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

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Date:	Wed, 27 Aug 2014 01:17:36 +0800
From:	Gavin Guo <gavin.guo@...onical.com>
To:	Alan Stern <stern@...land.harvard.edu>
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

Hi Alan,

On Tue, Aug 26, 2014 at 11:38 PM, Alan Stern <stern@...land.harvard.edu> wrote:
> 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.

Thanks for your response, I'm sorry that I didn't describe the
question clearly. Because the EHCI support is built-in with Ubuntu
kernel. I tried to find a way to disable that. Unfortunately, I only
found "nousb" can disable it. But it will disable all the USB
subsystem. Don't know if there is any chance to disable EHCI only.

>
> Alan Stern
>
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