Date: Wed, 9 Apr 2014 10:15:55 -0700
From: Guenter Roeck <linux@roeck-us.net>
To: Alexander Stein <alexander.stein@systec-electronic.com>
Cc: One Thousand Gnomes <gnomes@lxorguk.ukuu.org.uk>,
        David Cohen <david.a.cohen@linux.intel.com>, wim@iguana.be,
        tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com, x86@kernel.org,
        linux-kernel@vger.kernel.org, linux-watchdog@vger.kernel.org
Subject: Re: [PATCH 2/2] x86: intel-mid: add watchdog platform code for
 Merrifield
Message-ID: <20140409171555.GA30823@roeck-us.net>
References: <1396990744-10695-1-git-send-email-david.a.cohen@linux.intel.com>
 <2205089.MXSpGW1NLo@ws-stein>
 <20140409151822.GA21864@roeck-us.net>
 <3028945.75TnRQEiiW@ws-stein>
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On Wed, Apr 09, 2014 at 06:10:11PM +0200, Alexander Stein wrote:
> On Wednesday 09 April 2014 08:18:22, Guenter Roeck wrote:
> > On Wed, Apr 09, 2014 at 04:03:14PM +0200, Alexander Stein wrote:
> > > On Wednesday 09 April 2014 14:58:48, One Thousand Gnomes wrote:
> > > > > I'm getting curious: How can I use device-tree on x86(_64)?
> > > > > Reading the dependencies from CONFIG_OF it can only be used on 32bit systems with some special hardware bases.
> > > > > So, how to use otherwise?
> > > > 
> > > > There isn't any fundamental thing tying device tree to a given
> > > > architecture or 32bitness, it's just that sane PC architectures use ACPI
> > > > to enumerate devices, and/or have a discoverable bus architecture.
> > > > 
> > > > Some of the phones don't so this now becoems a point of consideration. In
> > > > fact it's already also used on CE4100 (which is an embedded media SoC
> > > > found in some TV devices and set-top boxes) and on the OLPC (One laptop
> > > > per child). There is no intrinsic reason it couldn't be used in other x86
> > > > special cases.
> > > > 
> > > > If its PC shaped however it probably has ACPI and ACPI and DT are not a
> > > > 1:1 mapping. ACPI has method invocations, and various firmware provided
> > > > interfaces such as the EC, Device tree is better at some other bits.
> > > 
> > > Yep, like SPI devices on embedded x86 hardware.
> > > 
> > > > Converting the phones to embedded device tree rather than adding a
> > > > billion little platform files on the other hand seems to me like a
> > > > no-brainer.
> > > 
> > > I found http://thread.gmane.org/gmane.linux.drivers.devicetree/4475. Why didn't that get into mainline?
> > > 
> > 
> > Isn't that patch set in mainline ?
> 
> Oh, I see that this patch didn't get included 1:1 as shown in that link. I only checked USE_OF in arch/x86/Kconfig which didn't get included that way :(
> 
> > We are working on a patch set to make DT support on x86 more
> > widely available. Thierry Reding did some work on it a while ago.
> > Some of it is upstream, other parts are available in 
> > 	https://github.com/avionic-design/linux/commits/medatom/master
> > 
> > We'll see if and what will be accepted upstream.
> 
> As far as I can see, CONFIG_OF is only selected if a specific hardware is enabled.
> 
Correct, and I expect that won't change. Default on x86 platform is ACPI.

Guenter
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