How to use only 1 processor

Hi,

I've been trying to recompile U-Boot so that Ubuntu only uses 1 processor.
Unfortunately
setenv
wont help as there is no
saveenv
function available.

What I have been doing is adding
"maxcpus=1"
to all kinds of places without success.

Here are some of my attempts which I all applied in in the device tree (in turn, not at the same time)
/include/config/zynq_zed.h

#define CONFIG_BOOTARGS "maxcpus=1"
above "/* No NOR Flash available on ZedBoard */"

and in the section:
#define CONFIG_EXTRA_ENV_SETTINGS
I tried it below ramdisk_size (with "" at the end) and at the very end of that section (without the "").

Please tell me what I'm doing wrong.

For the sake of completness. All the resulting boot.bin boot just fine, though using both CPUs. At leas system monitor show two and they both have some load on them.

0 zedhed over 12 years ago

Hi AirLancer,

Keep in mind that bootargs passed by U-Boot are superceeded by the ones brought into the kernel via the device tree binary.

You will need to reverse engineer the DTB to DTS and modify ake a look inside of the DTS file and locate the bootargs string definition.

There are some instructions on the Xilinx wiki on how to use the device tree compiler:

http://wiki.xilinx.com/zynq-linux

For the OOB Linux demo, this string is set to the following:

bootargs = "console=ttyPS0,115200 root=/dev/ram rw initrd=0x800000,8M earlyprintk rootfstype=ext4 rootwait devtmpfs.mount=0";

If you add the term maxcpus=1 to the list of bootargs statements, that should work for what you intend to do.

Regards,

-Kevin
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0 Former Member over 12 years ago

Hey Kevin,
thanks for your answer.
With the help of the device tree tutorial:
http://www.xillybus.com/tutorials/device-tree-zynq-1
I got a better understanding of what you meant.
For those with the same problem, reading the first page of the device tree tutrial should be enough to get a .dts file from the .dtb file (and vice versa after editing).
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