linux-kernel - Re: [PATCH v1 2/2] arm: dts: mt2701: add nor flash node

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Message-ID: <20170113162104.4d2a624c@bbrezillon>
Date:   Fri, 13 Jan 2017 16:21:04 +0100
From:   Boris Brezillon <boris.brezillon@...e-electrons.com>
To:     Matthias Brugger <matthias.bgg@...il.com>
Cc:     Guochun Mao <guochun.mao@...iatek.com>,
        David Woodhouse <dwmw2@...radead.org>,
        Brian Norris <computersforpeace@...il.com>,
        Marek Vasut <marek.vasut@...il.com>,
        Richard Weinberger <richard@....at>,
        Cyrille Pitchen <cyrille.pitchen@...el.com>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Russell King <linux@...linux.org.uk>,
        linux-mtd@...ts.infradead.org, devicetree@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 2/2] arm: dts: mt2701: add nor flash node

On Fri, 13 Jan 2017 16:12:20 +0100
Matthias Brugger <matthias.bgg@...il.com> wrote:

> On 13/01/17 15:17, Boris Brezillon wrote:
> > On Fri, 13 Jan 2017 15:13:29 +0800
> > Guochun Mao <guochun.mao@...iatek.com> wrote:
> >  
> >> Add Mediatek nor flash node.
> >>
> >> Signed-off-by: Guochun Mao <guochun.mao@...iatek.com>
> >> ---
> >>  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 = <MT2701_PIN_240_EXT_XCS__FUNC_EXT_XCS>,
> >> +				 <MT2701_PIN_241_EXT_SCK__FUNC_EXT_SCK>,
> >> +				 <MT2701_PIN_239_EXT_SDIO0__FUNC_EXT_SDIO0>,
> >> +				 <MT2701_PIN_238_EXT_SDIO1__FUNC_EXT_SDIO1>,
> >> +				 <MT2701_PIN_237_EXT_SDIO2__FUNC_EXT_SDIO2>,
> >> +				 <MT2701_PIN_236_EXT_SDIO3__FUNC_EXT_SDIO3>;
> >> +			drive-strength = <MTK_DRIVE_4mA>;
> >> +			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@...14000 {
> >> +		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.

I'm fine with this approach, but in this case, defining both is wrong.

> 
> We can drop the mt2701-nor in the bindings definition if you want.

Yes, please.

> 
> Regards,
> Matthias
> 
> >> +		reg = <0 0x11014000 0 0xe0>;
> >> +		clocks = <&pericfg CLK_PERI_FLASH>,
> >> +			 <&topckgen CLK_TOP_FLASH_SEL>;
> >> +		clock-names = "spi", "sf";
> >> +		#address-cells = <1>;
> >> +		#size-cells = <0>;
> >> +		status = "disabled";
> >> +	};
> >> +
> >>  	mmsys: syscon@...00000 {
> >>  		compatible = "mediatek,mt2701-mmsys", "syscon";
> >>  		reg = <0 0x14000000 0 0x1000>;  
> >