No console output when booting linux from uboot

Qin, Laigui (GE EntSol, Security) laigui.qin at
Fri Jun 6 21:54:05 EST 2008

Sorry for the confusing. I just figured out my problem is not for the
Uboot version...

As you suggested, I debuged the hw action related to serial driver
today. I add the "console=ttyS2" in my uboot bootargs and corrected some
part, but still no output yet. Is there other factors will affect the
console output, except the serial driver?

Mike Qin

-----Original Message-----
From: at
[ at] On
Behalf Of Detlev Zundel
Sent: Thursday, June 05, 2008 10:22 PM
To: linuxppc-embedded at
Subject: Re: No console output when booting linux from uboot

Hi Mike,

> Thanks. Now I am confusing with the way uboot passing parameters to 
> linux kernel:
> in Uboot 1.2.0: Kernel is entered through the following calling
>         theKernel (linux_argc, linux_argv, linux_env, 0); while in 
> Uboot 1.3.0:
>         (*kernel) (kbd, initrd_start, initrd_end, cmd_start, cmd_end);
> The linux kernel I used is designed with Uboot 1.2.0, while I used 
> 1.3.2. Will this be a problem for passing the parameters?

Hm, now you got me confused.  I cannot see the first version anywhere in
u-boot or its history.  Even in 1.2.0 its either

(*kernel) (kbd, initrd_start, initrd_end, cmd_start, cmd_end);


(*kernel) ((bd_t *)of_flat_tree, (ulong)kernel, 0, 0, 0);

The first path is chosen when using the traditional 2 argument bootm
command, the logic being that this is a non-fdt aware kernel.  The
second path is chosen when using the newer three-argument version of
bootm with the third argument being the flat device tree (needs
CONFIG_OF_FLAT_TREE in U-Boot 1.2.0).

So if you have anything differing from this, you have to conclude for
yourself what the situation is.  When you have mainline U-Boot and
Linux, i.e. comparable what I describe, we especially took care that we
are backwards compatible.  So by using the two- or three parameter
version, we effectively select between two kernel call conventions.  The
situation stays the same in newer U-Boot versions.


DENX Software Engineering GmbH,      MD: Wolfgang Denk & Detlev Zundel
HRB 165235 Munich,  Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-40 Fax: (+49)-8142-66989-80 Email: dzu at

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