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

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Message-ID: <51DE5EFF.5080005@ti.com>
Date:	Thu, 11 Jul 2013 10:30:07 +0300
From:	Roger Quadros <rogerq@...com>
To:	Alan Stern <stern@...land.harvard.edu>
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 07/10/2013 09:45 PM, Alan Stern wrote:
> 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.
> 
>> @@ -2248,7 +2253,21 @@ irqreturn_t usb_hcd_irq (int irq, void *__hcd)
>>  	 */
>>  	local_irq_save(flags);
>>  
>> -	if (unlikely(HCD_DEAD(hcd) || !HCD_HW_ACCESSIBLE(hcd)))
>> +	if (unlikely(HCD_DEAD(hcd)))
>> +		rc = IRQ_NONE;
>> +	else if (unlikely(!HCD_HW_ACCESSIBLE(hcd) && hcd->has_wakeup_irq)) {
>> +		/*
>> +		 * We got a wakeup interrupt while the controller was
>> +		 * suspending or suspended.  We can't handle it now, so
>> +		 * disable the IRQ and resume the root hub (and hence
>> +		 * the controller too).
>> +		 */
>> +		disable_irq_nosync(hcd->irq);
>> +		set_bit(HCD_FLAG_IRQ_DISABLED, &hcd->flags);
>> +		usb_hcd_resume_root_hub(hcd);
>> +
>> +		rc = IRQ_HANDLED;
>> +	} else if (unlikely(!HCD_HW_ACCESSIBLE(hcd)))
>>  		rc = IRQ_NONE;
> 
> In the interest of minimizing the amount of work needed in the most 
> common case, this should be written as:
> 
> 	else if (unlikely(!HCD_HW_ACCESSIBLE(hcd))) {
> 		if (hcd->has_wakeup_irq) {
> 			...
> 		} else
> 			rc = IRQ_NONE;
> 

OK.

>>  	else if (hcd->driver->irq(hcd) == IRQ_NONE)
>>  		rc = IRQ_NONE;
> 
> Apart from that, the patch is okay.  When you rearrange the logic, you 
> can add my Acked-by.
> 
Thanks.

cheers,
-roger
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