From mboxrd@z Thu Jan  1 00:00:00 1970
From: menon.nishanth@gmail.com (Nishanth Menon)
Date: Sun, 27 Jan 2013 08:33:54 -0600
Subject: [BUG] panda board locks up on boot
In-Reply-To: <20130127141254.GC5714@stinkpad>
References: <1359082886.21576.199.camel@gandalf.local.home>
 <51022FD2.8090101@compulab.co.il>
 <0247700D01F14443B9209F90AD938CC52409708C@sestoex09.enea.se>
 <20130127141254.GC5714@stinkpad>
Message-ID: <51053AD2.8080805@gmail.com>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

On 01/27/2013 08:12 AM, Paolo Pisati wrote:
> On Fri, Jan 25, 2013 at 08:43:15AM +0000, Mats Liljegren wrote:
>> Hi Steven,
>>
>> Do you have CONFIG_CPU_FREQ enabled? As I posted earlier in linux-kernel forum ("Failed booting PandaBoard ES with Linux 3.8 RC4" two days ago) my PandaBoard ES hangs while booting with this option enabled. It works fine without it. I have not bisected it down to a single commit though.
>
> glad i'm not the only one who hit this problem:
>
> "3.8rc4+ and cpu_freq omap: hangs, oopses, etcetc"
>
> http://www.mail-archive.com/linux-omap at vger.kernel.org/msg83693.html
>

Support for TPS is not yet in mainline kernel. you may want to do:

you could try running 'mw.w 0x4A31E05A 0x1' before bootm in u-boot -> 
This will hack the pad of panda ES pin mean for controlling TPS voltage 
register (again a kernel bug where the GPIO block setup by bootloader 
got reset).

CPUfreq needs both voltage and frequency scaling to work and without 
support of the TPS voltage scaling on vdd_MPU, you are stuck at boot 
voltage, and just scaling frequency. with the not-enough boot voltage, 
moving to higher frequencies can/will result in unpredictable behavior.

---
Regards,
NM