BBB CPU clock (was: Re: FreeBSD on Cubieboard 2, UDOO and Galaxy Note 10.1 (Exynos).

[Bernd Walter]

Am 29.09.2013 um 22:01 schrieb Jia-Shiun Li <jiashiun at gmail.com>:

> On Mon, Sep 30, 2013 at 12:41 AM, Jia-Shiun Li <jiashiun at gmail.com> wrote:
>> But I manually modified registers using the sequence in mpu_pll_config() of
>> u-boot and got the MPU clocked at the value I gave. There seems to be some
>> unknown sequences in u-boot either skipping or overwriting MPU PLL settings.
> 
> Never mind. Have to copy MLO in addition to u-boot.img as well.
> Looks like PLL init part is there.
> 
> However, I cannot set MPU clock to 800 MHz and beyond. Now booting ok at
> 750MHz. Maybe a heat sink or active cooling is required. Will try when
> I get one.

That matches with what the NetBSD list describes.
You also need to configure the PMIC to deliver a higher core
voltage for higher frequencies.
If you don't your systems becomes unstable.

> cpufreq for ARM boards may be possible provided frequency can be changed
> dynamically. But if the board cannot provide a way to determine
> stability reliability it may be impractical to make it automatic.
>