Date: Thu, 18 Mar 2021 14:41:05 -0700 From: Mark Millard <marklmi@yahoo.com> To: Diane Bruce <db@db.net> Cc: bob prohaska <fbsd@www.zefox.net>, freebsd-arm@freebsd.org Subject: Re: RPI4 clock speeds and serial port Message-ID: <7736E7C9-173A-4823-8B0E-869157AD1CC1@yahoo.com> In-Reply-To: <E384D160-E31A-42A0-AA54-F5AD991FFA4D@yahoo.com> References: <20210318170053.GA26688@www.zefox.net> <YFONu3Ry0o6VlV92@ceres.zyxst.net> <20210318180736.GA26853@www.zefox.net> <20210318203835.GA83932@night.db.net> <E384D160-E31A-42A0-AA54-F5AD991FFA4D@yahoo.com>
next in thread | previous in thread | raw e-mail | index | archive | help
On 2021-Mar-18, at 14:21, Mark Millard <marklmi at yahoo.com> wrote: > On 2021-Mar-18, at 13:38, Diane Bruce <d at db.net> wrote: >=20 >> On Thu, Mar 18, 2021 at 11:07:36AM -0700, bob prohaska wrote: >>> On Thu, Mar 18, 2021 at 05:28:27PM +0000, tech-lists wrote: >>>> hi, >>>>=20 >>>> On Thu, Mar 18, 2021 at 10:00:53AM -0700, bob prohaska wrote: >>>>=20 >> ... >>> bob prohaska >>>=20 >>=20 >> I've been meaning to get someone to look this over but basically this >> rejigs the mini-uart baud rate depending on the CPU clock.. >>=20 >>=20 >> https://reviews.freebsd.org/D24339 >=20 > I'm confused. The RPi* firmware dynamically > assigns which UART used for the serial console > based on other settings (including a default > context). >=20 > For the default, with Bluetooth in use the > miniuart is used for the serial console and > the PL011 for Bluetooth. (Only the miniuart > has the speed variability issue.) >=20 > But with either ( in config.txt ): >=20 > dtoverlay=3Ddisable-bt > or: > dtoverlay=3Dminiuart-bt >=20 > the PL011 is used for the serial console. > That last uses the miniuart for Bluetooth > as well, letting it suffer the variability. >=20 > Is the proposed change compatible with > this? Is it compatible with Bluetooth > being what is using the miniuart? >=20 > (Note: I happen to use dtoverlay=3Ddisable-bt .) >=20 Now I'm even more confused: = https://www.raspberrypi.org/documentation/configuration/config-txt/overclo= cking.md reports for the RPi4: QUOTE Changing core_freq in config.txt is not supported on the Pi 4 any change from the default will almost certainly cause a failure to boot. END QUOTE Or, more completely, it reports ties with hdmi_enable_4kp60 and enable_tvout for core_freq: QUOTE The core_freq of the Raspberry Pi 4 can change from the default if either hdmi_enable_4kp60 or enable_tvout are used, due to relationship between internal clocks and the particular requirements of the requested display modes. Display option Frequency Default 500 enable_tvout 360 hdmi_enable_4kp60 550 Changing core_freq in config.txt is not supported on the Pi 4, any change from the default will almost certainly cause a failure to boot. It is recommended when overclocking to use the individual frequency settings (isp_freq, v3d_freq etc) rather than gpu_freq, as since it attempts to set core_freq (which cannot be changed on] the Pi 4), it is not likely to have the desired effect. END QUOTE = https://www.raspberrypi.org/documentation/configuration/config-txt/overclo= cking.md also documents the Pi3/Pi3A+/Pi3B+ as using a 400 MHz core_freq (Pi0/W as well). Only the Pi1/Pi2 list 250 MHz. My guess is that "Pi2" means RPi2 V1.1 and below, not the RPi2 V1.2 as well. It is true that the "core_freq_min" figures are almost all 250 MHz: RPi4 lists 250 MHz / 275 MHz with no clear indication of the context difference for 275 MHz that I can find. Have you covered what all the: = https://www.raspberrypi.org/documentation/configuration/config-txt/overclo= cking.md page reports for things that you are planning to touch? =3D=3D=3D 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?7736E7C9-173A-4823-8B0E-869157AD1CC1>