topic Re: DVFS Issue on imx7dsabresd in i.MX Processors

DVFS Issue on imx7dsabresd

muhammed_ali — Mon, 24 Jun 2019 08:46:54 GMT

Hi Team,

We are facing an issue on DVFS in imx7dsabresd. we could able to measure the voltage in TP4 test point on board it always showing 1.296V on every frequency (729000,996000,1200000 Mhz). We have tested some BSP versions and It have been noticed that the issue is coming on the BSP version 4.14.98_2.0.0 and 4.14.78_1.0.0. The DVFS is working properly on 4.9.88-2.0.0_ga and L4.1.15_1.2.0 (image only). when we compare 4.9.88-2.0.0 and 4.14.98_2.0.0 we could able to find out that imx7-cpufreq.c ( drivers/cpufreq/imx7-cpufreq.c ) file is missing on 4.14.98_2.0.0 and some configuration changes. could you please help on this ?

Re: DVFS Issue on imx7dsabresd

muhammed_ali — Wed, 26 Jun 2019 04:23:50 GMT

Hi Team,

Any update on this

Re: DVFS Issue on imx7dsabresd

jamesbone — Wed, 26 Jun 2019 16:34:46 GMT

Hello Muhammed,

Can you please share your DTS file, The voltage and frequency changes are passed to the linux kernel via the u-boot dtb file. In the dts (source file for dtb). By adding or modifying the entry in the dts file, the system can work at lower frequencies.. here is what the current dts file has:

cpu0: cpu@0 {

compatible = "arm,cortex-a7";

device_type = "cpu";

reg = <0>;

operating-points = <

/* KHz uV */

996000 1075000

792000 975000

Add entries below the "792000 975000" in the dts file.

Re: DVFS Issue on imx7dsabresd

carstenhansen — Wed, 02 Oct 2019 02:36:58 GMT

imx7-cpufreq.c appears to have been replaced by the generic cpufreq-dt implementation somewhere between 4.9 and 4.14.

If you already had a working 4.9 setup, then to upgrade to 4.14 you'll likely just need to

Select CONFIG_CPUFREQ_DT and CONFIG_CPUFREQ_DT_PLATDEV in your kernel config
Fix a couple of 'undefined reference' build errors in busfreq-imx.c (those are in i.MX6 code so you can safely #ifdef the problematic code away as long as you're on i.MX7)