[PATCH v3 2/4] usb: aspeed-vhub: fix remote wakeup failure in iKVM use case

Neal Liu neal_liu at aspeedtech.com
Mon Dec 20 13:22:50 AEDT 2021

> -----Original Message-----
> From: Benjamin Herrenschmidt <benh at kernel.crashing.org>
> Sent: Tuesday, December 14, 2021 10:36 AM
> To: Neal Liu <neal_liu at aspeedtech.com>; Felipe Balbi <balbi at kernel.org>;
> Greg Kroah-Hartman <gregkh at linuxfoundation.org>; Joel Stanley
> <joel at jms.id.au>; Andrew Jeffery <andrew at aj.id.au>; Cai Huoqing
> <caihuoqing at baidu.com>; Tao Ren <rentao.bupt at gmail.com>; Julia Lawall
> <julia.lawall at inria.fr>; kernel test robot <lkp at intel.com>; Sasha Levin
> <sashal at kernel.org>; linux-usb at vger.kernel.org; linux-kernel at vger.kernel.org;
> linux-arm-kernel at lists.infradead.org; linux-aspeed at lists.ozlabs.org
> Cc: BMC-SW <BMC-SW at aspeedtech.com>
> Subject: Re: [PATCH v3 2/4] usb: aspeed-vhub: fix remote wakeup failure in
> iKVM use case
> On Thu, 2021-12-09 at 02:37 +0000, Neal Liu wrote:
> > I'm confused. Signaling Wakeup when wakeup_en is set if it has any ep
> > activities is not exactly what you said?
> >
> > wakeup_en is set only if host allows this device have wakeup
> > capability and bus being suspended.
> >
> > Normal ep activities would not write the MMIO because wakeup_en is not
> > set.
> Hrm... I didn't think wakeup_en was limited to the bus being suspended, but
> maybe I misremember, it's been a while.
> Cheers,
> Ben.

wakeup_en is only set in the case of host set USB_DEVICE_REMOTE_WAKEUP feature to vhub devices.
I think this behavior only occurs during host is going to suspend, and set this feature to any device which can wakeup itself before sleep.


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