FREQUENCY SPEED ( imX6SX)

[abelussi]

Two questions concerning p/n MCIMX6X4AVM08AB, we use in an application:

1. We expected that this uC had a maximum core speed of 800MHz, as the part number refers to a Cortex-A9 speed of 800MHz. However, we verified that the core frequency often rose automatically up to 1GHz from 800MHz, likely according to the work load. If this is an expected behavior of this uC, what are the limitations on its operating core frequency? According to application needs, can core  be forced to work to a frequency over 800MHz?

1. During thermal tests on the application, uC junction temperature reached 112°C, under specific operating conditions. In this case, we did not observe any automatic reduction of core frequency, unlike p/n MCIMX6X4EVM10AB, which we could verify that at a junction temperature of about 93°C reduced core speed down to 200MHz. Is it correct? Must SW limit core speed over a specific junction temperature in case of uC p/n MCIMX6X4AVM08AB?

Thanks in advanced

[Yuri · Accepted solution]

@abelussi 
Hello,

1.
You are right - MCIMX6X4AVM08AB is qualified to work till 800 MHz of CPU.
Please try using the recent NXP Linux BSP L5.4.47

https://www.nxp.com/design/software/embedded-software/i-mx-software/embedded-linux-for-i-mx-applicat...

Use section 2.5.3 [CPU Frequency Scaling (CPUFREQ)] of the Linux Manual.

< https://www.nxp.com/docs/en/reference-manual/IMX_REFERENCE_MANUAL.pdf >

For CPU frequency working point settings, see the SoC corresponding dtsi file in arch/arm/boot/dts:

https://source.codeaurora.org/external/imx/linux-imx/tree/arch/arm/boot/dts/imx6sx.dtsi?h=imx_5.4.47...

For Your device - in order to be fully on safe side - it is required to remove the following
points:

operating-points = <
/* kHz uV */
996000 1250000

fsl,soc-operating-points = <
/* ARM kHz SOC uV */
996000 1175000

2.
Use section 2.9 (Thermal) of the Linux Manual regarding thermal considerations.
Check kernel configuration if thermal option is present:

Device Drivers > Generic Thermal sysfs driver > Temperature sensor driver for i.MX SoCs.

Regards,
Yuri.

[abelussi]

Thanks Yuri

About the second question:

2.9.4 Menu Configuration Options
In menu configuration enable the following module:
• For i.MX6 and i.MX7: Device Drivers > Generic Thermal sysfs driver > Temperature sensor driver for i.MX SoCs.

In the attached file which menu item of "Linux/x86 4.9.67 Kernel Configuration", corresponds to Temperature sensor driver for i.MX SoCs.

Thanks

[marcocavallini]

The option is CONFIG_IMX_THERMAL and is set as static (=y) in .config

&cpu0 {
operating-points = <
/* kHz uV */
// REMOVE 996000 1250000
792000 1175000
396000 1175000
198000 1175000
>;
fsl,soc-operating-points = <
/* ARM kHz SOC uV */
// REMOVE 996000 1250000
792000 1175000
396000 1175000
198000 1175000
>;
fsl,arm-soc-shared = <1>;
};

[Yuri]

@abelussi 
Hello,

  is Your Linux BSP from NXP?

Regards,
Yuri.

[abelussi]

It's from the link: https//github.com/Freescale/fsl-community-bsp-platfrom -b zeus

[Yuri]

@abelussi 
Hello,

   perhaps it makes sense to use NXP Linux:

https://www.nxp.com/design/software/embedded-software/i-mx-software/embedded-linux-for-i-mx-applicat...

Regards,
Yuri.