From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
        id S1751360AbdKIPRK (ORCPT <rfc822;w@1wt.eu>);
        Thu, 9 Nov 2017 10:17:10 -0500
Received: from mail.kernel.org ([198.145.29.99]:60078 "EHLO mail.kernel.org"
        rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP
        id S1750991AbdKIPRJ (ORCPT <rfc822;linux-kernel@vger.kernel.org>);
        Thu, 9 Nov 2017 10:17:09 -0500
DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 051E6218EB
Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=kernel.org
Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=dinguyen@kernel.org
Subject: Re: Suspend to disk with usb connected fails to detect usb(reset)
 during resume
To: Ivid Suvarna <ivid.suvarna@gmail.com>,
        Alan Stern <stern@rowland.harvard.edu>
Cc: USB list <linux-usb@vger.kernel.org>, balbi@kernel.org,
        gregkh@linuxfoundation.org, Billy Araujo <billyaraujo@gmail.com>,
        johnyoun@synopsys.com, Felipe Balbi <felipe.balbi@linux.intel.com>,
        Kernel development list <linux-kernel@vger.kernel.org>,
        Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
        Oliver Neukum <oneukum@suse.com>, Johan Hovold <johan@kernel.org>,
        Michal Nazarewicz <mina86@mina86.com>,
        Vincent Pelletier <plr.vincent@gmail.com>,
        Jerry Zhang <zhangjerry@google.com>, John Keeping <john@metanate.com>,
        Krzysztof Opasiak <k.opasiak@samsung.com>,
        Abdulhadi Mohamed <abdulahhadi2@gmail.com>,
        Matthew Wilcox <willy@linux.intel.com>,
        Janusz Dziedzic <januszx.dziedzic@linux.intel.com>
References: <CABXF_ABR4XbUqOmmxwZGZUAqmJ=e_aUYa=4oMn653tWyZxvYBA@mail.gmail.com>
 <Pine.LNX.4.44L0.1711071047300.1395-100000@iolanthe.rowland.org>
 <CABXF_ADHJB-Q+Di+iG5SxXcReP-4p0zeQK9ehqD=oH4ad89SEg@mail.gmail.com>
From: Dinh Nguyen <dinguyen@kernel.org>
Message-ID: <4ff09187-7ee7-78d0-82e2-bb3f763f181f@kernel.org>
Date: Thu, 9 Nov 2017 09:17:05 -0600
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101
 Thunderbird/52.4.0
MIME-Version: 1.0
In-Reply-To: <CABXF_ADHJB-Q+Di+iG5SxXcReP-4p0zeQK9ehqD=oH4ad89SEg@mail.gmail.com>
Content-Type: text/plain; charset=utf-8
Content-Language: en-US
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org



On 11/08/2017 06:29 AM, Ivid Suvarna wrote:
> On Tue, Nov 7, 2017 at 9:19 PM, Alan Stern <stern@rowland.harvard.edu> wrote:
>> On Tue, 7 Nov 2017, Ivid Suvarna wrote:
>>
>>> Hi,
>>>
>>> I am trying to support suspend to disk(hibernate) on Hikey with 4.4
>>> kernel. During suspend, I could see the usb devices getting reset and I
>>> can access them properly. Message can be seen as below:
>>>
>>> usb 1-1: reset high-speed USB device number 2 using dwc2
>>> usb 1-1.2: reset high-speed USB device number 3 using dwc2
>>> usb 1-1.2.4: reset high-speed USB device number 4 using dwc2
>>
>> You might start by asking why the devices need to be reset during
>> suspend.  I can't see any reason for doing this.
>>
>> Alan Stern
>>
> 
> Yes please. Could you explain as to why the usb needs to reset while
> suspending?
> This scenario is also observed in normal suspend to ram.
> 
> And why the USB gets disconnected on resume from hibernation.
> I checked the register dump of usb in /sys/kernel/debug and all
> registers after resume have zero value.
> 

Registers with zero value is indicative of a clock not getting turned
on, at least that I have encountered with DWC2 on the SoCFPGA platform.

Dinh