txt on both a rpi4 stable/13 and main/14. I have a >> flirc case on stable/13 and one of those cases that looks like armour >> made from solid metal on main/rpi4. >> In both cases, the approved 5.1V @3.1W power supply is used. >> The highest temp I've seen under load is 72 degC and that's at 25 degC > > 72 C is rather toasty 8-) > >> ambient. On both machines my config.txt looks like this: >> >> arm_control=0x200 >> dtparam=audio=on,i2c_arm=on,spi=on >> dtoverlay=mmc >> dtoverlay=pwm >> dtoverlay=disable-bt >> device_tree_address=0x4000 >> kernel=u-boot.bin >> over_voltage=6 >> arm_freq=2000 >> sdram_freq_min=3200 >> >> In order to clock it, I need to enable powerd on startup in >> /etc/rc.conf: >> >> powerd_enable="YES" >> >> Because I also want that higher clock to run as much as possible, I tell >> powerd to have an absurdly low trigger to get the clocked speed: >> >> powerd_flags="-r 1" >> >> and here's the clocked speed: >> >> % sysctl -a | fgrep cpu.0 >> dev.cpu.0.temperature: 49.6C >> dev.cpu.0.freq_levels: 2000/-1 600/-1 >> dev.cpu.0.freq: 2000 >> 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 >> >>> I'd rather not complicate use of the serial console at this point >> >> not sure why the serial console would be a factor. I have a >> console-wired rpi4 running main/14 and I never considered it. I console >> into this machine like this: >> >> cu -l /dev/cuaU0 -s 115200 >> > > Maybe on FreeBSD it doesn't matter. Pi-related sites report that the > mini-UART baudrate is tied to the clock of the GPU, if that changes > the baudrate changes too. It wasn't clear to me if the speed-changes to > config.txt affected the GPU clock. Apparently not, at least in FreeBSD. You are correct that the mini-UART has the dependencies. But use of: dtoverlay=disable-bt avoids use of the mini-UART. The same is true of instead using: dtoverlay=miniuart-bt but, then, Bluetooth suffers the variability. (I just do not try to use Bluetooth.) === Mark Millard marklmi at yahoo.com ( dsl-only.net went away in early 2018-Mar)
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?5F3752C0-F984-48CE-BA05-526A0C37C1FF>