Re: [PATCH v4 04/13] phy: usb: Add "wake on" functionality

From: Florian Fainelli
Date: Fri Jan 03 2020 - 13:24:48 EST

On 1/3/20 10:18 AM, Al Cooper wrote:
> Add the ability to handle USB wake events from USB devices when
> in S2 mode. Typically there is some additional configuration
> needed to tell the USB device to generate the wake event when
> suspended but this varies with the different USB device classes.
> For example, on USB Ethernet dongles, ethtool should be used to
> enable the magic packet wake functionality in the dongle.
> NOTE: This requires that the "power/wakeup" sysfs entry for
> the USB device generating the wakeup be set to "enabled".
> This functionality requires a special hardware sideband path that
> will trigger the AON_PM_L2 interrupt needed to wake the system from
> S2 even though the USB host controllers are in IDDQ (low power state)
> and most USB related clocks are shut off. For the sideband signaling
> to work we need to leave the usbx_freerun clock running, but this
> clock consumes very little power by design. There's a bug in the
> XHCI wake hardware so only EHCI/OHCI wake is currently supported.
> Signed-off-by: Al Cooper <alcooperx@xxxxxxxxx>

Reviewed-by: Florian Fainelli <f.fainelli@xxxxxxxxx>