Re: [RFC PATCH 0/9] dt: dependencies (for deterministic driver initialization order based on the DT)

From: Alexander Holler <holler@ahsoftware.de>
To: Stephen Warren <swarren@wwwdotorg.org>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Grant Likely <grant.likely@linaro.org>
Cc: Mark Rutland <Mark.Rutland@arm.com>,
	"devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
	Jon Loeliger <jdl@jdl.com>, Russell King <linux@arm.linux.org.uk>,
	Arnd Bergmann <arnd@arndb.de>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Rob Herring <robh+dt@kernel.org>,
	Thierry Reding <thierry.reding@gmail.com>,
	"linux-arm-kernel@lists.infradead.org" 
	<linux-arm-kernel@lists.infradead.org>
Subject: Re: [RFC PATCH 0/9] dt: dependencies (for deterministic driver initialization order based on the DT)
Date: Wed, 27 Aug 2014 18:30:54 +0200	[thread overview]
Message-ID: <53FE07BE.7000809@ahsoftware.de> (raw)
In-Reply-To: <53FE05AE.9000406@wwwdotorg.org>

Am 27.08.2014 18:22, schrieb Stephen Warren:
> On 08/27/2014 08:44 AM, Catalin Marinas wrote:

>> It's not just optimisation but an important feature for new arm64 SoCs.
>> Given some Tegra discussions recently, in many cases the machine_desc
>> use on arm is primarily to initialise devices in the right order. If we
>> can solve this in a more deterministic way (other than deferred
>> probing), we avoid the need for a dedicated SoC platform driver (or
>> machine_desc) or workarounds like different initcall levels and explicit
>> DT parsing.
>
> A lot of the ordering is SW driver dependencies. I'm not sure how much
> of that can accurately be claimed as HW dependencies. As such, I'm not
> sure that putting dependencies into DT would be a good idea; it doesn't
> feel like HW data, and might well change if we restructure SW. It'd need
> some detailed research though.

Almost every phandle is a dependency, so the DT is already full with them.