VDD_ARM behavior in Low power mode

[dhanaraj_d]

Hi

When imx7d Processor put in low power mode using "mem" writing to /sys/power/state, due to DVFS feature we are getting increased in VDD_ARM voltage also. My doubt is we should see current also and measure power(which is reduced in low power mode since current consuming is less even voltage increased) or voltage must be low?

[igorpadykov]

Hi Dhanaraj

this depends on software, for example one can look at

sect.4.1. Low-power mode use cases for VDD_ARM behaviour:

i.MX 7DS Power Consumption Measurement

On the other hand it can be "ON/OFF" according to Table 14. Power modes

i.MX 7Dual Family of Applications Processors Datasheet

Best regards
igor
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[dhanaraj_d]

Hi Igor,

Thank you for your reply.

We no need to turn off VDD_ARM supply. From power consumption document understood that when doing Dhrystone benchmarking usecase, voltage is increased. But my doubt is without doing any stress on cpu and simply entering deep sleep mode will cause voltage change? I measured current is reduced that time any way. 

[igorpadykov]

Hi Dhanaraj

>But my doubt is without doing any stress on cpu and simply entering deep sleep

>mode will cause voltage change?

one can look at sect.4.1.1. Use case 1: Deep-Sleep Mode (DSM)

i.MX 7DS Power Consumption Measurement

it shows VDD_ARM value.

Best regards
igor

[dhanaraj_d]

Hi Igor,

Ok Thank you.

So it should be low voltage(0.974) but in board which am having, getting near to 1.07 V. Is there any step to see while entering deep sleep mode to reduce voltage? 

[igorpadykov]

Hi Dhanaraj

what bsp used in the case, one can try with nxp official linux

from source.codeaurora.org/external/imx repository

linux-imx - i.MX Linux kernel 

Best regards
igor

[dhanaraj_d]

Hi Igor,

We got code from sumo branch, 

https://source.codeaurora.org/external/imx/imx-manifest -b imx-linux-sumo -m

[igorpadykov]

Hi Dhanaraj

could you try to reproduce issue on NXP i.MX7D EVK reference board.

For custom board one can debug it using sect.2.5.1 Low Level Power Management (PM)

attached Linux Manual.

Best regards
igor

[dhanaraj_d]

Hi Igor,

Can you please attach that linux Manual.

[igorpadykov]

Hi Dhanaraj

one can find it in Linux L4.14.98_2.0.0 Documentation

Best regards
igor