linux-kernel - Re: [PATCH 01/10] clocksource: dw_apb_timer_of: use the clocksource as sched clock if necessary

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Date:	Tue, 4 Jun 2013 10:29:38 +0200
From:	Heiko Stübner <heiko@...ech.de>
To:	Linus Walleij <linus.walleij@...aro.org>
Cc:	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	John Stultz <john.stultz@...aro.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Mike Turquette <mturquette@...aro.org>,
	Seungwon Jeon <tgih.jun@...sung.com>,
	Jaehoon Chung <jh80.chung@...sung.com>,
	Chris Ball <cjb@...top.org>,
	"linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
	Grant Likely <grant.likely@...aro.org>,
	Rob Herring <rob.herring@...xeda.com>,
	"devicetree-discuss@...ts.ozlabs.org" 
	<devicetree-discuss@...ts.ozlabs.org>,
	Russell King <linux@....linux.org.uk>,
	Arnd Bergmann <arnd@...db.de>, Olof Johansson <olof@...om.net>
Subject: Re: [PATCH 01/10] clocksource: dw_apb_timer_of: use the clocksource as sched clock if necessary

Am Dienstag, 4. Juni 2013, 08:34:44 schrieb Linus Walleij:
> On Mon, Jun 3, 2013 at 12:56 AM, Heiko Stübner <heiko@...ech.de> wrote:
> > Currently the dw_apb_timer always expects a separate special timer to be
> > availbable for the sched_clock. Some devices using dw_apb_timers do not
> > have the sptimer but can use the clocksource as sched_clock.
> > Therefore this patch adds using the clocksource timer as
> > a fallback if no usable sched timer is found.
> > 
> > Signed-off-by: Heiko Stuebner <heiko@...ech.de>
> 
> Is this really what the patch does? I mean "ass the clocksourse as
> fallback", it seems more like that is controlled from the device tree,
> this looks more like some more careful handling of the device tree
> input making the sched_timer optional, it doesn't really "add"
> anything, does it?

Right, the commit message is probably based a bit to much on the before-state 
of the driver, always expecting the "sptimer" and panicing if not found.

How about:

Currently the dw_apb_timer always expects a separate special timer to be
availbable for the sched_clock. Some devices using dw_apb_timers do not
have this sptimer but can use the clocksource as sched_clock instead.

Therefore enable the driver to distiguish between devices with and without
sptimer based on the devicetree data and select the correct timer as
sched_clock.
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