linux-kernel - Re: Missing USB XHCI and EHCI reset for kexec

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Date:	Tue, 15 Apr 2014 12:04:17 +0200
From:	stefani@...bold.net
To:	Thadeu Lima de Souza Cascardo <cascardo@...ux.vnet.ibm.com>
Cc:	Benjamin Herrenschmidt <benh@....ibm.com>,
	linux-usb <linux-usb@...r.kernel.org>,
	linux-kernel@...r.kernel.org, Greg KH <greg@...ah.com>,
	Alan Stern <stern@...land.harvard.edu>,
	sarah.a.sharp@...ux.intel.com
Subject: Re: Missing USB XHCI and EHCI reset for kexec


Zitat von Thadeu Lima de Souza Cascardo <cascardo@...ux.vnet.ibm.com>:

> On Mon, Apr 14, 2014 at 05:44:58PM +0200, stefani@...bold.net wrote:
>>
>> Zitat von Benjamin Herrenschmidt <benh@....ibm.com>:
>>
>> >I don't know about EHCI specifically but this is a known issue with
>> >XHCI, I observe similar issues on other powerpc platforms (servers)
>> >and this isn't architecture specific (looks more like actualy xhc
>> >implementation specific).
>> >
>> >Thadeu Cascardo (on CC) has been the one investigating that on our side,
>> >he might have more to add including patches.
>> >
>>
>> I have now a kernel 3.14 dmesg log of the problem. After a kexec the
>> kexeced 3.14 kernel shows:
>>
>> [    1.170029] xhci_hcd 0001:03:00.0: xHCI Host Controller
>> [    1.175306] xhci_hcd 0001:03:00.0: new USB bus registered,
>> assigned bus number 1
>> [    1.212561] xhci_hcd 0001:03:00.0: Host not halted after 16000
>> microseconds.
>> [    1.219621] xhci_hcd 0001:03:00.0: can't setup: -110
>> [    1.224597] xhci_hcd 0001:03:00.0: USB bus 1 deregistered
>> [    1.230021] xhci_hcd 0001:03:00.0: init 0001:03:00.0 fail, -110
>> [    1.235955] xhci_hcd: probe of 0001:03:00.0 failed with error -110
>>
>
> What is your controller vendor and device IDs? Is that a TI chip?
>

Yes it is a TI chip, vendor ID 104c and product ID 8241.

> Can you check if the patch I sent a month ago fixes it? [1] There's the
> whole story there. In fact, you will also need something like the patch
> below. Can you apply only the first one, verify, and, then, the other
> one as well, and report what worked for you?
>
> [1] http://marc.info/?l=linux-usb&m=139483181809062&w=2
>

I tried the attach patch and it did not help. This is what i expected  
because this is a fix in the shutdown path, which will never called  
when doing a forced kexec.

I have a running a 3.10.23 kernel. This kernel do a kexec for a kernel  
3.14. Since the kernel 3.10.23 did not performe a clean shutdown, the  
state of the XHCI Controller is undefined. So when kernel 3.14 will  
probe XHCI it will find a XHCI controller which was not performed a  
reset.

So i think it is necessary to reset the XHCI controller and all  
devices on this bus. This is what i do with a "echo 1  
 >/sys/bus/pci/drivers/xhci_hcd/0001:03:00.0/reset" before the kexec.

- Stefani


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