CC'ing the author of the patch.
2013/2/18 Ronald <ronald645@xxxxxxxxx>:
>>>> This e-mail is a follow-up as requested in this bug[1]. I will repost
>>>> everything so far in this e-mail. Please CC me as I'm not subscribed
>>>> to your list.
>>>>
>>>> Current head gives this when I plug a 'Mass Storage Device' into a 2.0 hub:
>>>>
>>>> [ 842.760400] hub 1-0:1.0: unable to enumerate USB device on port 3
>>>> [ 843.080058] usb 1-3: new high-speed USB device number 48 using ehci-pci
>>>> [ 858.230072] usb 1-3: device descriptor read/64, error -110
>>>> [ 873.490070] usb 1-3: device descriptor read/64, error -110
>>>>
>>>> Reverting the following commit makes it work again:
>>>>
>>>> commit 55bcdce8a8228223ec4d17d8ded8134ed265d2c5
>>>> Author: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>
>>>> Date: Fri Jan 25 16:52:45 2013 -0500
>>>>
>>>> USB: EHCI: remove ASS/PSS polling timeout
>>>>
>>>> This patch (as1647) attempts to work around a problem that seems to
>>>> affect some nVidia EHCI controllers. They sometimes take a very long
>>>> time to turn off their async or periodic schedules. I don't know if
>>>> this is a result of other problems, but in any case it seems wise not
>>>> to depend on schedule enables or disables taking effect in any
>>>> specific length of time.
>>>>
>>>> The patch removes the existing 20-ms timeout for enabling and
>>>> disabling the schedules. The driver will now continue to poll the
>>>> schedule state at 1-ms intervals until the controller finally decides
>>>> to obey the most recent command issued by the driver. Just in case
>>>> this hides a problem, a debugging message will be logged if the
>>>> controller takes longer than 20 polls.
>>>>
>>>> I don't know if this will actually fix anything, but it can't hurt.
>>>>
>>>> Signed-off-by: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>
>>>> Tested-by: Piergiorgio Sartor <piergiorgio.sartor@xxxxxxxx>
>>>> CC: <stable@xxxxxxxxxxxxxxx>
>>>> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
>>>>
>>>> diff --git a/drivers/usb/host/ehci-timer.c b/drivers/usb/host/ehci-timer.c
>>>> index 20dbdcb..f904071 100644
>>>> --- a/drivers/usb/host/ehci-timer.c
>>>> +++ b/drivers/usb/host/ehci-timer.c
>>>> @@ -113,14 +113,15 @@ static void ehci_poll_ASS(struct ehci_hcd *ehci)
>>>>
>>>> if (want != actual) {
>>>>
>>>> - /* Poll again later, but give up after about 20 ms */
>>>> - if (ehci->ASS_poll_count++ < 20) {
>>>> - ehci_enable_event(ehci, EHCI_HRTIMER_POLL_ASS, true);
>>>> - return;
>>>> - }
>>>> - ehci_dbg(ehci, "Waited too long for the async schedule
>>>> status(%x/%x), giving up\n",
>>>> - want, actual);
>>>> + /* Poll again later */
>>>> + ehci_enable_event(ehci, EHCI_HRTIMER_POLL_ASS, true);
>>>> + ++ehci->ASS_poll_count;
>>>> + return;
>>>> }
>>>> +
>>>> + if (ehci->PSS_poll_count > 20)
>>>> + ehci_dbg(ehci, "PSS poll count reached %d\n",
>>>> + ehci->PSS_poll_count);
>>>> ehci->PSS_poll_count = 0;
>>>>
>>>> /* The status is up-to-date; restart or stop the schedule as needed */
>>>>
>>>> Please note, that I'm using the 'irqpoll' cmdline to improve system
>>>> stability. What I forgot to mention in the bug was the chipset:
>>>>
>>>> 00:10.3 USB controller: VIA Technologies, Inc. USB 2.0 (rev 82)
>>>> (prog-if 20 [EHCI])
>>>> Subsystem: Micro-Star International Co., Ltd. KT4AV motherboard
>>>> Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV+ VGASnoop- ParErr-
>>>> Stepping- SERR- FastB2B- DisINTx-
>>>> Status: Cap+ 66MHz- UDF- FastB2B- ParErr- DEVSEL=medium >TAbort-
>>>> <TAbort- <MAbort- >SERR- <PERR- INTx-
>>>> Latency: 32, Cache Line Size: 32 bytes
>>>> Interrupt: pin D routed to IRQ 21
>>>> Region 0: Memory at dffeff00 (32-bit, non-prefetchable) [size=256]
>>>> Capabilities: [80] Power Management version 2
>>>> Flags: PMEClk- DSI- D1+ D2+ AuxCurrent=375mA PME(D0+,D1+,D2+,D3hot+,D3cold+)
>>>> Status: D0 NoSoftRst- PME-Enable- DSel=0 DScale=0 PME-
>>>> Kernel driver in use: ehci-pci
>>>>
>>>> Yes, it's 10 years old, and no I'm not scrooge. We are waiting a while
>>>> for computer prices to plummet mkay?
