linux-kernel - Re: [RFC PATCH 4/6] USB: ehci-omap: Suspend the controller during bus suspend

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Date:	Mon, 1 Jul 2013 11:33:52 +0300
From:	Roger Quadros <rogerq@...com>
To:	Alan Stern <stern@...land.harvard.edu>
CC:	<balbi@...com>, <tony@...mide.com>, <ruslan.bilovol@...com>,
	<linux-usb@...r.kernel.org>, <linux-omap@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [RFC PATCH 4/6] USB: ehci-omap: Suspend the controller during
 bus suspend

On 06/28/2013 10:18 PM, Alan Stern wrote:
> On Fri, 28 Jun 2013, Roger Quadros wrote:
> 
>> Just found the problem. It seems that enabling the ehci_irq _after_ the root hub is resumed
>> is the root cause of the problem. Doing so will miss events from the root hub.
> 
> This sounds like a bug in the IRQ setup.  It's the sort of thing you 
> see when a level-triggered IRQ is treated as though it were 
> edge-triggered.
> 
> In any case, the wakeup should have worked whether the IRQ was issued 
> or not.
> 
OK.
> 
> I appreciate the symmetry of putting the enable_irq call in ehci-hcd, 
> seeing as how the disable_irq is there too.  On the other hand, every 
> HCD using this mechanism is going to have to do the same thing, which 
> argues for putting the enable call in the core.  Perhaps at the start 

OK.

> of hcd_resume_work() instead of the end.
> 

We can't enable_irq at the start as the controller will only be resumed
after usb_remote_wakeup().

cheers,
-roger
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