topic Re: Question, i.MX8M minimum CPU clock in i.MX Processors

Question, i.MX8M minimum CPU clock

SLICE — Fri, 19 Jul 2019 00:26:29 GMT

Dear team,

I would like to ask about the minimum clock speed of i.MX8M.

Could you show me what is the minimum clock speed of i.MX8M(Cortex-A53 and Cortex-M4).

The customer wants to know what numbers are available to scale down dynamically.

They think it must be related to the DDR clock.

Best Regards,

Miyamoto

Re: Question, i.MX8M minimum CPU clock

peter_tian — Fri, 19 Jul 2019 00:52:49 GMT

Hello Miyamoto,

To check the maximum frequency:
cat /sys/devices/system/cpu/*/cpufreq/cpuinfo_max_freq

To check the minimum frequency:
cat /sys/devices/system/cpu/*/cpufreq/cpuinfo_min_freq

The system automatically adjusts DDR frequency for optimal performance based on the devices that are active.

Best Regards,

Peter

Re: Question, i.MX8M minimum CPU clock

SLICE — Fri, 19 Jul 2019 02:21:53 GMT

Hello pengtian‌

I executed the command you suggested on my 8M-EVK with L4.14.78-BSP.

And the messages are as below.

Max:

1500000

Min:

1000000

Does those mean that the max speed of cortex-A53s are 1.5GHz?

And does those mean that the Min speed of cortex-A53s are 1.0GHz?

How about the min frequency of cortex-M4?

Best Regards,

Miyamoto

Re: Question, i.MX8M minimum CPU clock

peter_tian — Fri, 19 Jul 2019 06:06:37 GMT

Hello Miyamoto,

Yes. These values you got are max_freq (1.5GHz) and min_freq (1.0GHz) on i.MX8MQ-EVK + L4.14.78-BSP.

CPU (Cortex-A53) frequencies can be scaled automatically between min_freq and max_freq depending on the system load.
The target frequency of Cortex-M4 platform is 266 MHz. And there is no frequency scale function for Cortex-M4 platform.

Best Regards,

Peter

Re: Question, i.MX8M minimum CPU clock

SLICE — Fri, 19 Jul 2019 06:59:11 GMT

Hello Peter,

Thanks for your support.

Can I understand that CA53’s minimum frequency is 1.0GHz theoretically?

And CM4 cannot scale down from 266MHz.

Correct?

Best Regards,

Miyamoto

Re: Question, i.MX8M minimum CPU clock

peter_tian — Fri, 19 Jul 2019 07:46:29 GMT

Hello Miyamoto,

You can get the freq-points supported on current platform. Release BSP doesn't support others frequencies except them. Can you understand it?

cat /sys/devices/system/cpu/*/cpufreq/scaling_available_governors

CM4 core is designed at the target of 266MHz.

Best Regards,

Peter

Re: Question, i.MX8M minimum CPU clock

SLICE — Fri, 19 Jul 2019 09:10:48 GMT

Hello pengtian‌

Can I understand that min freq of CA53 is 1GHz and min freq of CM4 is 266MHZ?

We want to know the theoretical minimum freq of CA53 and CM4 to reduce power.

Best Regards,

Miyamoto

Re: Question, i.MX8M minimum CPU clock

peter_tian — Mon, 22 Jul 2019 01:10:17 GMT

Hello Miyamoto,

There is no limitation on the minimal frequency, any frequency below the target defined for the operating PVT should be supported. Customers also need to balance overall system performance and power consumption. Thanks.

Best Regards,

Peter

Re: Question, i.MX8M minimum CPU clock

SLICE — Mon, 22 Jul 2019 01:29:01 GMT

Hello Peter,

Can I understand as below?

Theoretically, the minimum frequency of CA53 and CM4 is no limitation in the terms of chip.

But the customer need to develop their own device driver for down scaling the frequency when they use the other OS than your BSPs.

Best Regards,

Miyamoto

Re: Question, i.MX8M minimum CPU clock

peter_tian — Mon, 22 Jul 2019 01:37:32 GMT

Hello Miyamoto,

Yes. Customers need to re-make their device driver to down scaling the frequency which cannot be supported by NXP release BSP. Thanks.

Best Regards,

Peter