From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751410AbdAPQJX (ORCPT ); Mon, 16 Jan 2017 11:09:23 -0500 Received: from mail-lf0-f66.google.com ([209.85.215.66]:34953 "EHLO mail-lf0-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750826AbdAPQJS (ORCPT ); Mon, 16 Jan 2017 11:09:18 -0500 Subject: Re: [PATCH v1 2/2] arm: dts: mt2701: add nor flash node To: Boris Brezillon , Rob Herring , Mark Rutland 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> <20170116094032.6f471f11@bbrezillon> 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 From: Marek Vasut Message-ID: Date: Mon, 16 Jan 2017 17:09:13 +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: <20170116094032.6f471f11@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 01/16/2017 09:40 AM, Boris Brezillon wrote: > 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 ;-). +1 :) > Rob, Mark, any opinion? > -- Best regards, Marek Vasut