linux-kernel - Re: [BUG] panda board locks up on boot

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Date:	Sun, 27 Jan 2013 08:33:54 -0600
From:	Nishanth Menon <menon.nishanth@...il.com>
To:	Paolo Pisati <p.pisati@...il.com>
CC:	Mats Liljegren <mats.liljegren@...a.com>,
	Tony Lindgren <tony@...mide.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Igor Grinberg <grinberg@...pulab.co.il>,
	Russell King <rmk+kernel@....linux.org.uk>,
	Venkatraman S <svenkatr@...com>,
	linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
	linux-omap <linux-omap@...r.kernel.org>
Subject: Re: [BUG] panda board locks up on boot

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@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
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