From mboxrd@z Thu Jan  1 00:00:00 1970
From: mikpe@it.uu.se (Mikael Pettersson)
Date: Mon, 28 Sep 2009 13:26:48 +0200
Subject: [PATCH 2/2] n2100: reduce power button timer to 1 Hz
In-Reply-To: <4AC0938A.1040009@nokia.com>
References: <19134.29011.460366.960746@pilspetsen.it.uu.se>
	<4AC06E8C.8090908@nokia.com>
	<19136.36934.791249.535941@pilspetsen.it.uu.se>
	<4AC0938A.1040009@nokia.com>
Message-ID: <19136.40312.174341.649031@pilspetsen.it.uu.se>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

Aaro Koskinen writes:
 > Hello,
 > 
 > Mikael Pettersson wrote:
 > > Aaro Koskinen writes:
 > >  > Mikael Pettersson wrote:
 > >  > > 10 Hz seems excessive, so this patch adds a compile-time option
 > >  > > to reduce the polling frequency to 1 Hz.
 > >  > > 
 > >  > > (This change could possibly be handled via a kernel boot option,
 > >  > > or even be made unconditional, but I opted for a compile-time
 > >  > > option for now.)
 > >  > 
 > >  > I don't think there is need to have an option for this. With HZ also
 > >  > round_jiffies() could be used, it doesn't need to be exact.
 > > 
 > > I don't quite follow you here. Can you elaborate?
 > 
 > round_jiffies() rounds the time up or down to a full second. It's useful for
 > timers that expire every N seconds. This way timeouts can be grouped, so there
 > is less wakeups.

Ah, the two sentences were not to be taken as a group:
1) no need for an option, i.e. reduce to 1 Hz unconditionally, and
2) with a 1 Hz timer, use round_jiffies() in the hope of grouping
   with other whole-Hz timers that also use round_jiffies().

I'll look into using round_jiffies().