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NVME SSD Power Control Manager


The package mantains for SSD power control and related noification handle Deamon


 The service power supply design follow PCI Express Card Electromechanical Specification Revision 3.0 in Section 2.2

 nvme_gpio.service follow section 2.2.1 Initial power-Up to initinal and adjust related signal.

 nvme_powermanager.service follow section 2.2.2 power management states monitor PRESENT signal and update related signal.


* Plugging
    1. U2_[SSD_index] PRSNT_N will be input low
    2. Set PWR_U2_[SSD_index]_EN to high
    3. Check PWRGD_U2_[SSD_index] is high
    4-1. If PWRGD_U2_[SSD_index] is high (PWR Good)
	    - Wait 5ms
	    - Enable PCI Clock by SMBus 9FGL0851
	    - Wait 100ms
        - Set RST_BMC_U2 to high

    4-2. If PWRGD_U2_[SSD_index] is low (PWR Fail)
	    - Set RST_BMC_U2_[SSD_index]_R_N to low
        - Wait 100ms
        - Disable PCI Clock by SMBus

* Removing
    1. U2_[SSD_index] PRSNT_N will be input high
    2. Set RST_BMC_U2 to low
    3. Wait 100ms
    4. Disable PCI Clock by SMBus
    5. Wait 5ms
    6. PWR_U2_[SSD_index]_EN to low


1. PRESENT detect SSD: The hardware design has been implemented.
2. Initial SSD slot Power output: nvme_gpio service has tested on Module. It could sucess initial gpios and set correct power output.
3. Detect PRESENT and change power setting: nvme_powermanager service has tested on Module. It could success detect SSD plugged or removal change power output.
4. Improve initial power-up sequence: For matched hardware default initial power-up setting, the nvme_gpio service only set unplugged slot related signal.
5. Improve service execute sequence: nvme_powermanager.service must wait for nvme_gpio.service ensure gpio export complete.