Hi Dmitry,
It's only for Realtek devices.
If Realtek device firmware receives SET_FEATURE(device remote wakeup) usb cmd during usb is suspending, it will remains in suspend state.
Otherwise, firmware will drop itself and device will consume less power. But when host resumes, it needs to reload firmware. It can be accomplished by setting usb reset resume for device.
Thanks,
BRs.
> Subject: Re: [PATCH v2] Bluetooth: btusb: Fix suspend issue for Realtek devices
>
> On Mon, Aug 12, 2019 at 9:36 AM Marcel Holtmann <[email protected]>
> wrote:
> >
> > Hi Alex,
> >
> > > From the perspective of controller, global suspend means there is no
> > > SET_FEATURE (DEVICE_REMOTE_WAKEUP) and controller would drop
> the
> > > firmware. It would consume less power. So we should not send this kind
> > > of SET_FEATURE when host goes to suspend state.
> > > Otherwise, when making device enter selective suspend, host should
> send
> > > SET_FEATURE to make sure the firmware remains.
> > >
> > > Signed-off-by: Alex Lu <[email protected]>
> > > ---
> > > drivers/bluetooth/btusb.c | 34 ++++++++++++++++++++++++++++++---
> -
> > > 1 file changed, 30 insertions(+), 4 deletions(-)
> >
> > this one doesn’t apply cleanly to bluetooth-next. Can you please send a
> version that does.
>
> Is this a chip issue or system issue? I.e. if in some system BT
> controller is wired so that it loses power over system suspend, this
> is quite different form chip itself losing firmware in certain
> situations, and this smells like a system issue and thus needs to be
> addressed on system level.
>
> Thanks.
>
> --
> Dmitry
>
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