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From: Jesse Hathaway <jesse@mbuki-mvuki.org>
To: Alan Stern <stern@rowland.harvard.edu>
Cc: Bjorn Helgaas <helgaas@kernel.org>,
	Ingo Molnar <mingo@redhat.com>,
	Peter Zijlstra <peterz@infradead.org>,
	linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org,
	Mathias Nyman <mathias.nyman@intel.com>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	linux-usb@vger.kernel.org
Subject: Re: Regression causes a hang on boot with a Comtrol PCI card
Date: Mon, 15 Apr 2019 16:47:06 -0500	[thread overview]
Message-ID: <CANSNSoVpnK6fyfFct7cLNRJAvdLWh0ac=isnPOkOAp4LV+WoSw@mail.gmail.com> (raw)
In-Reply-To: <Pine.LNX.4.44L0.1904061121410.19196-100000@netrider.rowland.org>

On Sat, Apr 6, 2019 at 10:32 AM Alan Stern <stern@rowland.harvard.edu> wrote:
> Well, at least that's forward progress.  I don't know what pstore is or
> what connection it has to the USB subsystem.  Does the machine hang
> similarly if you boot without the Comtrol PCI card present?

Yes the box boots fine when the Comtrol PCI card is *not* present.

> For that matter, what happens if you remove EHCI from the kernel
> configuration completely?

If I remove USB support, the box still hangs after registering the pstore, but
if I remove pstore support and APEI support from the kernel then the box boots
without issue.

> As for how the PCI card affects the USB handoff, it depends on how the
> BIOS behaves.  Normally the BIOS will take control of all the available
> EHCI controllers during bootup (so that it can use them to communicate
> with a USB keyboard or mouse), including controllers on add-on PCI
> cards as well as those on the motherboard.  When the kernel starts up,
> it tries to take ownership of the controllers away from the BIOS
> (that's the handoff) so that Linux can use them.  However, if the BIOS
> was never tested for handoff of USB controllers on add-on PCI cards, it
> could easily have a bug that would crash the machine.

The Comtrol card provides 32 serial ports, via a breakout box, but it has
no USB functionality, which was why I was surprised that its presence
somehow breaks the USB hand off.

  reply	other threads:[~2019-04-15 21:47 UTC|newest]

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-03-13 16:50 Regression causes a hang on boot with a Comtrol PCI card Jesse Hathaway
2019-03-13 23:21 ` Bjorn Helgaas
2019-03-14 20:57   ` Jesse Hathaway
2019-03-21 20:36     ` Jesse Hathaway
2019-03-21 23:23     ` Bjorn Helgaas
2019-03-22 20:02       ` Jesse Hathaway
2019-04-01 19:43         ` Jesse Hathaway
2019-04-01 21:13         ` Bjorn Helgaas
2019-04-02 14:29           ` Alan Stern
2019-04-02 14:49             ` Mathias Nyman
2019-04-02 18:26               ` Alan Stern
2019-04-04 15:41             ` Jesse Hathaway
2019-04-04 17:16               ` Alan Stern
2019-04-04 17:36                 ` Jesse Hathaway
2019-04-04 19:14                   ` Alan Stern
2019-04-05 21:27                     ` Jesse Hathaway
2019-04-06 15:32                       ` Alan Stern
2019-04-15 21:47                         ` Jesse Hathaway [this message]
2019-04-16 15:00                           ` Alan Stern
2019-04-23 20:18                             ` Jesse Hathaway
2019-04-24 14:20                               ` Alan Stern

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