linux-kernel - Re: [PATCH 4.4 026/143] usb: hub: delay hub autosuspend if USB3 port is still link training

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Date:   Tue, 19 Feb 2019 10:11:30 +0200
From:   Mathias Nyman <mathias.nyman@...ux.intel.com>
To:     Alan Stern <stern@...land.harvard.edu>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Sasha Levin <sashal@...nel.org>
Subject: Re: [PATCH 4.4 026/143] usb: hub: delay hub autosuspend if USB3 port
 is still link training

On 18.2.2019 17.39, Alan Stern wrote:
> On Mon, 18 Feb 2019, Greg Kroah-Hartman wrote:
> 
>> 4.4-stable review patch.  If anyone has any objections, please let me know.
>>
>> ------------------
>>
>> [ Upstream commit e86108940e541febf35813402ff29fa6f4a9ac0b ]
>>
>> When initializing a hub we want to give a USB3 port in link training
>> the same debounce delay time before autosuspening the hub as already
>> trained, connected enabled ports.
>>
>> USB3 ports won't reach the enabled state with "current connect status" and
>> "connect status change" bits set until the USB3 link training finishes.
>>
>> Catching the port in link training (polling) and adding the debounce delay
>> prevents unnecessary failed attempts to autosuspend the hub.
>>
>> Signed-off-by: Mathias Nyman <mathias.nyman@...ux.intel.com>
>> Acked-by: Alan Stern <stern@...land.harvard.edu>
>> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
>> Signed-off-by: Sasha Levin <sashal@...nel.org>
> 
> We should be careful with this commit; it has caused problems for some
> people.  Mathias has been working to fix them, but this commit
> shouldn't go into -stable until the fixes are also ready to go.
> 

This commit should be fine, it gives ports in link training a bit more time
to finish. The commit causing issues is related, preventing runtime suspend
if ports are link training:

commit 2f31a67f01a8beb22cae754c53522cb61a005750
Author: Mathias Nyman <mathias.nyman@...ux.intel.com>
Date:   Thu Nov 15 11:38:41 2018 +0200

     usb: xhci: Prevent bus suspend if a port connect change or polling state is detected

Turns out it causes suspend issues on some MacBooks

-Mathias