Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755188Ab3E2P1g (ORCPT ); Wed, 29 May 2013 11:27:36 -0400 Received: from avon.wwwdotorg.org ([70.85.31.133]:58200 "EHLO avon.wwwdotorg.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754476Ab3E2P1d (ORCPT ); Wed, 29 May 2013 11:27:33 -0400 Message-ID: <51A61E60.4070708@wwwdotorg.org> Date: Wed, 29 May 2013 09:27:28 -0600 From: Stephen Warren User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130106 Thunderbird/17.0.2 MIME-Version: 1.0 To: Benoit Cousson CC: "Mohammed, Afzal" , Jon Hunter , Russell King , "linux-doc@vger.kernel.org" , "devicetree-discuss@lists.ozlabs.org" , "linux-kernel@vger.kernel.org" , Rob Herring , Grant Likely , Benoit Cousson , "linux-omap@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" Subject: Re: [PATCH v2 11/14] Documentation: dt: binding: omap: am43x timer References: <223d90dc9eeab13d8496690d336cdf0f7d27cd22.1369658705.git.afzal@ti.com> <51A520B5.8040803@gmail.com> <51A52A16.1040204@wwwdotorg.org> <51A5BEB6.6070809@ti.com> In-Reply-To: <51A5BEB6.6070809@ti.com> X-Enigmail-Version: 1.4.6 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3256 Lines: 66 On 05/29/2013 02:39 AM, Benoit Cousson wrote: > Hi Afzal, > > On 05/29/2013 10:06 AM, Mohammed, Afzal wrote: >> Hi Jon, >> >> On Wed, May 29, 2013 at 03:35:10, Stephen Warren wrote: >>> On 05/28/2013 03:25 PM, Jon Hunter wrote: >> >>>>> ti,am335x-timer (applicable to AM335x devices) >>>>> ti,am335x-timer-1ms (applicable to AM335x devices) >>>>> + "ti,am4372-timer-1ms", "ti,am335x-timer-1ms" for AM43x 1ms timer >>>>> + "ti,am4372-timer", "ti,am335x-timer" for AM43x timers other than 1ms one >> >>>> If you are adding more compatibility strings, then this implies that the >>>> AM43x timers are not 100% compatible with any other device listed (such >>>> as am335x or any omap device). That's fine but you should state that in >>>> the changelog. If the AM43x timer registers are 100% compatible with >>>> existing devices you should not add these. >>> >>> I'm not sure that's true; .dts files should always include a compatible >>> value that describes the most specific model of the HW, plus any >>> baseline compatible value that the HW is compatible with. This allows >>> any required quirks/fixes/... to be applied for the specific HW model >>> later even if nobody knows right now they'll be needed. Hence, defining >>> new compatible values doesn't necessarily mean incompatible HW. >> >> Stephen took words out of my finger ;) >> >> Some explanations,I don;t >> >> 1. first compatible should be exact device [A], followed by compatible >> model (if one) >> 2. Minor effort in getting DT right the first time may help prevent >> difficult effort later modifying it (if a necessity comes), considering >> the fact that DT sources has to move out of Kernel at some point of >> time. And DT is not supposed to be modified, which may cause difficulty >> for the users (I had been a minor victim of this during rebase). >> >> As we both were in GPMC land earlier, an example, >> >> If my memory is right, GPMC IP in am335x is rev 6, and IP has 8 chip >> select, but one is not pinned out. Now assume that same IP is integrated >> in another SoC (probably OMAP4 has rev 6). Here if we use same compatible >> for both, driver cannot handle it properly (w/o knowledge about platform). >> But if exact compatible is mentioned, without modifying DT (which should >> be considered as a firmware) just by modifying Kernel, deciding based on >> compatible would help achieve what is required. > > That's true for the DTS itself, but here your are changing the binding > documentation which is supposed to reflect the driver "interface" in the > Device Tree model description. > > Since the driver does not support any new compatible string, you should > not update the binding. I don't agree here; the DT binding should define all the required and/or allowed values that must/should/can be present in the DT - the entire legal schema. The set of all compatible values is included in that, irrespective of whether a particular value actually (currently) defines a different HW interface or not. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/