linux-kernel - Re: About the reboot hang issue with EHCI driver on the Baytrail platform

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Date:	Tue, 26 Aug 2014 11:38:52 -0400 (EDT)
From:	Alan Stern <stern@...land.harvard.edu>
To:	Gavin Guo <gavin.guo@...onical.com>
cc:	linux-usb@...r.kernel.org,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Anthony Wong <anthony.wong@...onical.com>,
	YK <yk@...onical.com>
Subject: Re: About the reboot hang issue with EHCI driver on the Baytrail
 platform

On Tue, 26 Aug 2014, Gavin Guo wrote:

> Hi,
> 
> I found that in the Baytrail-m platform if the "USB3.0 Configuration
> in Pre-OS" is set to Auto in the BIOS, the system will boot with
> EHCI-enabled. And test reboot 200 times. It sometimes hang in the
> shutdown process "ehci-pci 0000:00:1d.0: shutdown." I also found that
> sometimes hang in the booting up process. But it still black screen, I
> can't see clearly where it hang.
> 
> After doing some experiments, I found the following symptoms:
> 1) Set the "USB3.0 Configuration in Pre-OS" to enable, the 200 times
> reboot test can pass. Under the condition, lspci can't see the EHCI
> [8086:0f34] controller.
> 
> 2) Build a new kernel without the EHCI driver can also pass the 200
> times reboot test.
> 
> 3) Put "echo -n "0000:00:1d.0" > /sys/bus/pci/drivers/ehci-pci/unbind"
> in the /etc/rc.local can avoid shutdown hang but sometimes it also
> hang in the booting up process during the 200 times reboot test.
> 
> 4) I also found some messages in dmesg which show "ehci-pci
> 0000:00:1d.0: port 1 reset error -110."

It sounds like the BIOS is buggy.

> If there is any possibility to disable the EHCI controller in the
> Baytrail platform because the XHCI covers all the ports connected to
> EHCI controller.

You can disable the EHCI controller by setting "USB3.0 Configuration in 
Pre-OS" to enable, as you discovered.

>  And IIRC, there is only one host controller within
> EHCI and XHCI can be enabled in the Baytrail platform. I'm also trying
> to find out the kernel parameters to disable the EHCI driver, but
> currently there is no available one.

It's not a kernel parameter.  You can blacklist the ehci-pci and 
ehci-hcd modules in /etc/modprobe.d/local.conf.

Or you can turn off CONFIG_USB_EHCI_HCD in your .config and build a 
kernel with no EHCI support at all.

Alan Stern

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