From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750818AbdAOAXy (ORCPT ); Sat, 14 Jan 2017 19:23:54 -0500 Received: from mail-wm0-f67.google.com ([74.125.82.67]:36816 "EHLO mail-wm0-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750743AbdAOAXv (ORCPT ); Sat, 14 Jan 2017 19:23:51 -0500 Subject: Re: [PATCH v1 2/2] arm: dts: mt2701: add nor flash node To: Boris Brezillon 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> 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 From: Marek Vasut Message-ID: Date: Sun, 15 Jan 2017 01:23:48 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Icedove/45.4.0 MIME-Version: 1.0 In-Reply-To: <20170114092958.022f2fc8@bbrezillon> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 ? >>>> >>>>>> 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 ... -- Best regards, Marek Vasut