Make CPU frequency on imx6s unchangable

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Make CPU frequency on imx6s unchangable

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alexanderhoppus
Contributor I

I want to make CPU frequency on imx6s based board unchangeable. Even WFI call shouldn't affect. So far I observe the  CPU frequency cut off during processor stays in WFI mode.

According to technical reference manual for imx6s the low power mode, the processor will be transfered after WFI, is configured by LPM bits of CLPCR register (page 855). I have set LPM bits to 0x0 what is mentioned as RUN mode. From my understanding this should be enough not to put processor in any kind of sleep mode (WAIT or STOP on imx).

Is there something else behind this? Am i missing something here?

When I set mask bit for masking cpu0 WFI in CLPCR it didn't help too.  i.e. after WFI instruction CPU clocks are shutdowned. Why?

Suppose I use non-linux custom environment. I dont have any kind of DVFS in my system!

Thank you.

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Bio_TICFSL
NXP TechSupport
NXP TechSupport

HI Alexander,

Setup in Low power modes depends on DVFS and DPTC drivers. The device tree shows how they are modified, however, when you are moving into low power modes the DVFS basically is the one handling the Clock to perform a change in the frequency when the voltage decreases.

CCM_REF_EN_B signal is controlled by software (manually) via CCM_CLPCR[dis_ref_osc] bit,
in case when an external oscillator is applied, assuming on-chip oscillator (CCM_CLPCR[SBYOS])
functionality is bypassed. If  on-chip oscillator is used instead of the external one, CCM_REF_EN_B
behavior is described in CCM_CLPCR [SBYOS] field description.

Regards

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alexanderhoppus
Contributor I

Hello!.

From my question: "Suppose I use non-linux custom environment. I dont have any kind of DVFS in my system!"

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