[U-Boot] How to silence the output of U-Boot

[Frank Ihle]

Hi everyone,

I searched the Internet but the help I found didn't work. I hope someone here may know how to fix it, here's the situation:

I have this ARM9 SAM9G25 which is accessed by its ttyS0. I
 want to disable all of the output, that was made during the U-Boot (v. 2010.06) 
boot, to decrease the CPU's load. Therefore there is the 


  setenv silent 1



parameter, which i put into the BOOTCMD string like:



  #define CONFIG_BOOTCOMMAND   " setenv silent 1;" \

"bootm "



and there is (as mentioned in the Readme.silent http://git.denx.de/cgi-bin/gitweb.cgi?p=u-boot.git;a=blob;f=doc/README.silent;hb=v2013.10 ) the
#define CONFIG_SILENT_CONSOLE
#define CONFIG_SYS_DEVICE_NULLDEV
#define CONFIG_SILENT_CONSOLE_UPDATE_ON_SET


command, neither one is working (the lines printed out are still the same and the boot time didn't change). Whereas the 
         setenv verify n
is working, just to give an example.

Does somebody see the error ?

BTW
 (I'm not sure if this is related to this) in the referenced link there 
is the information, that u-boot sets the kernel command line to 
"console=" so that in the end there will be no output for the kernel 
too, but that didn't happen and it doesn't even happen if i force to 
boot Linux with "console=" in the default Linux command line string
Thanks for your help.
Kind Regards,
Frank