From mboxrd@z Thu Jan 1 00:00:00 1970 From: Marek Vasut Subject: Re: [PATCH v1 2/2] arm: dts: mt2701: add nor flash node Date: Fri, 13 Jan 2017 18:33:40 +0100 Message-ID: <0fafcd8d-cf99-de6b-728f-5e3637810b68@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> <20170113175628.1793f433@bbrezillon> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20170113175628.1793f433@bbrezillon> Sender: devicetree-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Boris Brezillon Cc: Matthias Brugger , Guochun Mao , David Woodhouse , Brian Norris , Richard Weinberger , Cyrille Pitchen , Rob Herring , Mark Rutland , Russell King , linux-mtd-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org, devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org, linux-mediatek-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: devicetree@vger.kernel.org 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 :-) >> >>>> 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"; > compatible = "mediatek,mt8173-nor", "mediatek,mt81xx-nor"; This doesn't look right, since here we add two new compatibles ... > 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. > -- Best regards, Marek Vasut -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html