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Date: Mon, 15 Mar 2010 09:11:27 +0100
Message-ID: <2ea1731b1003150111r74032f5fhb52ae0b6e7604800@mail.gmail.com>
Subject: Re: [PATCH v2] char drivers: Ram oops/panic logger
From: Marco Stornelli <marco.stornelli@gmail.com>
To: Jamie Lokier <jamie@shareable.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
       Yuasa Yoichi <yuasa@linux-mips.org>,
       Linux Kernel <linux-kernel@vger.kernel.org>,
       Linux Embedded <linux-embedded@vger.kernel.org>
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2010/3/15 Jamie Lokier <jamie@shareable.org>:
> Marco Stornelli wrote:
>> Il 13/03/2010 00:31, Jamie Lokier ha scritto:
>> I agree, but the bootloader should be aware of it. I mean, usually
>> bootloaders at boot, reset the RAM, so you have to tell to the
>> bootloader that you are using a piece of RAM as persistent RAM, for
>> example U-Boot has got a specific option CONFIG_PRAM. I don't know if
>> all the process can be completely transparent to the admin in all
>> situations.
>
> Sometimes you can't change the bootloader (they don't always come with
> source code).  Or you could, but you don't want to risk it (there
> isn't always a way to recover if you break it).
>
> Obviously then the feature is only useful when the bootloader doesn't
> clear all the RAM :-)
>
> On slow boards in consumer devices, they sometimes avoid clearing the
> RAM because that adds measurable boot time.
>

In the embedded world, usually, you can change/write the fw and you
know well the memory map, so no problem to know the address to use. In
other cases, it can be possible to use a "transparent" approach, but
in my opinion the general approach used by the driver is enough.

Marco