Re: [Gumstix-users] request for help on direct mapping access - Overo Water

[Keane, B. (STRX) <ben...@ka...>]

I believe once you get the source and get your own OE system building - you may be able to edit the board file under the Linux Kernel to remove turning on the SPI Clocks so then your application can have access. 

I use Android on the Gumstix platform and not OE, so a rough guess once you have all that setup the file would be in ./tmp/work/overo-angstrom-linux-gnueabi/linux-omap3-2.6.39-r102/git/arch/arm/mach-omap2/board-overo.c   - of course this directory is just a guess.

Ben

-----Original Message-----
From: Dave Hylands [mailto:dhy...@gm...] 
Sent: Tuesday, 14 August 2012 2:41 AM
To: General mailing list for gumstix users.
Subject: Re: [Gumstix-users] request for help on direct mapping access - Overo Water

Hi Nicola,

On Mon, Aug 13, 2012 at 9:17 AM, Nicola <pa...@li...> wrote:
> Hi Dave. Sincerely, since two months ago I've been working on an ATMEL 
> ARM9 processor with his embedded linux on and I was able to control 
> all registers of the processor....unfortunately it was not enough powerful for my aims.
> I switched to Gumstix thinking to find all support I would have needed 
> but Gumstix doesn't offer any software consulence.
> The file you suggested my to find doesn't exist on the Angstrom linux 
> stable version that Gumstix supplies..... I don't know how to procede. 
> Before giving up with this (not well supported) electronics I'd like 
> to find a simplified linux version that simply allows me to "see" the 
> processor register. I'm working on an expensive project and I have no 
> time to "play" .

I've been assuming that you have a fully-built open-embedded tree. If you don't, I suggest you build one. If you just download the sources, then no you won't have a .config file. You need to actually build the tree.

Once you do, you can find your kernel .config file by using the find command.

Something like

cd overo-oe
find . -name .config

This will also find some other .config files. You can find the directory where the kernel is built by doing something like

find . -name do_mount.o

The do_mount.c file is normally located in the init directory, so strip that off and you

You are accessing registers, youprobably just aren't following all of the rules properly (which has nothing to do with the linux kernel).
You probably need to familiarize yourself with the appropriate OMAP Technical Reference Manual.

Turning off the clocks is done to save power and is a common technique used in most newer processors (the ARM926 is relatively ancient). So you'll run across similar problems regardless of which platform you choose, if it uses a relatively new processor.

So, to summarize, "seeing the register" has almost nothing to do with linux, or which version of linux you're using. It has everything to do with the underlying SoC and what it requires to make the registers visible. Normally this work is done by the appropriate device driver, sometimes by the platform code.

--
Dave Hylands
Shuswap, BC, Canada
http://www.davehylands.com

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