>>>>
>>>> [1]: https://bugzilla.kernel.org/show_bug.cgi?id=54031
>>>
>>> Would like to add that while searching the mailing lists I stumbled on this:
>>>
>>> http://marc.info/?l=linux-usb&m=136045531311402&w=4
>>>
>>> It's an entirely seperate USB issue in this cycle. The person is doing
>>> git bisect to find the regression. I did another approach as
>>> recompiling the full kernel on a 1,25GHz isn't even remotely funny
>>> anymore.
>>>
>>> On top of HEAD I started reverting groups of USB EHCI patches one by
>>> one. I'm just mentioning it since I'm not sure if this procedure is
>>> accepted here.
>>
>> Did some more testing this morning. It seems like it's a race
>> condition, which somewhat confirms that this patch is involved. Just
>> had an occurance where the kernel with this patch *not* reverted
>> handled the USB just fine. But subsequent attempts failed like this:
>>
>> # attempt 2
>> [ 382.370377] hub 1-0:1.0: unable to enumerate USB device on port 3
>> [ 382.690046] usb 1-3: new high-speed USB device number 7 using ehci-pci
>> [ 397.840031] usb 1-3: device descriptor read/64, error -110
>> # attempt 3
>> [ 413.040329] hub 1-0:1.0: unable to enumerate USB device on port 3
>> [ 413.360069] usb 1-3: new high-speed USB device number 8 using ehci-pci
>> [ 428.510049] usb 1-3: device descriptor read/64, error -110
>>
>> Please note the ~15 second time-out between detection and error. This
>> also explains what made ordinary bisect somewhat 'tedious'... . Kernel
>> with this patch reverted handles the USB solidly everytime and on
>> every subsequent occurance so far.
>>
>> The 'bad' kernel handles the USB correctly every once in a while. But
>> subsequent occurances always failed so far under these conditions.
>
> One final observation, sometimes the kernel without the patch reverted
> rejects the usb-stick right away (i.e. no initial onetime success).
> Dmesg then looks like this:
>
> [ 146.980077] usb 1-3: new high-speed USB device number 4 using ehci-pci
> [ 152.140713] usb 1-3: device descriptor read/all, error -110
> [ 152.200338] hub 1-0:1.0: unable to enumerate USB device on port 3
> [ 152.520050] usb 1-3: new high-speed USB device number 6 using ehci-pci
> [ 167.670035] usb 1-3: device descriptor read/64, error -110
> [ 182.930046] usb 1-3: device descriptor read/64, error -110
> [ 183.100306] hub 1-0:1.0: unable to enumerate USB device on port 3
> [ 183.420047] usb 1-3: new high-speed USB device number 8 using ehci-pci
> [ 198.570063] usb 1-3: device descriptor read/64, error -110
> [ 213.830047] usb 1-3: device descriptor read/64, error -110
> [ 214.000248] hub 1-0:1.0: unable to enumerate USB device on port 3
> # above 4 lines repeat until stick get's unplugged
>
> Notice the first error to be related to 'read/all' and subsequent
> errors are related to 'read/64'. Kernel with patch reverted still
> works without a hitch so far.
>
> Conclusion: So I'm pretty confident this patch is the 'first bad commit'.
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