No console output when booting linux from uboot

No console output when booting linux from uboot

[Qin, Laigui (GE EntSol, Security)]

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Hi all,

I am trying to boot linux kernel (2.6.23) from uboot (1.3.2) for my
custom board. The uboot works well, the kernel booting hit the
start_kernel(). But there is nothing output from console. 

With debugger, I saw that the printk() functions were called many times
without any console output. Tracing into the source code, I found that
the printk() called "con->write" operation... 

Can anyone guide me to solve this?

Mike Qin
GE Security

GE imagination at work


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Re: No console output when booting linux from uboot

[Detlev Zundel]

Hi Mike,

> I am trying to boot linux kernel (2.6.23) from uboot (1.3.2) for my custom
> board. The uboot works well, the kernel booting hit the start_kernel(). But
> there is nothing output from console.

Do you provide a correct "console=..." parameter?

> With debugger, I saw that the printk() functions were called many times without
> any console output. Tracing into the source code, I found that the printk()
> called "con->write" operation...
>
> Can anyone guide me to solve this?

I have a hint concerning an incorrect conjecture from your side.
Usually when start_kernel starts, the kernel knows nothing about
consoles to output printk messages to, so in the early phases the
printk's (like printk(KERN_NOTICE)) only end up in the internal ring
buffer.  Its only later when the console is associated with a real
device that everything gets sent there.

So you shouldn't really wonder why early printk's do not output
anything, this is a red herring.  Debug the code responsible for the hw
acting as your console according to the kernel command line.

Cheers
  Detlev

-- 
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@denx.de

RE: No console output when booting linux from uboot

[Qin, Laigui (GE EntSol, Security)]

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?


Mike Qin


-----Original Message-----
From: linuxppc-embedded-bounces+laigui.qin=3Dge.com@ozlabs.org
[mailto:linuxppc-embedded-bounces+laigui.qin=3Dge.com@ozlabs.org] On
Behalf Of Detlev Zundel
Sent: Thursday, June 05, 2008 12:31 AM
To: linuxppc-embedded@ozlabs.org
Subject: Re: No console output when booting linux from uboot

Hi Mike,

> I am trying to boot linux kernel (2.6.23) from uboot (1.3.2) for my=20
> custom board. The uboot works well, the kernel booting hit the=20
> start_kernel(). But there is nothing output from console.

Do you provide a correct "console=3D..." parameter?

> With debugger, I saw that the printk() functions were called many=20
> times without any console output. Tracing into the source code, I=20
> found that the printk() called "con->write" operation...
>
> Can anyone guide me to solve this?

I have a hint concerning an incorrect conjecture from your side.
Usually when start_kernel starts, the kernel knows nothing about
consoles to output printk messages to, so in the early phases the
printk's (like printk(KERN_NOTICE)) only end up in the internal ring
buffer.  Its only later when the console is associated with a real
device that everything gets sent there.

So you shouldn't really wonder why early printk's do not output
anything, this is a red herring.  Debug the code responsible for the hw
acting as your console according to the kernel command line.

Cheers
  Detlev

--=20
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@denx.de

_______________________________________________
Linuxppc-embedded mailing list
Linuxppc-embedded@ozlabs.org
https://ozlabs.org/mailman/listinfo/linuxppc-embedded

Re: No console output when booting linux from uboot

[Detlev Zundel]

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);

or

(*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.

Cheers
  Detlev 

--
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@denx.de

RE: No console output when booting linux from uboot

[Qin, Laigui (GE EntSol, Security)]

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=3DttyS2" 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?

BestRegards,
Mike Qin

-----Original Message-----
From: linuxppc-embedded-bounces+laigui.qin=3Dge.com@ozlabs.org
[mailto:linuxppc-embedded-bounces+laigui.qin=3Dge.com@ozlabs.org] On
Behalf Of Detlev Zundel
Sent: Thursday, June 05, 2008 10:22 PM
To: linuxppc-embedded@ozlabs.org
Subject: Re: No console output when booting linux from uboot

Hi Mike,

> Thanks. Now I am confusing with the way uboot passing parameters to=20
> linux kernel:
>
> in Uboot 1.2.0: Kernel is entered through the following calling
>         theKernel (linux_argc, linux_argv, linux_env, 0); while in=20
> 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=20
> 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);

or

(*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.

Cheers
  Detlev=20

--
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@denx.de

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Linuxppc-embedded mailing list
Linuxppc-embedded@ozlabs.org
https://ozlabs.org/mailman/listinfo/linuxppc-embedded

Re: No console output when booting linux from uboot

[Detlev Zundel]

Hi Mike,

> 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?

Actually not that I can think of.  Depending on your driver, maybe the
default baud rate is not correct?  Did you try a "console=ttyS2,115200"
for example?

Cheers
  Detlev

--
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@denx.de

Re: No console output when booting linux from uboot

[Matvejchikov Ilya]

May be console=ttyCPM0,115200 helps?

2008/6/7 Detlev Zundel <dzu@denx.de>:
> Hi Mike,
>
>> 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?
>
> Actually not that I can think of.  Depending on your driver, maybe the
> default baud rate is not correct?  Did you try a "console=ttyS2,115200"
> for example?
>
> Cheers
>  Detlev
>
> --
> 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@denx.de
>
> _______________________________________________
> Linuxppc-embedded mailing list
> Linuxppc-embedded@ozlabs.org
> https://ozlabs.org/mailman/listinfo/linuxppc-embedded
>