From: Yi Qingliang <niqingliang2003@gmail.com>
To: Juergen Beisert <jbe@pengutronix.de>
Cc: barebox@lists.infradead.org
Subject: Re: about s3c2442
Date: Thu, 10 Jan 2013 17:45:10 +0000 [thread overview]
Message-ID: <1982990.BKj08KPbd8@yiqingliang-pc> (raw)
In-Reply-To: <201301101014.08015.jbe@pengutronix.de>
On Thursday, January 10, 2013 10:14:07 AM Juergen Beisert wrote:
> Hi Yi,
>
> Yi Qingliang wrote:
> > On Thursday, January 10, 2013 09:36:36 AM Juergen Beisert wrote:
> > > Yi Qingliang wrote:
> > > > I'm using barebox (based on mini2440) on my s3c2442 board,
> > > >
> > > > 1. flash barebox into nand: can't start normally, but can see early
> > > > output on serial.
> > > > 2. load it in sdram: can start normally into shell, and then I use it
> > > > to boot kernel (also in sdram, also based on mini2440).
> > > > the kernel hang, no output.
> > > >
> > > > after dig into it, I found something: add "mem=64M" into the kernel
> > > > paramer, then the kernel can start.
> > > >
> > > > BUT:
> > > > the barebox doesn't pass that paramert to kernel for mini2440,
> > > > why the mini2440 kernel can start normally?
> > > >
> > > > how does the kernel on 2440 get the sdram size?
> > >
> > > There is no autodetection possible. Take a look into
> > > the "arch/arm/boards/friendlyarm-mini2440/lowlevel_init.S": This is the
I found it,
but:
md 0x48000028
48000028: 000000b2 (represents is 128)
it looks like the lowlevel_init is not executed, what's the problem.
> > > code which runs immediately after reset. It calls the
> > > function "s3c24x0_sdram_init" from the generic part, and uses hard coded
> > > values from "arch/arm/boards/friendlyarm-mini2440/config.h" to setup the
> > > SDRAM controller according to the attached SDRAM type.
> > > When the SDRAM is up and running, it is very easy to read back the SDRAM
> > > size from the SDRAM controller's registers (which is done in the
> > > function "s3c24xx_get_memory_size").
> > >
> > > So you need routines which do the same job for your S3C2442 CPU.
> >
> > and the kernel? how does the kernel know the sdram size for mini2440?
> > read the cpu register set by barebox?
>
> No. The bootloader forwards this information to the kernel as an ATAG or via
> device tree. But this can only work, if also the bootloader knows the
> correct SDRAM size!
>
> Regards,
> Juergen
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next prev parent reply other threads:[~2013-01-10 9:46 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-01-10 15:07 Yi Qingliang
2013-01-10 8:36 ` Juergen Beisert
2013-01-10 9:08 ` Yi Qingliang
2013-01-10 9:14 ` Juergen Beisert
2013-01-10 17:45 ` Yi Qingliang [this message]
2013-01-10 10:00 ` Juergen Beisert
2013-01-10 19:14 ` Yi Qingliang
2013-01-10 11:20 ` Juergen Beisert
2013-01-10 17:54 ` Yi Qingliang
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