[PATCH v3 2/3] phy: qcom-snps-femto-v2: add system sleep PM ops

[Adrien Thierry]

Writing another email to not muddy the waters in the previous email.

I discovered that the femto PHY PM count doesn't seem to be right. Even
when the dwc3 core runtime suspends and calls
phy_pm_runtime_put_sync(dwc->usb2_generic_phy) [1], the count equals 1
after that and the PHY is not runtime suspended.

This is because on boot, the count is incremented twice because
phy_power_on() is called twice:

First:
phy_power_on+0x120/0x184
dwc3_core_init+0x68c/0xda4
dwc3_probe+0xc84/0x1304

Second:
phy_power_on+0x120/0x184
usb_phy_roothub_power_on+0x48/0xa0
usb_add_hcd+0x94/0x604
xhci_plat_probe+0x4bc/0x6e4
xhci_generic_plat_probe+0xa0/0x104

That makes the femto PHY runtime PM impossible to test at the moment. I'm
not sure if this should be fixed on the dwc3 side or the xhci side, but
this should probably be a topic for another patch series.

Best,

Adrien

[1] https://elixir.bootlin.com/linux/latest/source/drivers/usb/dwc3/core.c#L2005