On Tue, 21 Feb 2006, anand bhavnani wrote:
> The manual mentions that the processor clock is dynamically adjustable
> from 0 to 200 MHZ but doesn't mention how... can anyone please help me
> out...
There has been some discussion of this on this list, so a search of the
archives at yahoo might help. But here is an email I sent to the cirrus
linux list which covers this and more. You also will need the user manual
from the cirrus web site (EP9301 manual is ok in this area - that's what I
used). There are several clock settings that are interconnected - cpu,
memory, buses - and the PLL settings are reasonably complex. Good luck
Jim
Date: Thu, 1 Sep 2005 17:29:32 +0100 (BST)
From: Jim Jackson <>
To: "Linux-Cirrus Liste (E-Mail)" <>
Subject: [linux-cirrus] Re: Clock Setting on EDB9307
Reply-To:
On Thu, 1 Sep 2005, Jahn, Olav wrote:
> Hello all,
>
> first of all, let me introduce myself with a few words:
>
> we are currently trying to build our own board using the Cirrus EP9307
>..... snip......
If the 9307's PLL stuff is the same as the 9301/2 then I have some user
space code for querying the PLL values and setting them at
http://www.comp.leeds.ac.uk/jj/linux/cctl-0.1beta.tgz
and there is a set of patches for the Kernel source for the TS7200
from Technologics which adds some kernel code for altering the internal
clocks (cpufreq). This patch is in the files section of
http://groups.yahoo.com/group/ts-7000/
the ts-7000 yahoo group in the files section. The TS72?0 boards are based
on EP9301/2.
> Actually the unmodified Linux is still working on the board. We just
> gave it a try and started it, cause we thought 100BogoMIPS -> 100 MHz
> -> faster crystal and same PLL will give ~170 MHz (with UARTs and USB
> not working anymore). Well - the console on my PC did not work
> anymore, yet the USB-keyboard connected to the board did and CPU-info
> gave us ~58 BogoMIPS which is factor 1.7 smaller not higher.
> Meanwhile I found out, the Linus' BogoMIPS have nothing to do with
> Cirrus' announced 200 MIPS for the EP9307,
For info on what the "Bogomips" is and is NOT try this....
http://www.tldp.org/HOWTO/BogoMips/
> but now I'm really
> confused:
> How did the kernel work anyway (with faster crystal)? And even more
> set the USB clock rate so that it was still working? If there is some
> auto-detection, why didn't it set it so, that again 100 BogoMIPS come
> out?
> Is there any way to find out the real actual clock settings in Linux
> and RedBoot - cause anything else is only guessing?
I think that the PLL settings are set before Linux is loaded, by Redboot
or even earlier. Linux just uses the PLL settings it has inherited. I
think.
> That shall be enough for the moment being. I'm looking forward to any
> help and thank you in advance for it.
I hope that helps somewhat
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