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

[Neal Liu]

> -----Original Message-----
> From: Neal Liu
> Sent: Thursday, December 2, 2021 11:03 AM
> To: Benjamin Herrenschmidt <benh at kernel.crashing.org>; 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 2/3] usb: aspeed-vhub: support remote wakeup feature
> 
> > -----Original Message-----
> > From: Benjamin Herrenschmidt <benh at kernel.crashing.org>
> > Sent: Wednesday, December 1, 2021 7:38 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
> > Subject: Re: [PATCH 2/3] usb: aspeed-vhub: support remote wakeup
> > feature
> >
> > On Tue, 2021-11-30 at 09:47 +0000, Neal Liu wrote:
> > > > Should this  be controlled by d->wakeup_en ? IE, we have a feature
> > > > for the host to enable/disable remote wakeup, should we honor it ?
> > >
> > > For KVM usage, remote keyboard packet would be sent if user wants to
> > > do
> > remote wakeup.
> > > In this case, d->wakeup_en is not used.
> > > Set VHUB_CTRL_AUTO_REMOTE_WAKEUP to enable HW automatically
> > signaling
> > > wakeup if any packet would be transferred.
> >
> > Sorry, I don't fully understand your explanation here.
> >
> > Normally, a USB device will do remote wakeup if it's instructed to do
> > so via the appropriate feature being set, which is what wakeup_en
> > reflects. I hadn't originally plumbed it in, I forgot why, I think
> > something was either not properly documented or not working when I wrote
> that driver.
> >
> > You seem to want to override the behaviour and always send a remote
> > wakeup packet no matter what. I am not sure this is desirable for all
> > use cases, and might be something we want to make configurable, no ?
> >
> > I'm trying to understand your sentence, you seem to imply that the
> > only use case here is "KVM" (as in remote USB on a server system)
> > which I can probably agree with... mostly.
> >
> > And you say in that case, we should always do remote wakeup whenever
> > an emulated USB device has any activity (keyboard or otherwise),
> > regardless of whether the server has enabled the feature or not.
> >
> > Am I correct ? What's the rationale here ?
> >
> > Cheers,
> > Ben.
> >
> 
> Let's me describe more details for our hardware behavior and hope you
> understand.
> 
> HUB00[4]: MANUAL_REMOTE_WAKEUP
> HUB00[3]: AUTO_REMOTE_WAKEUP

Correct bit number.

> 
> 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
> 
> -Neal

I also have another solution which you might be more acceptable without enabling HUB00[3].
I think I will resent this patch if you preferred.

diff --git a/drivers/usb/gadget/udc/aspeed-vhub/epn.c b/drivers/usb/gadget/udc/aspeed-vhub/epn.c
index 99b0a12d4dc0..1e0ac742c29b 100644
--- a/drivers/usb/gadget/udc/aspeed-vhub/epn.c
+++ b/drivers/usb/gadget/udc/aspeed-vhub/epn.c
@@ -400,6 +400,11 @@ static int ast_vhub_epn_queue(struct usb_ep* u_ep, struct usb_request *u_req,
        } else
                u_req->dma = 0;

+       if (ep->dev->wakeup_en) {
+               EPVDBG(ep, "Wakeup host first\n");
+               ast_vhub_hub_wake_all(vhub);
+       }
+
        EPVDBG(ep, "enqueue req @%p\n", req);
        EPVDBG(ep, " l=%d dma=0x%x zero=%d noshort=%d noirq=%d is_in=%d\n",
               u_req->length, (u32)u_req->dma, u_req->zero,

Thanks

-Neal