From: marek.vasut@gmail.com (Marek Vasut)
To: linux-arm-kernel@lists.infradead.org
Subject: Question About Linux Memory Mapping
Date: Sat, 19 Feb 2011 21:22:53 +0100 [thread overview]
Message-ID: <201102192122.53746.marek.vasut@gmail.com> (raw)
In-Reply-To: <AANLkTinUoFzzx4hM8SpUt-mpjn1Z5xmrDqmXwuELuu3e@mail.gmail.com>
On Friday 18 February 2011 21:56:28 Drasko DRASKOVIC wrote:
> Hi all,
> in the article Booting ARM Linux :
> http://www.simtec.co.uk/products/SWLINUX/files/booting_article.html
> I can see that mem map is passed via ATAG_MEM. However, in the same
> article it is mentioned that this information can also be passed via
> kernel command line paramters, mem=<size>[KM][,@<phys_offset>].
>
> However, this does not seem to be true, as "mem" command line
> parameter seems to be formated like this : mem= n[KMG] (i.e. no
> offset), regarding to this reference :
> http://oreilly.com/linux/excerpts/9780596100797/kernel-boot-command-line-pa
> rameter-reference.html. Seems like memmap should be used instead.
>
> I tried passing the parameters like memmap= n[KMG]@start[KMG] but that
> had no effect at all - still the same amount of System Ram was read
> from ATAGS and presented in the system via /proc/iomem.
>
> What I needed it to reserve 1MB region for one FIFO at the end of RAM
> (or somewhere else)
> and protect it from the kernel. I tried passing memmap=
> n[KMG]$start[KMG], but that did not worn neither.
What are you exactly trying to achieve ? btw. if you really need to make a hole
in RAM, you should reserve a bootmem node maybe?
>
> So my questions are following :
> 1) Why commandlines are ignored and ATAGS are given priority ?
> 2) What is the most elegant way to protect one region in RAM :
> a) By giving less memory with ATAGS_MEM and thus making protected
> region invisible to Linux, lying to it that RAM is smaller
> b) By changing somehow linker script
> c) By changing some configuration variables (which ?)
>
> Thanks for the answers and best regards,
> Drasko
>
> _______________________________________________
> linux-arm mailing list
> linux-arm at lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm
next prev parent reply other threads:[~2011-02-19 20:22 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-02-18 20:56 Question About Linux Memory Mapping Drasko DRASKOVIC
2011-02-18 21:55 ` Russell King - ARM Linux
2011-02-18 22:04 ` Nicolas Pitre
2011-02-19 20:22 ` Marek Vasut [this message]
2011-02-21 5:27 ` hong zhang
2011-02-21 12:13 ` Drasko DRASKOVIC
2011-02-21 13:13 ` Russell King - ARM Linux
2011-02-21 14:25 ` Drasko DRASKOVIC
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=201102192122.53746.marek.vasut@gmail.com \
--to=marek.vasut@gmail.com \
--cc=linux-arm-kernel@lists.infradead.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).