[U-Boot] U-boot and linux command line parameters

[U-Boot] U-boot and linux command line parameters

[Mirek23]

Dear All,

I use linux kernel 2.6.23 and u-boot 1.2.0 (on ppc405 virtex-4 ) for  some
time. All works fine when the
kernel together with initramfs is smaller than 8MB. If it is bigger than the
kernel does not boot properly.

First of all I would like to know how the address for the linux command line
parameters is "transferred" from u-boot to linux for ppc405 (virtex4 chip)?
(via some registers or is it  a fixed address in the memory ie. 8MB?)
Does somebody know what should be changed, in the kernel,  in order to move
this limitation from 8MB to let say 12MB? I would be grateful for any hint.

Thanks in advance.
M. 
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[U-Boot] U-boot and linux command line parameters

[Mirek23]

When studying the u-boot (1.2.0) source code I have found that 
it is  register r6 and r7 which pass the location of the command line
parameters and the
size. 

The location of the parameters could be changed in u-boot according to the
macro:
CFG_BOOTMAPSZ

There is however the message in all configuration files for u-boot that
Linux can only map first initial 8MB
so it seems to be not possible to set CFG_BOOTMAPSZ to something higher than
8MB?

/*
 * For booting Linux, the board info and command line data
 * have to be in the first 8 MB of memory, since this is
 * the maximum mapped by the Linux kernel during initialization.
 */
#define CFG_BOOTMAPSZ             (8 << 20)   /* Initial Memory map for
Linux */
 

Does somebody have an idea how to bypass this limitation in linux 2.6.23 or
higher?

M.


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[U-Boot] U-boot and linux command line parameters

[Wolfgang Denk]

Dear Mirek23,

In message <23703431.post@talk.nabble.com> you wrote:
> 
> When studying the u-boot (1.2.0) source code I have found that 
> it is  register r6 and r7 which pass the location of the command line
> parameters and the
> size. 

This has also been pointed out on the ML in reply to your request.

It has also been pointed out that U-Boot 1.2.0 is very old. Please
update and use recent code; we don't want to spend time on such
obsolete code any more.

Best regards,

Wolfgang Denk

-- 
DENX Software Engineering GmbH,     MD: Wolfgang Denk & Detlev Zundel
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd at denx.de
Of all possible committee reactions to any  given  agenda  item,  the
reaction  that will occur is the one which will liberate the greatest
amount of hot air.                                -- Thomas L. Martin

[U-Boot] U-boot and linux command line parameters

[Mirek23]

Dear Wolfgang,

In fact the problem which I have pointed out is not on the u-boot side but
in linux kernel which 
can only accept command line parameters in first 8MB of RAM. 

Was this limitation somehow changed? Is there a different mechanism for
passing command line parameters from  u-boot to linux (in u-boot version
1.3.4 versus 1.2.0) (for ppc405 architecture).

Best Regards

Mirek




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[U-Boot] U-boot and linux command line parameters

[Wolfgang Denk]

Dear Mirek23,

In message <23704724.post@talk.nabble.com> you wrote:
> 
> Was this limitation somehow changed? Is there a different mechanism for
> passing command line parameters from  u-boot to linux (in u-boot version
> 1.3.4 versus 1.2.0) (for ppc405 architecture).

Current U-Boot and Linux versions use the device tree to pass such
information.

And note that U-Boot 1.3.4 is pretty old, too. When I wrote "use
recent code" I really meant it - i. e. use v2009.06-rc2 or at least
v2009.03.

Best regards,

Wolfgang Denk

-- 
DENX Software Engineering GmbH,     MD: Wolfgang Denk & Detlev Zundel
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd at denx.de
Cleverness and Style have no place in getting a project completed.
                                                  -- Tom Christiansen

[U-Boot] U-boot and linux command line parameters

[Mirek23]

Dear Wolfgang,

Thank you for your answer. I understand that it is best to use the latest
version of u-boot and linux kernel but the pair u-boot 1.2.0 and linux
2.6.23 I can relay on. I have already tried in the past u-boot 1.3.4 and
kernel 2.6.29 and I had the problem to get the IP address using the DHCP
server (on the u-boot level). 
I have given up with the newer version of u-boot and I am still using this
what works for me.
(This is however a different subject)

As regards the limitation of 8MB I have done some experiments and it seems
to be that it is not a problem any more. I have described that under the
link:
 
http://www.nabble.com/U-boot-and-linux-command-line-parameters-td23698384.html

Basically the CFG_BOOTMAPSZ could be set to 16 MB:
#define CFG_BOOTMAPSZ             (8 << 21)  /* 16 MB */ 

Best Regards

Mirek

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