LKML Archive on lore.kernel.org
help / color / mirror / Atom feed
From: Alan Stern <stern@rowland.harvard.edu>
To: Mathias Nyman <mathias.nyman@intel.com>
Cc: Sneeker Yeh <sneeker.yeh@gmail.com>,
	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: Thu, 12 Feb 2015 10:18:19 -0500 (EST)	[thread overview]
Message-ID: <Pine.LNX.4.44L0.1502121013390.1209-100000@iolanthe.rowland.org> (raw)
In-Reply-To: <54DCAF88.4010607@intel.com>

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?

> Would it make sense to check those bits in xhci_enqueue_urb, and just return error
> in the xhci_urb_enqueue() if device is not connected? Then there wouldn't be a need for any quirk
> at all.

That wouldn't help URBs that were already enqueued when the disconnect 
occurred.

Alan Stern


  reply	other threads:[~2015-02-12 15:18 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 [this message]
2015-02-13  8:54       ` Mathias Nyman
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

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=Pine.LNX.4.44L0.1502121013390.1209-100000@iolanthe.rowland.org \
    --to=stern@rowland.harvard.edu \
    --cc=Sneeker.Yeh@tw.fujitsu.com \
    --cc=andy.green@linaro.org \
    --cc=balbi@ti.com \
    --cc=devicetree@vger.kernel.org \
    --cc=galak@codeaurora.org \
    --cc=grant.likely@linaro.org \
    --cc=gregkh@linuxfoundation.org \
    --cc=ijc+devicetree@hellion.org.uk \
    --cc=jaswinder.singh@linaro.org \
    --cc=kishon@ti.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-omap@vger.kernel.org \
    --cc=linux-usb@vger.kernel.org \
    --cc=mark.rutland@arm.com \
    --cc=mathias.nyman@intel.com \
    --cc=pawel.moll@arm.com \
    --cc=ray.huang@amd.com \
    --cc=robh+dt@kernel.org \
    --cc=sneeker.yeh@gmail.com \
    --subject='Re: [PATCH v3 1/5] xhci: add a quirk for device disconnection errata for Synopsis Designware USB3 core' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).