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

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Date:	Fri, 06 Jan 2012 10:47:49 +0100
From:	Johannes Berg <johannes@...solutions.net>
To:	"Yan, Zheng" <zheng.z.yan@...el.com>
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

[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.

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].

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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