From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751098AbdAMQ4m (ORCPT ); Fri, 13 Jan 2017 11:56:42 -0500 Received: from mail.free-electrons.com ([62.4.15.54]:47080 "EHLO mail.free-electrons.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750721AbdAMQ4k (ORCPT ); Fri, 13 Jan 2017 11:56:40 -0500 Date: Fri, 13 Jan 2017 17:56:28 +0100 From: Boris Brezillon To: Marek Vasut Cc: Matthias Brugger , Guochun Mao , David Woodhouse , Brian Norris , Richard Weinberger , Cyrille Pitchen , Rob Herring , Mark Rutland , Russell King , linux-mtd@lists.infradead.org, devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-mediatek@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v1 2/2] arm: dts: mt2701: add nor flash node Message-ID: <20170113175628.1793f433@bbrezillon> In-Reply-To: <86c997be-f500-eaa1-3ba5-d21cff6223b7@gmail.com> References: <1484291609-20195-1-git-send-email-guochun.mao@mediatek.com> <1484291609-20195-3-git-send-email-guochun.mao@mediatek.com> <20170113151747.6bc85245@bbrezillon> <20170113172825.75d545a3@bbrezillon> <86c997be-f500-eaa1-3ba5-d21cff6223b7@gmail.com> X-Mailer: Claws Mail 3.13.2 (GTK+ 2.24.30; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 13 Jan 2017 17:44:12 +0100 Marek Vasut wrote: > On 01/13/2017 05:28 PM, Boris Brezillon wrote: > > On Fri, 13 Jan 2017 17:13:55 +0100 > > Marek Vasut wrote: > > > >> On 01/13/2017 04:12 PM, Matthias Brugger wrote: > >>> > >>> > >>> On 13/01/17 15:17, Boris Brezillon wrote: > >>>> On Fri, 13 Jan 2017 15:13:29 +0800 > >>>> Guochun Mao wrote: > >>>> > >>>>> Add Mediatek nor flash node. > >>>>> > >>>>> Signed-off-by: Guochun Mao > >>>>> --- > >>>>> arch/arm/boot/dts/mt2701-evb.dts | 25 +++++++++++++++++++++++++ > >>>>> arch/arm/boot/dts/mt2701.dtsi | 12 ++++++++++++ > >>>>> 2 files changed, 37 insertions(+) > >>>>> > >>>>> diff --git a/arch/arm/boot/dts/mt2701-evb.dts > >>>>> b/arch/arm/boot/dts/mt2701-evb.dts > >>>>> index 082ca88..85e5ae8 100644 > >>>>> --- a/arch/arm/boot/dts/mt2701-evb.dts > >>>>> +++ b/arch/arm/boot/dts/mt2701-evb.dts > >>>>> @@ -24,6 +24,31 @@ > >>>>> }; > >>>>> }; > >>>>> > >>>>> +&nor_flash { > >>>>> + pinctrl-names = "default"; > >>>>> + pinctrl-0 = <&nor_pins_default>; > >>>>> + status = "okay"; > >>>>> + flash@0 { > >>>>> + compatible = "jedec,spi-nor"; > >>>>> + reg = <0>; > >>>>> + }; > >>>>> +}; > >>>>> + > >>>>> +&pio { > >>>>> + nor_pins_default: nor { > >>>>> + pins1 { > >>>>> + pinmux = , > >>>>> + , > >>>>> + , > >>>>> + , > >>>>> + , > >>>>> + ; > >>>>> + drive-strength = ; > >>>>> + bias-pull-up; > >>>>> + }; > >>>>> + }; > >>>>> +}; > >>>>> + > >>>>> &uart0 { > >>>>> status = "okay"; > >>>>> }; > >>>>> diff --git a/arch/arm/boot/dts/mt2701.dtsi > >>>>> b/arch/arm/boot/dts/mt2701.dtsi > >>>>> index bdf8954..1eefce4 100644 > >>>>> --- a/arch/arm/boot/dts/mt2701.dtsi > >>>>> +++ b/arch/arm/boot/dts/mt2701.dtsi > >>>>> @@ -227,6 +227,18 @@ > >>>>> status = "disabled"; > >>>>> }; > >>>>> > >>>>> + nor_flash: spi@11014000 { > >>>>> + compatible = "mediatek,mt2701-nor", > >>>>> + "mediatek,mt8173-nor"; > >>>> > >>>> Why define both here? Is "mediatek,mt8173-nor" really providing a > >>>> subset of the features supported by "mediatek,mt2701-nor"? > >>>> > >>> > >>> I think even if the ip block is the same, we should provide both > >>> bindings, just in case in the future we find out that mt2701 has some > >>> hidden bug, feature or bug-feature. This way even if we update the > >>> driver, we stay compatible with older device tree blobs in the wild. > >>> > >>> We can drop the mt2701-nor in the bindings definition if you want. > > > > Oh, sorry, I misunderstood. What I meant is that if you want to > > list/support all possible compatibles, maybe you should just put one > > compatible in your DT and patch your driver (+ binding doc) to define > > all of them. > > Uh, what ? I lost you here :-) > > >> This exactly. We should have a DT compat in the form: > >> compatible = "vendor,-block", "vendor,-block"; > >> Then if we find a problem in the future, we can match on the > >> "vendor,-block" and still support the old DTs. > > > > Not sure it's only in term of whose IP appeared first. My understanding > > is that it's a way to provide inheritance. For example: > > > > ",", ","; > > > > or > > > > ",",","; > > > > BTW, which one is the oldest between mt8173 and mt2701? :-) > > And that's another thing and I agree with you, but I don't think that's > what we're discussing in this thread. But (!), OT, I think we should > codify the rules in Documentation/ . This discussion came up multiple > times recently. > > And my question still stands, what do we put into the DT here, IMO > compatible = "mediatek,mt2701-nor", "mediatek,mt8173-nor"; I'd say compatible = "mediatek,mt8173-nor"; because both compatible are referring to very specific IP version. It's not the same as compatible = "mediatek,mt8173-nor", "mediatek,mt81xx-nor"; where you clearly have a generic compatible which is overloaded by a specific one. But anyway, I'm not the one taking the decision here, let's wait for DT maintainers reviews. > and what goes into the binding document ? I guess both too ? If both exist, they should be both documented.