[PATCH 2/3] usb: aspeed-vhub: support remote wakeup feature

Benjamin Herrenschmidt benh at kernel.crashing.org
Mon Dec 6 11:08:42 AEDT 2021

On Thu, 2021-12-02 at 03:03 +0000, Neal Liu wrote:
> > 
> Let's me describe more details for our hardware behavior and hope you
> understand.
> Set HUB00[3] implies USB device will do remote wakeup if any write
> command to vhub register.
> Set HUB00[4] implies USB device will do remote wakeup. It can only be
> set in suspend state.
> For current design, d->wakeup_en only controls whether HUB00[4] can
> be set through usb_gadget_ops.wakeup().
> If some applications (take KVM as example) want to wakeup host by
> sending a packet, it won't go through sb_gadget_ops.wakeup().
> We enable HUB00[3] to fix this problem. It won't override above
> mentioned behavior.
> If host has enabled the USB_DEVICE_REMOTE_WAKEUP feature, it has 2
> ways to wakeup host.
> 1. set srp 1 (/sys/device/platform/xxxxxxxxx/udc/xxxxxx/srp)
> 2. emulated device has activity
> If host has disabled the USB_DEVICE_REMOTE_WAKEUP feature, these 2
> ways still cannot wakeup host even if USB bus is in resume state.
> Thanks

So what you are saying is that currently, the various gadgets aren't
calling usb_gadget_wakeup() ?

Ie. it should be a gadget policy to decide when to wake-up I suppose,
but it's true that nothing in the core nor the existing gadgets seem to
handle that.

I think what you propose is a band-aid. The real problem is that the
gadget drivers should trigger wakeups (or the core should do so on

That said, for now, I don't object to adding that "auto" bit, but I
would prefer if that behaviour was use configurable.


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