linux-kernel - Re: [PATCH 5/6] USB: Support wakeup IRQ for suspended controllers

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Date:	Wed, 10 Jul 2013 15:08:43 -0400 (EDT)
From:	Alan Stern <stern@...land.harvard.edu>
To:	Roger Quadros <rogerq@...com>
cc:	gregkh@...uxfoundation.org, <balbi@...com>,
	<sergei.shtylyov@...entembedded.com>, <khilman@...aro.org>,
	<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: [PATCH 5/6] USB: Support wakeup IRQ for suspended controllers

On Wed, 10 Jul 2013, Roger Quadros wrote:

> Some platforms e.g. ehci-omap can generate an interrupt
> (i.e. remote wakeup) even when the controller is suspended i.e.
> HW_ACCESSIBLE is cleared.
> 
> Introduce a flag "has_wakeup_irq" in struct usb_hcd to indicate
> such cases.
> 
> We tackle this case by disabling the IRQ, scheduling a
> hub resume and enabling back the IRQ after the controller has
> resumed. This ensures that the IRQ handler runs only after the
> controller is accessible.

Oh yes, one more thing...

> @@ -132,6 +134,7 @@ struct usb_hcd {
>  	unsigned		wireless:1;	/* Wireless USB HCD */
>  	unsigned		authorized_default:1;
>  	unsigned		has_tt:1;	/* Integrated TT in root hub */
> +	unsigned		has_wakeup_irq:1; /* Can IRQ when suspended */

Please add a highly visible comment here, warning that has_wakeup_irq
should never be set on systems with shared IRQs.  Having both would ...
well, it would indicate a really bad system design.

Alan Stern

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