netdev - Re: [PATCH RFC] iwlwifi: add basic runtime PM support

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Message-ID: <4F0A3C62.6010403@intel.com>
Date:	Mon, 09 Jan 2012 09:01:22 +0800
From:	"Yan, Zheng" <zheng.z.yan@...el.com>
To:	Johannes Berg <johannes@...solutions.net>
CC:	wey-yi.w.guy@...el.com, ilw@...ux.intel.com,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	linux-wireless <linux-wireless@...r.kernel.org>
Subject: Re: [PATCH RFC] iwlwifi: add basic runtime PM support

On 01/06/2012 05:47 PM, Johannes Berg wrote:
> [add linux-wireless]
> 
> On Fri, 2012-01-06 at 10:41 +0800, Yan, Zheng wrote:
>> This simple patch adds open/close based runtime PM support to the iwlwifi driver.
>> Namely, make the driver suspend the device after shutting down the interface and
>> resume the device when activating the interface. In my test, suspending the device
>> can save about 0.4 watt power. The shortcoming is that the device no longer generate
>> rfkill changes interrupt.
> 
> NACK due to that last sentence. There's no way we can live with that in
> the general case -- and your patch isn't even configurable afaict. And
> I'm sure polling the rfkill flag would use just as much energy.
> 
It's configurable, runtime PM is disabled by default.

> There might be some value in this in a system that doesn't have a hard
> rfkill line, but that means this needs to be configurable since the
> device can't know whether there's a button or not [1].
> 
The patch targets system that only use software rfkill

Regards
Yan, Zheng


> johannes
> 
> [1] actually in theory it might be possible to determine whether or not
> the pin is floating or not? I doubt even that is possible with the HW we
> have though
> 

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