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From: Jia-Shiun Li <jiashiun@gmail.com>
Date: Tue, 1 Oct 2013 05:04:29 +0800
Message-ID: <CAHNYxxM5Lhytd8J-A7TvaXm05sMjFM1ghROhLthyV9uCVGishQ@mail.gmail.com>
Subject: Re: BBB CPU clock (was: Re: FreeBSD on Cubieboard 2, UDOO and Galaxy
 Note 10.1 (Exynos).
To: Tim Kientzle <kientzle@freebsd.org>
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Cc: "freebsd-arm@freebsd.org" <freebsd-arm@freebsd.org>, ticso@cicely.de
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On Mon, Sep 30, 2013 at 11:26 AM, Tim Kientzle <kientzle@freebsd.org> wrote:
>
> My understanding:
>
>   * We should query the PMIC to determine whether we're running from 5V supply or USB.
>
>    * Based on that, we should adjust the CPU clocks.  We should be able to run 1GHz from 5v supply.
>
> Connecting cpufreq would be a nice addition.

Hi Tim,

Yes you are right. I digged a bit the PMIC docs.
I didn't realize that DCDC2/3 output to MPC/core are adjustable.

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.

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.

Thanks,
Jia-Shiun.