From: Renaud Barbier <renaud.barbier@ge.com>
To: barebox@lists.infradead.org
Subject: Re: Booting PPC Linux
Date: Fri, 02 Mar 2012 16:28:15 +0000 [thread overview]
Message-ID: <4F50F51F.5000109@ge.com> (raw)
In-Reply-To: <20120301200729.GE3852@pengutronix.de>
On 01/03/12 20:07, Sascha Hauer wrote:
> On Thu, Mar 01, 2012 at 07:41:35PM +0000, Renaud Barbier wrote:
>> I have a uImage + dtb that use to boot on a MPC8544-like system
>> a few months ago.
>>
>> After rebasing my code, it did not work.
>>
>> I notice that in arch/ppc/lib/ppclinux.c the kernel is now called
>> with the device tree as a parameter.
>>
>> After investigation, I copied the device tree to within 8MB of the
>> kernel entry point (0x0). It booted.
>>
>> Is the DTB relocation a missing step?
> Yes, it seems so. barebox holds the device tree in malloced space. This
> is likely outside 8MB of the kernel entry point. I was not aware of that
> restriction.
I think I found the limitation in Linux.
In arch/powerpc/mm/init_32.c:
/*
* address of the limit of what is accessible with initial MMU setup -
* 256MB usually, but only 16MB on 601.
*/
phys_addr_t __initial_memory_limit_addr = (phys_addr_t)0x10000000;
The book E specific code (arch/ppc/mm/fsl_booke_mmu.c) adjusts this variable
to 256MB but the highest I was able to put the DTB is below 64MB.
It may be limited by another function call.
The available memory may be limited to 8 or 16MB on other CPUs (601 and
8xx).
Thanks.
>
> Sascha
>
>
>
--
Renaud Barbier
14, Links Place
3/2 great Michael House
Edinburgh, EH67EN
Tel: +44 131 561 3532
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prev parent reply other threads:[~2012-03-02 16:28 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-03-01 19:41 Renaud Barbier
2012-03-01 20:07 ` Sascha Hauer
2012-03-02 16:28 ` Renaud Barbier [this message]
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