How can I confirm how fast the Cortex-A57 and CortexA53 cores are being clocked at on my Juno board?

I believe that this early release includes no thermal protection and the CPU clock speeds are fixed and under-clocked. Currently, the SCP firmware limits the clocks to Cortex-A57 600MHz and Cortex-A53 600MHz.

The Juno Software Release Interim3 made earlier this week includes DVFS support for the CPUs with the following higher frequency operating points;

• Cortex-A57 nominal operating point of 800MHz and overdrive operating point of 1100MHz
• Cortex-A53 nominal operating point of 700MHz overdrive operating point of 850MHz

If you are using Interim3 release and have extracted the release modules.tar.bz2 on to your filesystem,

then you can have CPUFreq support.

$ lsmod | grep scpi_cpufreq

If not alredy present, try

$ modprobe scpi_cpufreq

You can read the current frequency:

$ cat /sys/devices/system/cpu/cpu<n>/cpufreq/scaling_cur_freq

where  <n> is [0 - 3] for A53 and [4 - 5] for A57(you can operate on just one cpu in the cluster)

Then you can set the governor of your choice:

$ echo $governor > /sys/devices/system/cpu/cpu<n>/cpufreq/scaling_governor

where $governor can be any one in the list below

+---------------------------------------------------------------------------------------------+

| $governor-> | powersave | performance | ondemand | userspace |

+--------------------------------------------------------------------------------------------+

| A57            | 450 MHz    |    1.1 GHz    | 450, 800, 1100 MHz    |

+--------------------------------------------------------------------------------------------+

| A53            | 450 MHz    |    850 MHz   | 450, 700, 850 MHz     |

+--------------------------------------------------------------------------------------------+

In ondemand, based on the load the governor chooses the frequency, while in userspace you can select it by:

$ echo $freq_in_khz > /sys/devices/system/cpu/cpu<n>/cpufreq/scaling_setspeed

where $freq_in_khz can be obtained from the list:

$ cat /sys/devices/system/cpu/cpu<n>/cpufreq/scaling_available_frequencies

Do you know how to change the cpufreq? do need modify SCP firmware? and, how to get the source code?  @markn   sudeep.holla                               

thanks.

[1] ARM-software/linux · GitHub