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From: Mathias Nyman <mathias.nyman@linux.intel.com>
To: Alan Stern <stern@rowland.harvard.edu>,
	Mathias Nyman <mathias.nyman@intel.com>,
	Sneeker Yeh <sneeker.yeh@gmail.com>
Cc: Rob Herring <robh+dt@kernel.org>, Pawel Moll <pawel.moll@arm.com>,
	Mark Rutland <mark.rutland@arm.com>,
	Ian Campbell <ijc+devicetree@hellion.org.uk>,
	Kumar Gala <galak@codeaurora.org>, Felipe Balbi <balbi@ti.com>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Grant Likely <grant.likely@linaro.org>,
	Huang Rui <ray.huang@amd.com>,
	Kishon Vijay Abraham I <kishon@ti.com>,
	devicetree@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-usb@vger.kernel.org, linux-omap@vger.kernel.org,
	Andy Green <andy.green@linaro.org>,
	Jassi Brar <jaswinder.singh@linaro.org>,
	Sneeker Yeh <Sneeker.Yeh@tw.fujitsu.com>
Subject: Re: [PATCH v3 1/5] xhci: add a quirk for device disconnection errata for Synopsis Designware USB3 core
Date: Fri, 13 Feb 2015 10:54:08 +0200	[thread overview]
Message-ID: <54DDBBB0.7070602@linux.intel.com> (raw)
In-Reply-To: <Pine.LNX.4.44L0.1502121013390.1209-100000@iolanthe.rowland.org>

On 12.02.2015 17:18, Alan Stern wrote:
> On Thu, 12 Feb 2015, Mathias Nyman wrote:
> 
>> On 25.01.2015 10:13, Sneeker Yeh wrote:
>>> This issue is defined by a three-way race at disconnect, between
>>> 1) Class driver interrupt endpoint resheduling attempts if the ISR gave an ep
>>>    error event due to device detach (it would try 3 times)
>>> 2) Disconnect interrupt on PORTSC_CSC, which is cleared by hub thread
>>>    asynchronously
>>> 3) The hardware IP was configured in silicon with
>>>    - DWC_USB3_SUSPEND_ON_DISCONNECT_EN=1
>>>    - Synopsys IP version is < 3.00a
>>> The IP will auto-suspend itself on device detach with some phy-specific interval
>>> after CSC is cleared by 2)
>>>
>>> If 2) and 3) complete before 1), the interrupts it expects will not be generated
>>> by the autosuspended IP, leading to a deadlock. Even later disconnection
>>> procedure would detect that corresponding urb is still in-progress and issue a
>>> ep stop command, auto-suspended IP still won't respond to that command.
> 
> If the Synopsys IP provides a way to do it, it would be better to turn
> off the autosuspend feature entirely.  Doesn't autosuspend violate the
> xHCI specification?
> 
>> So did I understand correctly that the class driver submits a new urb which
>> is enqueued by xhci_urb_enqueue() before the hub thread notices the device is disconnected.
>> Then hub thread clears CSC bit, controller suspends and the new urb is never given back?
>>
>> Doesn't the CSC bit and PORT_CONNECT bit show the device is disconnected when we enter
>> xhci_enqueue_urb(), even it the hub thread doesn't know this yet?
> 
> What if the device disconnects _after_ the new URB is enqueued?

True, those URBs would be left hanging.

So if possible, tweaking the Synopsis autosuspend feature would be nicer.

If its not possible then I guess a quirk patch like this will do.

-Mathias


 




  reply	other threads:[~2015-02-13  8:53 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-01-25  8:13 [PATCH v3 0/5] Add support for Fujitsu USB host controller Sneeker Yeh
2015-01-25  8:13 ` [PATCH v3 1/5] xhci: add a quirk for device disconnection errata for Synopsis Designware USB3 core Sneeker Yeh
2015-02-12 13:50   ` Mathias Nyman
2015-02-12 15:18     ` Alan Stern
2015-02-13  8:54       ` Mathias Nyman [this message]
2015-02-15 15:09       ` Sneeker Yeh
2015-02-15 14:29     ` Sneeker Yeh
2015-02-16  9:26       ` Mathias Nyman
2015-02-13  9:08   ` Mathias Nyman
2015-01-25  8:13 ` [PATCH v3 2/5] xhci: Platform: Set Synopsis device disconnection quirk based on platform data Sneeker Yeh
2015-01-25  8:13 ` [PATCH v3 3/5] usb: dwc3: add revision number DWC3_REVISION_290A and DWC3_REVISION_300A Sneeker Yeh
2015-01-25  8:13 ` [PATCH v3 4/5] usb: dwc3: Add quirk for Synopsis device disconnection errata Sneeker Yeh
2015-01-25  8:13 ` [PATCH v3 5/5] usb: dwc3: add Fujitsu Specific Glue layer Sneeker Yeh
2015-01-27 15:22 ` [PATCH v3 0/5] Add support for Fujitsu USB host controller Felipe Balbi
2015-01-29 16:23   ` Felipe Balbi
2015-01-30 16:38     ` Felipe Balbi
2015-02-10 15:43       ` Sneeker Yeh
2015-02-11 11:57         ` Mathias Nyman

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