From mboxrd@z Thu Jan  1 00:00:00 1970
From: linux@arm.linux.org.uk (Russell King - ARM Linux)
Date: Sat, 8 Dec 2012 00:08:50 +0000
Subject: [PATCH 1/2] thermal: Add support for thermal sensor for
 Kirkwood SoC
In-Reply-To: <20121207235904.GA15078@obsidianresearch.com>
References: <1354922151-3250-1-git-send-email-iwamatsu@nigauri.org>
 <20121207232459.GA4304@obsidianresearch.com>
 <20121207235904.GA15078@obsidianresearch.com>
Message-ID: <20121208000850.GZ14363@n2100.arm.linux.org.uk>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

On Fri, Dec 07, 2012 at 04:59:04PM -0700, Jason Gunthorpe wrote:
> On Fri, Dec 07, 2012 at 04:24:59PM -0700, Jason Gunthorpe wrote:
> > On Sat, Dec 08, 2012 at 08:15:50AM +0900, Nobuhiro Iwamatsu wrote:
> > > Some kirkwood SoC has thermal sensor.
> > > This patch adds support for 88F6282 and 88F6283.
> > 
> > Thanks! I was just about to write this.. Looks good here.
> 
> Ah, looking closer:
> 
> $ cat /sys/class/thermal/thermal_zone0/temp 
> 37
> 
> That should be 37000, the value out of the driver should be in
> milli-Celsius.
> 
> I'd use this equation instead:
> 
> 	*temp = ((322 - reg) * 10000 * 1000) / 13625;

Be careful of math overflows... make sure you do this calculation using
unsigned arithmetic as temperatures above 157 degress will cause this
to look like a negative number using signed math... However, that
probably won't ever be noticed because at 157 degrees, you'll definitely
be outside the operating limits of the device.