linux-kernel - Re: [RFC RESEND PATCH 0/1] USB EHCI: repeated resets on full and low speed devices

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Message-ID: <4d1ab90a-ec55-85e8-d646-cfa58f08d449@oracle.com>
Date:   Tue, 1 Sep 2020 11:00:16 -0600
From:   Khalid Aziz <khalid.aziz@...cle.com>
To:     Alan Stern <stern@...land.harvard.edu>
Cc:     gregkh@...uxfoundation.org, erkka.talvitie@...cit.fi,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC RESEND PATCH 0/1] USB EHCI: repeated resets on full and low
 speed devices

On 9/1/20 10:36 AM, Alan Stern wrote:
> On Tue, Sep 01, 2020 at 09:15:46AM -0700, Khalid Aziz wrote:
>> On 8/31/20 8:31 PM, Alan Stern wrote:
>>> Can you collect a usbmon trace showing an example of this problem?
>>>
>>
>> I have attached usbmon traces for when USB hub with keyboards and mouse
>> is plugged into USB 2.0 port and when it is plugged into the NEC USB 3.0
>> port.
> 
> The usbmon traces show lots of errors, but no Clear-TT events.  The 
> large number of errors suggests that you've got a hardware problem; 
> either a bad hub or bad USB connections.

That is what I thought initially which is why I got additional hubs and
a USB 2.0 PCI card to test. I am seeing errors across 3 USB controllers,
4 USB hubs and 4 slow/full speed devices. All of the hubs and slow/full
devices work with zero errors on my laptop. My keyboard/mouse devices
and 2 of my USB hubs predate motherboard update and they all worked
flawlessly before the motherboard upgrade. Some combinations of these
also works with no errors on my desktop with new motherboard that I had
listed in my original email:

2. USB 2.0 controller - WORKS
5. USB 3.0/3.1 controller -> Bus powered USB 2.0 hub - WORKS

I am not seeing a common failure here that would point to any specific
hardware being bad. Besides, that one code change (which I still can't
say is the right code change) in ehci-q.c makes USB 2.0 controller work
reliably with all my devices.

--
Khalid