From mboxrd@z Thu Jan 1 00:00:00 1970 From: Russell King - ARM Linux Subject: Re: [PATCH 3/5] ARM: vexpress: Add DT support in v2m Date: Fri, 18 Nov 2011 17:52:03 +0000 Message-ID: <20111118175203.GI9581@n2100.arm.linux.org.uk> References: <1321036026-23411-1-git-send-email-pawel.moll@arm.com> <1321036026-23411-4-git-send-email-pawel.moll@arm.com> <20111117160536.GU9581@n2100.arm.linux.org.uk> <20111117183726.GE3044@localhost.localdomain> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: <20111117183726.GE3044-bi+AKbBUZKY6gyzm1THtWbp2dZbC/Bob@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: devicetree-discuss-bounces+gldd-devicetree-discuss=m.gmane.org-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org Sender: devicetree-discuss-bounces+gldd-devicetree-discuss=m.gmane.org-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org To: Dave Martin Cc: devicetree-discuss-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org, linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org, Pawel Moll List-Id: devicetree@vger.kernel.org On Thu, Nov 17, 2011 at 06:37:26PM +0000, Dave Martin wrote: > On Thu, Nov 17, 2011 at 04:05:37PM +0000, Russell King - ARM Linux wrote: > > You do understand that system_rev is for the system _revision_ not for > > some kind of system ID. For example, it's to identify whether we're on > > a revision 4, 5 or 6 system. > > > > However, with DT the differences in system revision should be encoded > > into the DT itself, and the kernel should not be making choices about > > the hardware off this. > > I can't comment on whether this is an abuse of system_rev, since I'm > not too familiar with that. > > I feel that Whether the value of the V2M_SYS_ID register should be put > in the DT is more doubtful though: the DT must describe the hardware > which cannot be probed. That is exactly my point - but we don't want V2M_SYS_ID controlling what hardware is there because then you'll end up having _drivers_ having to be aware of the system revision. Instead, the differences in device IP - when they're not discoverable from the device itself - should be encoded in DT to allow the device IP to be reused on different platforms which may not even have a V2M_SYS_ID register. That's what my objection is about: nothing should be using the overall system revision to determine anything about it.