Date: Tue, 1 Oct 2013 09:12:10 -0400 From: Paul Mather <paul@gromit.dlib.vt.edu> To: Jia-Shiun Li <jiashiun@gmail.com> Cc: "freebsd-arm@freebsd.org" <freebsd-arm@freebsd.org>, ticso@cicely.de Subject: Re: BBB CPU clock (was: Re: FreeBSD on Cubieboard 2, UDOO and Galaxy Note 10.1 (Exynos). Message-ID: <603C57BE-8DCE-4178-B912-DBBB5CAC93B3@gromit.dlib.vt.edu> In-Reply-To: <CAHNYxxM5Lhytd8J-A7TvaXm05sMjFM1ghROhLthyV9uCVGishQ@mail.gmail.com> References: <CAHNYxxPtD5vgrohumwccoC_5bZv7fuV3RYK2vgLUpyEZCmOgqg@mail.gmail.com> <B8966F22-1169-4FE5-B105-4D104909723E@freebsd.org> <CAHNYxxM5Lhytd8J-A7TvaXm05sMjFM1ghROhLthyV9uCVGishQ@mail.gmail.com>
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On Sep 30, 2013, at 5:04 PM, Jia-Shiun Li <jiashiun@gmail.com> wrote: > On Mon, Sep 30, 2013 at 11:26 AM, Tim Kientzle <kientzle@freebsd.org> = wrote: >>=20 >> My understanding: >>=20 >> * We should query the PMIC to determine whether we're running from = 5V supply or USB. >>=20 >> * Based on that, we should adjust the CPU clocks. We should be = able to run 1GHz from 5v supply. >>=20 >> Connecting cpufreq would be a nice addition. >=20 > Hi Tim, >=20 > Yes you are right. I digged a bit the PMIC docs. > I didn't realize that DCDC2/3 output to MPC/core are adjustable. >=20 > The PMIC capped USB input at 500mA by default, so if not changed = otherwise, > or to be safe with what most USB power supplies are, it is correct to = only go up > to 1GHz on DC input. >=20 > I played for a while manually setting PMIC from u-boot prompt, setting = MPU volt > to 1.325v, raise USB current limit, etc. but still cannot get it run > above 800MHz. > It always stopped booting at initing uhub. Looks like I need a bigger > DC adapter. What 5V adapter are you using? The one recommended by Adafruit for the = BeagleBone Black is a 5V 2A adapter. The BBB system reference manual = states, "A 5VDC supply can be used to provide power to the board. The = power supply current depends on how many and what type of add-on boards = are connected to the board. For typical use, a 5VDC supply rated at 1A = should be sufficient. If heavier use of the expansion headers or USB = host port is expected, then a higher current supply will be required." = The BBB Wiki = (http://circuitco.com/support/index.php?title=3DBeagleBoneBlack) lists = the power consumption of the BBB itself as 210--460 mA@5V depending on = "activity and processor speed." I believe if you use capes with the BBB = then you need to use the external PSU. I've personally found the BBB to be a bit flaky when run via the USB OTG = connector. I prefer to run it via a 5V external PSU for stable = operation. Cheers, Paul.
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