From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751054AbdAPIki (ORCPT ); Mon, 16 Jan 2017 03:40:38 -0500 Received: from mail.free-electrons.com ([62.4.15.54]:43503 "EHLO mail.free-electrons.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750855AbdAPIkf (ORCPT ); Mon, 16 Jan 2017 03:40:35 -0500 Date: Mon, 16 Jan 2017 09:40:32 +0100 From: Boris Brezillon To: Marek Vasut , Rob Herring , Mark Rutland Cc: Matthias Brugger , Guochun Mao , David Woodhouse , Brian Norris , Richard Weinberger , Cyrille Pitchen , 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: <20170116094032.6f471f11@bbrezillon> In-Reply-To: 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> <20170113175628.1793f433@bbrezillon> <0fafcd8d-cf99-de6b-728f-5e3637810b68@gmail.com> <20170114092958.022f2fc8@bbrezillon> 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 Sun, 15 Jan 2017 01:23:48 +0100 Marek Vasut wrote: > On 01/14/2017 09:29 AM, Boris Brezillon wrote: > > On Fri, 13 Jan 2017 18:33:40 +0100 > > Marek Vasut wrote: > > > >> On 01/13/2017 05:56 PM, Boris Brezillon wrote: > >>> 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 :-) > > > > I mean adding a new entry in the mtk_nor_of_ids table (in > > mtk-quadspi.c) so that the mediatek,mt2701-nor compatible string can be > > matched directly, and you won't need to define 2 compatible strings in > > your device tree. > > But then you grow the table in the driver, is that what we want if we > can avoid that ? The space you save by not growing the mtk_nor_of_ids table is lost in your dtbs, so I'm not sure the size argument is relevant here. Also, note that distros are shipping a lot of dtbs, and you're likely to have several boards based on the mt2701 SoC, so, for this specific use case, it's better to make the in-driver of-id table grow than specifying 2 compatibles in the DT. But as I said, I'm not sure we should rely on this argument to decide which approach to choose (we're talking about a few bytes 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 > >> > >> But then you don't have the ability to handle a block in this particular > >> SoC in case there's a bug found in it in the future, > >> so IMO it should be: > >> > >> compatible = "mediatek,mt2701-nor", "mediatek,mt8173-nor"; > > > > Sorry again, I meant > > > > compatible = "mediatek,mt2701-nor"; > > > >> > >>> compatible = "mediatek,mt8173-nor", "mediatek,mt81xx-nor"; > >> > >> This doesn't look right, since here we add two new compatibles ... > > > > That was just an example to describe how compatible inheritance works > > (at least that's my understanding of it), it does not apply to this > > particular use case. > > Well this is OK I guess, but then you can also use "mediatek,mt8173-nor" > as the oldest supported compatible and be done with it, no ? It looks a > bit crappy though, I admit that ... > Let's stop bikeshedding and wait for DT maintainers feedback before taking a decision ;-). Rob, Mark, any opinion?