Is it possible to disable the A72?

[capablegh]

Hello!

One of my interest in this board is to evaluate and experiment with the RockPro64. Is it possible, and how, to disable only the A72, and use on the A53? And I would like to have the A72 disabled from power-on. One evaluation is ARM Trustzone on the board, and as the first step want to evaluate it only with the A53.

[LMM]

Hi,
the easiest way is :

# get info
cat /proc/cpuinfo
# log root
sudo -s
#disable A72 (cpu 4 & 5)
echo 0 > /sys/devices/system/cpu/cpu4/online
echo 0 > /sys/devices/system/cpu/cpu5/online
# check (ctrl-c to quit)
htop
cat /proc/cpuinfo

to enable again replace 0 by 1

---

oups I have not read that it should be from power on ! my method does not work then !

[capablegh]

Hello.

Thank you for the reply! Even if it did not exactly answer the question as I posed, it helps towards the requirement indirectly. 

You mention that the A72 CPUs show up as 4 and 5 under Linux. Is this because on power-on RK3399 has the A53s as the first CPUs always? If so then somewhere at the start of the boot sequence (e.g. Trustzone BL1 or BL2 stages) I could ensure the A72s remain in reset all the way.

---

Hi,
the easiest way is :

# get info
cat /proc/cpuinfo
# log root
sudo -s
#disable A72 (cpu 4 & 5)
echo 0 > /sys/devices/system/cpu/cpu4/online
echo 0 > /sys/devices/system/cpu/cpu5/online
# check (ctrl-c to quit)
htop
cat /proc/cpuinfo

to enable again replace 0 by 1

---

oups I have not read that it should be from power on ! my method does not work then !

[dukla2000]

Hello!

One of my interest in this board is to evaluate and experiment with the RockPro64. Is it possible, and how, to disable only the A72, and use on the A53? And I would like to have the A72 disabled from power-on. One evaluation is ARM Trustzone on the board, and as the first step want to evaluate it only with the A53.

Compile your kernel but remove the A72s from the device tree. (After boot you can assign processes to CPU etc etc but ...)

[capablegh]

Hello!

One of my interest in this board is to evaluate and experiment with the RockPro64. Is it possible, and how, to disable only the A72, and use on the A53? And I would like to have the A72 disabled from power-on. One evaluation is ARM Trustzone on the board, and as the first step want to evaluate it only with the A53.

Compile your kernel but remove the A72s from the device tree. (After boot you can assign processes to CPU etc etc but ...)

Thanks for your reply. Once Linux is booting it is too late for the Trustzone boot loaders. Like I mentioned in my previous reply, the need is for the A72 to be disabled much early so that it does not detected by the Trustzone bootloaders.

[CounterPillow]

The device trees are also used by u-boot