linux-kernel - Re: [PATCH 1/1] mfd: omap-usb-host: Fix USB device detection problems on OMAP4 Panda

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Date:	Tue, 3 Dec 2013 11:43:18 +0200
From:	Roger Quadros <rogerq@...com>
To:	David Laight <David.Laight@...LAB.COM>, <lee.jones@...aro.org>,
	<sameo@...ux.intel.com>
CC:	<tomi.valkeinen@...com>, <balbi@...com>, <sr@...x.de>,
	<ljkenny.mailinglists@...il.com>, <linux-omap@...r.kernel.org>,
	<linux-usb@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/1] mfd: omap-usb-host: Fix USB device detection problems
 on OMAP4 Panda

On 12/02/2013 06:28 PM, David Laight wrote:
>> From: Roger Quadros [mailto:rogerq@...com]
>> On 11/29/2013 03:17 PM, David Laight wrote:
> ...
>>>> +	timeout = jiffies + msecs_to_jiffies(100);
>>>> +	while (!(usbhs_read(omap->uhh_base, OMAP_UHH_SYSSTATUS)
>>>> +			& OMAP_UHH_SYSSTATUS_RESETDONE)) {
>>>> +		cpu_relax();
>>
>> You mean use msleep(1) here instead of cpu_relax()?
>> Shouldn't be a problem IMO, but can you please tell me why that is better
>> as the reset seems to complete usually in the first iteration.
> 
> If it doesn't finish in the first iteration you don't want to
> spin the cpu for 100ms.
> 
> If it hasn't finished in the first millisecond, you probably expect
> it to actually time out - so you might as well look (say) every 10ms.
> 

Understood now. Thanks.

cheers,
-roger
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