From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from eggs.gnu.org ([2001:4830:134:3::10]:56939)
	by lists.gnu.org with esmtp (Exim 4.71)
	(envelope-from <B07421@freescale.com>) id 1V1kYT-0005ZN-Pj
	for qemu-devel@nongnu.org; Tue, 23 Jul 2013 17:55:40 -0400
Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71)
	(envelope-from <B07421@freescale.com>) id 1V1kYQ-0001hU-SM
	for qemu-devel@nongnu.org; Tue, 23 Jul 2013 17:55:37 -0400
Date: Tue, 23 Jul 2013 16:55:21 -0500
From: Scott Wood <scottwood@freescale.com>
References: <1374506897-41089-1-git-send-email-agraf@suse.de>
	<1374608328.15592.36@snotra>
	<7EA7921E-AF13-4485-94E5-B4068CEDAA9E@suse.de>
	<1374614344.15592.38@snotra>
	<EEFE6738-CF49-4C4A-BE17-D077804F5F16@suse.de>
In-Reply-To: <EEFE6738-CF49-4C4A-BE17-D077804F5F16@suse.de> (from
	agraf@suse.de on Tue Jul 23 16:44:02 2013)
Message-ID: <1374616521.15592.39@snotra>
MIME-Version: 1.0
Content-Type: text/plain; charset="us-ascii"; delsp=Yes; format=Flowed
Content-Disposition: inline
Content-Transfer-Encoding: quoted-printable
Subject: Re: [Qemu-devel] [PATCH] PPC: E500: Generate device tree on reset
List-Id: <qemu-devel.nongnu.org>
List-Unsubscribe: <https://lists.nongnu.org/mailman/options/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=unsubscribe>
List-Archive: <http://lists.nongnu.org/archive/html/qemu-devel>
List-Post: <mailto:qemu-devel@nongnu.org>
List-Help: <mailto:qemu-devel-request@nongnu.org?subject=help>
List-Subscribe: <https://lists.nongnu.org/mailman/listinfo/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=subscribe>
To: Alexander Graf <agraf@suse.de>
Cc: "qemu-ppc@nongnu.org list:PowerPC" <qemu-ppc@nongnu.org>, qemu-devel Developers <qemu-devel@nongnu.org>

On 07/23/2013 04:44:02 PM, Alexander Graf wrote:
>=20
>=20
> Am 23.07.2013 um 23:19 schrieb Scott Wood <scottwood@freescale.com>:
>=20
> > On 07/23/2013 04:15:59 PM, Alexander Graf wrote:
> >> On 23.07.2013, at 21:38, Scott Wood wrote:
> >> > On 07/22/2013 10:28:17 AM, Alexander Graf wrote:
> >> >> Today we generate the device tree once on machine =20
> initialization and then
> >> >> store the finalized blob in memory to reload it on reset.
> >> >> This is bad for 2 reasons. First we potentially waste a bunch =20
> of RAM for no
> >> >> good reason, as we have all information required to regenerate =20
> the device
> >> >> tree available anyways.
> >> >> The second reason is even more important. On machine init when =20
> we generate
> >> >> the device tree for the first time, we don't have all of the =20
> devices fully
> >> >> initialized yet. But the device tree needs to potentially walk =20
> devices to
> >> >> put information about them into the device tree.
> >> >
> >> > If you can't produce the entire device tree at init time, how =20
> can you calculate its size with a dry run?
> >> >
> >> > Device trees are generally pretty small; couldn't we just set a =20
> maximum size and allocate that much space?
> >> It's what we do, unless we load it from the disk. In that case we =20
> take the fdt size from disk.
> >
> > So why do we need the dry run stuff?
>=20
> Because dumpdtb otherwise generates a halfway complete dtb on the =20
> first dry pass as device realization is yet incomplete :).

What I mean is why have a first pass at all?

-Scott=