Problem with reducing power consumption at i.MX6q

[ivannikolaenko]

Hi all!

I am trying to implement steps (5.1.4 of https://cache.freescale.com/files/32bit/doc/app_note/AN4509.pdf ) for reduce CPU clock but meet with problems.

1. I do not have /sys/devices/platform/imx_busfreq.0 entry (CONFIG_ARM_IMX6Q_CPUFREQ enabled). It means that BUSFREQ driver not loading and I don't understand why.

2. There are only two available frequencies in the /sys/devices/system/cpu/cpu0/cpufreq :

/sys/devices/system/cpu/cpu0/cpufreq# cat scaling_available_frequencies

792000 996000

3. How to automatically re-mount SD rootfs after exit from "echo mem > /sys/power/state" state?

Please help me resolve this issues.

My linux kernel is 3.14.52 from Yocto (Jethro branch). Processor is i.MX6Q, SabreSD-based custom board.

Thank you.

[Yuri]

Hello,

  According to Chapter 24 (Dynamic Bus Frequency Driver) of “i.MX_Linux_Reference_Manual.pdf”,

the Bus Frequency drivers is included and enabled by default.

To Enable the bus frequency driver use the following command:

$ echo 1 > /sys/bus/platform/drivers/imx6_busfreq/busfreq.13/enable

http://www.nxp.com/webapp/Download?colCode=L3.14.52_1.1.0_LINUX_DOCS&Parent_nodeId=13376994810717061...

As for working points of CPUFREQ, please check Your DTS file :

arch/arm/boot/dts/imx6q.dtsi 

Have a great day,
Yuri

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