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

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Message-ID: <1326071127.13074.367.camel@wwguy-huron>
Date:	Sun, 08 Jan 2012 17:05:27 -0800
From:	"Guy, Wey-Yi" <wey-yi.w.guy@...el.com>
To:	"Yan, Zheng" <zheng.z.yan@...el.com>
Cc:	Johannes Berg <johannes@...solutions.net>, 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 Mon, 2012-01-09 at 09:55 +0800, Yan, Zheng wrote:
> On 01/09/2012 08:34 AM, Guy, Wey-Yi wrote:
> > On Mon, 2012-01-09 at 09:01 +0800, Yan, Zheng wrote:
> >> 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.
> > 
> > Somehow I miss it, how you configure it?
> > 
> change the value of /sys/devices/.../power/control to auto to enable the runtime PM.
> (e.g echo auto > /sys/devices/pci0000:00/0000:00:1c.3/0000:02:00.0/power/control)

I am not sure it is acceptable, how you expect user figure out the pci
space especially the NIC can be in any of the PCI slots.

> 
> >>
> >>> 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
> > 
> > How you control that?  
> I can't. Our team is working on runtime PM project, the purpose of the patch is
> more or less to demonstrate how much power can be saved.
> 
I understand, but unless we figure out either make rkill interrupt works
in runtime PM, or figure out the platform does not has HW RFKILL
automatically, I don't see how this patch can upstream without generate
a lot of issues and bug reports.

Thanks
Wey
> 


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