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AM623: Linux SDK Standby feature

Koichiro Tashiro
Mastermind 22945 points
Part Number: AM623


Tool/software:

Hi,

Standby mode is supported in Linux SDK version 11.1.
My customer understood the Standby Mode is automatically handled by the Linux CPUIdle framework.
So when there is nothing to do, the device goes to standby mode. It is fine for most of usecases.

The customer does not want to put the device into standby under specific system conditions even there is nothing to do by CPU.
Is this possible to disable standby mode entry temporarily? 
The specific system condition can be determined by Linux application.

Thanks and regards,
Koichiro Tashiro

  • 0
    TI__Guru**** 171131 points

    Hi Tashiro-san,

    root@am62xx-evm:~# ls /sys/devices/system/cpu/cpu0/cpuidle/state*/
    /sys/devices/system/cpu/cpu0/cpuidle/state0/:
    above  below  default_status  desc  disable  latency  name  power  rejected  residency  time  usage

    /sys/devices/system/cpu/cpu0/cpuidle/state1/:
    above  below  default_status  desc  disable  latency  name  power  rejected  residency  s2idle  time  usage

    echo 1 to the entry "disable" listed above should disable the corresponding cpuidle state. echo 0 to it should enable it.

  • 0 in reply to Bin Liu
    TI__Mastermind 22945 points

    Hi Bin,

    Thanks for your quick reply.
    The customer has two questions for your answer.
    Q1) It seems default values for "disable" are '0' for both state0 and state1.

    root@am62xx-lp-evm:/sys/devices/system/cpu/cpu0/cpuidle/state0# cat disable
0
root@am62xx-lp-evm:/sys/devices/system/cpu/cpu0/cpuidle/state1# cat disable
0

    Is this expected and below action need to be taken to enable Standby Mode?
    root@am62xx-lp-evm:# echo 1 > /sys/devices/system/cpu/cpu0/cpuidle/state0/disable
root@am62xx-lp-evm:# echo 1 > /sys/devices/system/cpu/cpu0/cpuidle/state1/disable


    Q2) What is difference between state0 and state1?
    Any document available?

    Thanks and regards,
    Koichiro Tashiro

  • 0 in reply to Koichiro Tashiro
    TI__Guru**** 171131 points

    Hi Tashiro-san,

    Koichiro Tashiro said:
    Q1) It seems default values for "disable" are '0' for both state0 and state1.

    Sorry I messed it up in my original response. It should be that "echo 1" to disable, and "echo 0" to enable, since the sysfs entry name is "disable".

    I have corrected this in my response above.

    Koichiro Tashiro said:
    Q2) What is difference between state0 and state1?

    The "name" entry in the sysfs tells the function of each state.

    root@am62xx-evm:~# cat /sys/devices/system/cpu/cpu0/cpuidle/state*/name
    WFI
    stby

    So, state0 is "WFI", state1 is Standby mode defined in kernel devicetree k3-am62x-sk-lpm-standby.dtso.

    Koichiro Tashiro said:
    Any document available?

    The only information I found is the kernel devicetree binding doc in the kernel source:

    Documentation/devicetree/bindings/cpu/idle-states.yaml