linux-kernel - Re: [PATCH v2] xhci: Set port link to RxDetect if port is not enabled after resume

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Message-Id: <635B3350-F064-4B45-B194-40F793423049@canonical.com>
Date:   Wed, 22 Apr 2020 21:21:01 +0800
From:   Kai-Heng Feng <kai.heng.feng@...onical.com>
To:     Mathias Nyman <mathias.nyman@...el.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Alan Stern <stern@...land.harvard.edu>,
        "open list:USB NETWORKING DRIVERS" <linux-usb@...r.kernel.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] xhci: Set port link to RxDetect if port is not enabled
 after resume



> On Mar 26, 2020, at 19:33, Kai-Heng Feng <kai.heng.feng@...onical.com> wrote:
> 
> Hi Mathias,
> 
>> On Mar 11, 2020, at 12:04, Kai-Heng Feng <kai.heng.feng@...onical.com> wrote:
>> 
>> On Dell TB16, Realtek USB ethernet (r8152) connects to an SMSC hub which
>> then connects to ASMedia xHCI's root hub:
>> 
>> /:  Bus 04.Port 1: Dev 1, Class=root_hub, Driver=xhci_hcd/2p, 5000M
>>   |__ Port 1: Dev 2, If 0, Class=Hub, Driver=hub/7p, 5000M
>>           |__ Port 2: Dev 3, If 0, Class=Vendor Specific Class, Driver=r8152, 5000M
>> 
>> Bus 004 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
>> Bus 004 Device 002: ID 0424:5537 Standard Microsystems Corp. USB5537B
>> Bus 004 Device 003: ID 0bda:8153 Realtek Semiconductor Corp. RTL8153 Gigabit Ethernet Adapter
>> 
>> The port is disabled after resume:
>> xhci_hcd 0000:3f:00.0: Get port status 4-1 read: 0x280, return 0x280
>> 
>> According to xHCI 4.19.1.2.1, we should set link to RxDetect to transit
>> it from disabled state to disconnected state, which allows the port to
>> be set to U0 and completes the resume process.
>> 
>> My own test shows port can still resume when it's not enabled, as long
>> as its link is in U states. So constrain the new logic only when link is
>> not in any U state.
>> 
>> Signed-off-by: Kai-Heng Feng <kai.heng.feng@...onical.com>
> 
> Do you think this is a proper fix?

Another gentle ping...

> 
> Kai-Heng
> 
>> ---
>> drivers/usb/host/xhci-hub.c | 8 ++++++++
>> 1 file changed, 8 insertions(+)
>> 
>> diff --git a/drivers/usb/host/xhci-hub.c b/drivers/usb/host/xhci-hub.c
>> index a9c87eb8951e..263f9a9237a1 100644
>> --- a/drivers/usb/host/xhci-hub.c
>> +++ b/drivers/usb/host/xhci-hub.c
>> @@ -1776,6 +1776,14 @@ int xhci_bus_resume(struct usb_hcd *hcd)
>> 			clear_bit(port_index, &bus_state->bus_suspended);
>> 			continue;
>> 		}
>> +
>> +		/* 4.19.1.2.1 */
>> +		if (!(portsc & PORT_PE) && (portsc & PORT_PLS_MASK) > XDEV_U3) {
>> +			portsc = xhci_port_state_to_neutral(portsc);
>> +			portsc &= ~PORT_PLS_MASK;
>> +			portsc |= PORT_LINK_STROBE | XDEV_RXDETECT;
>> +		}
>> +
>> 		/* resume if we suspended the link, and it is still suspended */
>> 		if (test_bit(port_index, &bus_state->bus_suspended))
>> 			switch (portsc & PORT_PLS_MASK) {
>> -- 
>> 2.17.1
>> 
>