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

From: Neal Liu <neal_liu@aspeedtech.com>
To: Benjamin Herrenschmidt <benh@kernel.crashing.org>,
	Felipe Balbi <balbi@kernel.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Joel Stanley <joel@jms.id.au>, Andrew Jeffery <andrew@aj.id.au>,
	Cai Huoqing <caihuoqing@baidu.com>,
	Tao Ren <rentao.bupt@gmail.com>,
	Julia Lawall <julia.lawall@inria.fr>,
	kernel test robot <lkp@intel.com>,
	Sasha Levin <sashal@kernel.org>,
	"linux-usb@vger.kernel.org" <linux-usb@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"linux-arm-kernel@lists.infradead.org" 
	<linux-arm-kernel@lists.infradead.org>,
	"linux-aspeed@lists.ozlabs.org" <linux-aspeed@lists.ozlabs.org>
Cc: BMC-SW <BMC-SW@aspeedtech.com>
Subject: RE: [PATCH v3 2/4] usb: aspeed-vhub: fix remote wakeup failure in iKVM use case
Date: Mon, 27 Dec 2021 02:07:02 +0000	[thread overview]
Message-ID: <HK0PR06MB3202796B4DDF471856149B1480429@HK0PR06MB3202.apcprd06.prod.outlook.com> (raw)
In-Reply-To: <HK0PR06MB3202051E7C15E84006DF55C0807B9@HK0PR06MB3202.apcprd06.prod.outlook.com>

> -----Original Message-----
> From: Neal Liu
> Sent: Monday, December 20, 2021 10:23 AM
> To: Benjamin Herrenschmidt <benh@kernel.crashing.org>; Felipe Balbi
> <balbi@kernel.org>; Greg Kroah-Hartman <gregkh@linuxfoundation.org>; Joel
> Stanley <joel@jms.id.au>; Andrew Jeffery <andrew@aj.id.au>; Cai Huoqing
> <caihuoqing@baidu.com>; Tao Ren <rentao.bupt@gmail.com>; Julia Lawall
> <julia.lawall@inria.fr>; kernel test robot <lkp@intel.com>; Sasha Levin
> <sashal@kernel.org>; linux-usb@vger.kernel.org; linux-kernel@vger.kernel.org;
> linux-arm-kernel@lists.infradead.org; linux-aspeed@lists.ozlabs.org
> Cc: BMC-SW <BMC-SW@aspeedtech.com>
> Subject: RE: [PATCH v3 2/4] usb: aspeed-vhub: fix remote wakeup failure in
> iKVM use case
> 
> > -----Original Message-----
> > From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
> > Sent: Tuesday, December 14, 2021 10:36 AM
> > To: Neal Liu <neal_liu@aspeedtech.com>; Felipe Balbi
> > <balbi@kernel.org>; Greg Kroah-Hartman <gregkh@linuxfoundation.org>;
> > Joel Stanley <joel@jms.id.au>; Andrew Jeffery <andrew@aj.id.au>; Cai
> > Huoqing <caihuoqing@baidu.com>; Tao Ren <rentao.bupt@gmail.com>; Julia
> > Lawall <julia.lawall@inria.fr>; kernel test robot <lkp@intel.com>;
> > Sasha Levin <sashal@kernel.org>; linux-usb@vger.kernel.org;
> > linux-kernel@vger.kernel.org; linux-arm-kernel@lists.infradead.org;
> > linux-aspeed@lists.ozlabs.org
> > Cc: BMC-SW <BMC-SW@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.
> Thanks
> 
> -Neal
> 
Would you like to test it if you have some free time.
Please feel free for any feedback.

-Neal