From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id E2C8FC001DF for ; Wed, 2 Aug 2023 14:57:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234221AbjHBO5n (ORCPT ); Wed, 2 Aug 2023 10:57:43 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50640 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233961AbjHBO5i (ORCPT ); Wed, 2 Aug 2023 10:57:38 -0400 Received: from us-smtp-delivery-162.mimecast.com (us-smtp-delivery-162.mimecast.com [170.10.133.162]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 024EE134 for ; Wed, 2 Aug 2023 07:56:49 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=hp.com; s=mimecast20180716; t=1690988208; 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cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.6631.45; Wed, 2 Aug 2023 14:56:43 +0000 Received: from SJ0PR84MB2088.NAMPRD84.PROD.OUTLOOK.COM ([fe80::8cd0:b5a5:f173:60f7]) by SJ0PR84MB2088.NAMPRD84.PROD.OUTLOOK.COM ([fe80::8cd0:b5a5:f173:60f7%6]) with mapi id 15.20.6609.032; Wed, 2 Aug 2023 14:56:43 +0000 From: "Gagniuc, Alexandru" To: Alan Stern CC: "linux-usb@vger.kernel.org" , "netdev@vger.kernel.org" , "davem@davemloft.net" , "edumazet@google.com" , "kuba@kernel.org" , "pabeni@redhat.com" , "hayeswang@realtek.com" , "jflf_kernel@gmx.com" , "bjorn@mork.no" , "svenva@chromium.org" , "linux-kernel@vger.kernel.org" , "Zhang, Eniac" , "stable@vger.kernel.org" Subject: Re: [PATCH v2] r8152: Suspend USB device before shutdown when WoL is enabled Thread-Topic: [PATCH v2] r8152: Suspend USB device before shutdown when WoL is enabled Thread-Index: AQHZumfGWALIKL1Qf0uRlSRmGE3IR6/BawiAgBXCwgU= Date: Wed, 2 Aug 2023 14:56:43 +0000 Message-ID: References: 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X-MS-Exchange-CrossTenant-Network-Message-Id: 467dabf2-1995-4d99-c33f-08db9368afac X-MS-Exchange-CrossTenant-originalarrivaltime: 02 Aug 2023 14:56:43.6237 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: ca7981a2-785a-463d-b82a-3db87dfc3ce6 X-MS-Exchange-CrossTenant-mailboxtype: HOSTED X-MS-Exchange-CrossTenant-userprincipalname: f4v2qF4lTAx+16/qTPifYz4ZjfvO5rclUf3ZaM7PjGgpnAsOId6HHrCK20olFdS5W6EhDMlWdY20l/Bi7kRNra7/B972SGecnYCrumhcPVQ= X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM3PR84MB3468 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: hp.com Content-Language: en-US Content-Type: text/plain; charset=WINDOWS-1252 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jul 19, 2023 at 02:36:25PM -0400, Alan Stern wrote:=0A> On Wed, Jul= 19, 2023 at 05:37:56PM +0000, Alexandru Gagniuc wrote:=0A> > For Wake-on-L= AN to work from S5 (shutdown), the USB link must be put=0A> > in U3 state. = If it is not, and the host "disappears", the chip will=0A> > no longer resp= ond to WoL triggers.=0A> >=20=0A> > To resolve this, add a notifier block a= nd register it as a reboot=0A> > notifier. When WoL is enabled, work throug= h the usb_device struct to=0A> > get to the suspend function. Calling this = function puts the link in=0A> > the correct state for WoL to function.=0A>= =20=0A> How do you know that the link will _remain_ in the correct state?= =0A=0AThe objective is to get to xhci_set_link_state() with the USB_SS_PORT= _LS_U3=0Aargument. This is achieved through usb_port_suspend() in drivers/u= sb/host/hub.c,=0Aand the function is implemented in drivers/usb/host/xhci-h= ub.c.=0A=0AThis is the only path in the kernel that I am aware of for setti= ng the U3 link=0Astate. Given that it is part of the USB subsystem, I am fa= irly confident it will=0Ashow consistent behavior across platforms.=0A=20= =0A> That is, how do you know that the shutdown processing for the USB host= =20=0A> controller won't disable the link entirely, thereby preventing WoL = from=20=0A> working?=0A=0AWe are talking to the USB hub in order to set the= link state. I don't see how=0Aspecifics of the host controller would influ= ence behavior. I do expect a=0Acontroller which advertises S4/S5 in /proc/a= cpi/wakeup to not do anything that=0Awould sabotage this capability. Disabl= ing the link entirely would probalby=0Aviolate that promise.=0A=0AThink of = USB-C docks with a power button showing up as a HID class. The scenario=0Ah= erein would disable the power button. I would take that to be a bug in the = host=0Acontroller driver if the S4/S5 capability is advertised.=0A=0AAlex= =0A=0AP.S. I sincerely apologize for the delay in my reply. The corporate e= mail servers here=0Ahave "difficulties" with plaintext and interleaved rep= lies.=0A