linux-kernel - Re: [PATCH] usb ehci_iaa

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Message-ID: <47F3CB91.1@rtr.ca>
Date:	Wed, 02 Apr 2008 14:08:17 -0400
From:	Mark Lord <lkml@....ca>
To:	Alan Stern <stern@...land.harvard.edu>
Cc:	David Brownell <david-b@...bell.net>, pavel@...e.cz,
	oliver@...kum.org, linux-usb@...r.kernel.org,
	linux-kernel@...r.kernel.org, jikos@...e.cz, gregkh@...e.de,
	akpm@...ux-foundation.org
Subject: Re: [PATCH] usb ehci_iaa_watchdog fix

Mark Lord wrote:
> Alan Stern wrote:
>> On Wed, 2 Apr 2008, Mark Lord wrote:
>>
>>> Yup, that does indeed cure it.
>>> Here's a patch, in case you didn't already generate one:
>>>
>>> Signed-off-by: Mark Lord <mlord@...ox.com>
>>>
>>> --- rc8/drivers/usb/host/ehci-hcd.c    2008-03-11 11:18:40.000000000 
>>> -0400
>>> +++ linux/drivers/usb/host/ehci-hcd.c    2008-04-02 
>>> 12:16:40.000000000 -0400
>>> @@ -289,9 +289,7 @@
>>>       * (a) SMP races against real IAA firing and retriggering, and
>>>       * (b) clean HC shutdown, when IAA watchdog was pending.
>>>       */
>>> -    if (ehci->reclaim
>>> -            && !timer_pending(&ehci->iaa_watchdog)
>>> -            && HC_IS_RUNNING(ehci_to_hcd(ehci)->state)) {
>>> +    if (ehci->reclaim && !timer_pending(&ehci->iaa_watchdog)) {
>>>          u32 cmd, status;
>>>  
>>>          /* If we get here, IAA is *REALLY* late.  It's barely
>>
>> Okay, I'm puzzled.  How could this make any difference?  
>> ehci_bus_suspend() calls end_unlink_async() anyway, whenever reclaim 
>> is set.
>>
>> Is the real problem that it does so before calling ehci_work() instead 
>> of after calling ehci_halt()?
>>
>> Mark, if you want to experiment some more, try reverting your patch 
>> above and moving:
> ..
> 
> Here's what I did, and yes, this also works.  Pick one.
> 
> This patch, suggested by Alan Stern, fixes the hung USB issues
> on my notebook from suspend/resume cycles.
> 
> Signed-off-by: Mark Lord <mlord@...ox.com>
> 
> --- rc8/drivers/usb/host/ehci-hub.c    2008-03-11 11:18:40.000000000 -0400
> +++ linux/drivers/usb/host/ehci-hub.c    2008-04-02 13:28:50.000000000 
> -0400
> @@ -135,8 +135,6 @@
>         hcd->state = HC_STATE_QUIESCING;
>     }
>     ehci->command = ehci_readl(ehci, &ehci->regs->command);
> -    if (ehci->reclaim)
> -        end_unlink_async(ehci);
>     ehci_work(ehci);
> 
>     /* Unlike other USB host controller types, EHCI doesn't have
> @@ -180,6 +178,9 @@
>     ehci_halt (ehci);
>     hcd->state = HC_STATE_SUSPENDED;
> 
> +    if (ehci->reclaim)
> +        end_unlink_async(ehci);
> +
>     /* allow remote wakeup */
>     mask = INTR_MASK;
>     if (!device_may_wakeup(&hcd->self.root_hub->dev))
..

Either patch is stable here, and have survived reboots and suspend/resumes,
with and without the 2.2Kohm resistor to drain residual USB voltage.

Which one should Andrew/Linus take?

-ml
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