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

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Date:   Fri, 3 Jan 2020 10:24:36 -0800
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Al Cooper <alcooperx@...il.com>, linux-kernel@...r.kernel.org
Cc:     Kishon Vijay Abraham I <kishon@...com>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Florian Fainelli <f.fainelli@...il.com>,
        "maintainer:BROADCOM BCM7XXX ARM ARCHITECTURE" 
        <bcm-kernel-feedback-list@...adcom.com>,
        Srinath Mannam <srinath.mannam@...adcom.com>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        "moderated list:BROADCOM BCM7XXX ARM ARCHITECTURE" 
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v4 04/13] phy: usb: Add "wake on" functionality

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@...il.com>

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