disabling 2 cores on the iMX6 quad core sabresd board?

[abraham_v]

We are planning to use the dual core iMX6 chip on our target board (end product will be running android OS). For development we got the quad core iMX6 sabresd board. Is there any way to disable 2 processor cores on that board?

On another matter - with the exception of the extra cores, can I assume that the iMX6 dual and quad core processors are identical? Or is there anything specific I need to watch out for? From the wording in the reference manual, they look identical to me.

[abraham_v]

Thanks guys! I'll checkout your suggestions tomorrow and report back afterwards. :smileyhappy:

[AnsonHuang]

OK, these cores are identical, I think for your experiment, you can just add "maxcpus=2" in command line for testing. And for you product, you can get our Dual core version i.MX6D.

Also, you can "echo 0 > /sys/device/system/cpu/cpuX/online" (X is 2 or 3) to remove one core. echo "1" is to add them back.

BTW, if you think this question is answered, please help close it, thanks in advanced!

[abraham_v]

Took me awhile to find the exact location were the kernel command line arguments were being set. But, yes, your suggestion of 'maxcpus=2' works. Thanks AnsonHuang ! :smileyhappy:

-Abraham V.

[santhoshbatthin]

Hi Abraham,

Can you tell where is the location for kernel command line arguments.

--Santhosh B

[AnsonHuang · Accepted solution]

When you boot up kernel, just add maxcpus=2 in command line, kernel will only boot two CPUs.

Also, you can cut the VDDARM23_IN, and config the menu config to support two cores and rebuild kernel.

[krishnanair]

AnsonHuang‌

Hi,

We are also having a similar issue of VDDARM23_IN leakage current for Dual core. While going through the reference manual, we saw an option to Power-Gate the cores 2,3 by setting fusemap configurations (Fuse address: 0x4D0[31]). 

Is it possible to disable the 2 cores in this manner also? Or do we need to additionally run the maxcpus=2 command in the kernel. ?

[santhoshbatthin]

Hi Yongsai,

I am a newbie to linux. Could you please guide me how to set maxcpus=2 in kernel command line arguments and also where to cut VDDARM23_IN.

My requirement is to load one OS in each core. Could you please guide how to do this?

Thanks in advance.

Regards,

Santhosh B

[RandyKrakora]

I got this info a while back:

On a Linux machine you can get the CPU information from /proc/cpuinfo file. On a dual core machine, you will get the output like this:

$ cat /proc/cpuinfo

processor : 0

vendor_id : GenuineIntel

........

.....

processor : 1

vendor_id : GenuineIntel

........

.....

To disable a core run the following command on a Ubuntu machine:

$ sudo sh -c "echo 'n' > /sys/devices/system/cpu/cpu1/online"

Test if the core is disabled or not, check the /proc/cpuinfo file.

$ cat /proc/cpuinfo

processor : 0

vendor_id : GenuineIntel