Lower CPU frequency on imx8mm

daisukeyoshinar — Wed, 23 Oct 2019 08:15:29 GMT

Hello

I am using the latest release 4.9.98_2.0.0 on iMX 8M Mini EVK.
I want to set the CPU frequency lower than 400MHz.

I changed dtis file.

~/imx-yocto-bsp/build-xwayland/tmp/work-shared/imx8mmevk/kernel-source/arch/arm64/boot/dts/freescale/fsl-imx8mm.dtis

&A53_0 {
   operating-points = <
       /* kHz    uV */
       1800000 1000000
       1600000 950000
       1500000 950000
       1300000 950000
       1200000 850000
       1000000 850000
       800000 850000
       600000 850000
       400000 850000
       200000 850000
       100000 850000
       10000 850000
   >;

Twelve operating points are recognized.

root@imx8mmevk:/sys/devices/system/cpu/cpu0/cpufreq# cat scaling_available_frequencies
10000 100000 200000 400000 600000 800000 1000000 1200000 1300000 1500000 1600000 1800000

Switching from 1.8GHz to 600MHz is possible.
However, the following error occurs when the frequency is set to 400 MHz or lower.

root@imx8mmevk:/sys/devices/system/cpu/cpu0/cpufreq# echo 400000 > scaling_setspeed
[ 2553.146119] cpu cpu0: failed to set clock rate: -16
[ 2553.339631] cpufreq: __target_index: Failed to change cpu frequency: -16

Where can I change it to 400MHz or lower?

In addition, when I made the same change and used the IMX8MQ-evk board, I confirmed that it can be set to 400MHz or less.

Best regards,
Daisuke Yoshinari

Re: Lower CPU frequency on imx8mm

Bio_TICFSL — Thu, 24 Oct 2019 16:33:48 GMT

Hello Daisuke,

This patch from the BSP team, which adds the lower frequency points to the MX8MM.

This is the note that came along with it:

"The 8MQ and 8MM uses different PLL, the 8MM’s 1416 PLL does NOT have 400MHz in rate table; here is a patch for it."

Regards

Re: Lower CPU frequency on imx8mm

daisukeyoshinar — Fri, 25 Oct 2019 02:19:19 GMT

Thank you very much for your reply.

After applying the patch, it became 400MHz or less.

Best regards,
Daisuke Yoshinari

Re: Lower CPU frequency on imx8mm

gnulux — Fri, 14 Oct 2022 09:34:27 GMT

Hello ,

Does this patch can be applied to IMXM Plus SOC too ?

Rgds

i.MX ProcessorsのトピックLower CPU frequency on imx8mm

Lower CPU frequency on imx8mm

Re: Lower CPU frequency on imx8mm

Re: Lower CPU frequency on imx8mm

Re: Lower CPU frequency on imx8mm