From: Sascha Hauer <s.hauer@pengutronix.de>
To: Giorgio Dal Molin <giorgio.nicole@arcor.de>
Cc: barebox@lists.infradead.org
Subject: Re: barebox for a ti am335x based board
Date: Fri, 16 Feb 2018 08:51:58 +0100 [thread overview]
Message-ID: <20180216075158.srw63pfrlby67oub@pengutronix.de> (raw)
In-Reply-To: <ba32e817-48b6-9266-ffd7-d2397d103f7a@arcor.de>
Hi Giorgio,
On Tue, Feb 13, 2018 at 11:12:54PM +0100, Giorgio Dal Molin wrote:
> Hi all,
>
> I'm trying to add board code for an am335x based HW project.
> I had a look at similar boards like 'boards/phytec-som-am335x'
> or 'boards/beaglebone'.
> I understand that I need two images: the (little) MLO and the
> (bigger) barebox.
>
> What it's not really clear is how the MLO loads and starts the
> barebox.
See arch/arm/mach-omap/xload.c. It is compiled when no shell is enabled
(I think at least for clarity there should be a separate Kconfig
symbol). In this file omap_xload() detects where the SoC has booted from
and loads the full barebox from the same source.
>
> Moreover I saw there's always a call to:
>
> am33xx_save_bootinfo((void *)bootinfo);
>
> in the MLO lowlevel entry function; I suspect the argument
> 'bootinfo' is the register r0 left by the function __barebox_arm_head()
> but I cannot really understand the logic behind it.
When the am335x ROM passes control to the bootloader then it passes in
R0 a pointer to the bootinfo. This is a three word structure which has
informations where the SoC has booted from. In am33xx_save_bootinfo() we
copy the information to a known place where we can pick it up later, see
am33xx_bootsource().
Sascha
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next prev parent reply other threads:[~2018-02-16 7:52 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-02-13 22:12 Giorgio Dal Molin
2018-02-14 5:11 ` Alexander Shiyan
2018-02-16 7:51 ` Sascha Hauer [this message]
2018-02-16 9:15 ` Giorgio Dal Molin
2018-02-19 6:28 ` Sascha Hauer
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