About changing the default CPU frequency in i.MX6DQ.

[keitanagashima]

Dear All,

Hello. I have a question about changing the CPU frequency.

Now, my customer is using jb4.2.2_1.1.0 and default CPU freq is 792MHz.

We want to change the CPU freq from 792MHz to 996MHz.

We tried to change the kernel parameter from arm_freq=800 to arm_freq=1000.

But, Warning log was repeated.

- COULD NOT SET SOC VOLTAGE BACK!!!!

- COULD NOT SET PU VOLTAGE!!!!

The error was outputted at the function of "function set_cpu_freq" under 'kernel_imx/src/arch/arm/plat-mxc/cpufreq.c'.

Maybe, it looks internal LDOs setting error.

[Question]

How should one change the CPU freq in U-boot?

Best Regards,

Keita

[Yuri]

Hello,

The Android is based on i.MX 6Quad BSP L3.0.35_4.0.0 GA release.

According to Table 6 (Kernel Boot Parameters) of the “Linux Release Notes”,

by defaut, LDO bypass is enabled, assuming that external PMIC should supply

VDDARM_IN/VDDSOC_IN power rail. But looks like in Your case PMIC is absent.
   “If you want to use internal LDO, please specify " ldo_active=on" to the kernel

command line”.

Have a great day,
Yuri

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[keitanagashima]

Dear Yuri,

Hello. Thank you for your reply.

>by defaut, LDO bypass is enabled, assuming that external PMIC should supply

>VDDARM_IN/VDDSOC_IN power rail. But looks like in Your case PMIC is absent.
>   “If you want to use internal LDO, please specify " ldo_active=on" to the kernel

>command line”.

We checked the PMU_REG_CORE register and confirmed LDO enabled.

But, the error occurred.

[Q1]

Is my understanding right?

- By the setting of arm_freq=1000, automatically, the voltage of LDO isn't changed.

[Q2]

How should one change the CPU freq and LDO voltage?

Best Regards,

Keita

[Yuri · Accepted solution]

Hello,

  By default the CPU FREQ is enabled and it makes sense to control frequency via

proper governor after Linux boot. In this sense the kernel boot parameter as “arm_freq=1000”

does not make sense.

Regards,

Yuri.