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How to indicate whether the Linux system of AM3358 is shut down?

user4575812
Prodigy 30 points
Other Parts Discussed in Thread: AM3358, TPS65910

I have a need, that is,  I want to turn off the external power,after the Linux system of AM3358  is shuted down. Does AM3358 have such an instruction?such as the hardware IO .

  • 0
    TI__Guru**** 393215 points
    This could be the PMIC_POWER_EN signal. See section 20.3.3.8 in the AM335X Technical Reference Manual Rev. L. Note that this pin operates at 1.8V logic levels.
  • 0 in reply to Biser Gatchev-XID
    Prodigy 30 points

    Will this pin chang from 1 to 0 , when the system is turned off ? But we didn't see any change of this pin,when we enter a command as "shut down" or "power off".

  • 0 in reply to Biser Gatchev-XID
    Prodigy 30 points
    Hi Biser,
    We did some test on AM335X GPEVM, if we used halt or shutdown commands,the Linux would shutdown,however left the PMIC output still available. The pmic_power_en pin is kept high throughout the shutdown process. We had to manually shut down the power of TPS65910 by the switch.
    However, the product we design,is excepcted to shut down the PMIC automatically after the Linux system shutting down thoroughly. The control pin may be from software controlled hardware pin, like pmic_power_en. However, we don't succeeded in handing this on the GPEVM.
    Could you help to point out whether current design on AM335X GPECM could meet our needs? If yes, what else do we need to change or modified?
  • 0 in reply to user4575812
    TI__Guru**** 161600 points
    Hi,

    Here is what I found, when I tested this on my BBB using TPS65217C:

    1. As Biser suggested you can monitor the pmic_power_en pin to indicate when Linux is shut down. When you power up the board pmic_power_en goes high. When you execute "poweroff" the pin goes low after the following kenrel messages:
    [ 487.348052] musb-hdrc musb-hdrc.1.auto: USB bus 1 deregistered
    [ 487.357361] reboot: Power down
    [ 487.360512] System will go to power_off state in approx. 1 second
    2. When you execute the poweroff command all the LDO outputs also stop. The most obvious indicator for this is the power led D1 connected to VLDO2; it goes off.

    I am not well familiar with the TPS65910, but if the poweroff command is not suitable in your case, you can use the I2C interface to send a command to shut down the pmic. I.e. play with the i2c commands in u-boot to read/write in the TPS65910 registers (to shut down the pmic).

    Hope this helps.

    Best Regards,
    Yordan