linux-kernel - Re: [PATCH 6/8] ARM: dts: imx7d-sdb: Add GPIO expander node

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Date:   Sat, 15 Apr 2017 00:00:17 +0800
From:   Dong Aisheng <dongas86@...il.com>
To:     Shawn Guo <shawnguo@...nel.org>
Cc:     Andrey Smirnov <andrew.smirnov@...il.com>, yurovsky@...il.com,
        Sascha Hauer <kernel@...gutronix.de>,
        Fabio Estevam <fabio.estevam@....com>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Russell King <linux@...linux.org.uk>,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 6/8] ARM: dts: imx7d-sdb: Add GPIO expander node

On Fri, Apr 14, 2017 at 11:47:00AM +0800, Shawn Guo wrote:
> On Thu, Apr 13, 2017 at 06:32:40AM -0700, Andrey Smirnov wrote:
> > Add node for U38, a 74LV595PW serial-in shift register that acts as a
> > GPIO expander on the board.
> > 
> > Cc: yurovsky@...il.com
> > Cc: Sascha Hauer <kernel@...gutronix.de>
> > Cc: Fabio Estevam <fabio.estevam@....com>
> > Cc: Rob Herring <robh+dt@...nel.org>
> > Cc: Mark Rutland <mark.rutland@....com>
> > Cc: Russell King <linux@...linux.org.uk>
> > Cc: devicetree@...r.kernel.org
> > Cc: linux-kernel@...r.kernel.org
> > Cc: linux-arm-kernel@...ts.infradead.org
> > Signed-off-by: Andrey Smirnov <andrew.smirnov@...il.com>
> > ---
> >  arch/arm/boot/dts/imx7d-sdb.dts | 32 ++++++++++++++++++++++++++++++++
> >  1 file changed, 32 insertions(+)
> > 
> > diff --git a/arch/arm/boot/dts/imx7d-sdb.dts b/arch/arm/boot/dts/imx7d-sdb.dts
> > index 5be01a1..e0ff276 100644
> > --- a/arch/arm/boot/dts/imx7d-sdb.dts
> > +++ b/arch/arm/boot/dts/imx7d-sdb.dts
> > @@ -52,6 +52,30 @@
> >  		reg = <0x80000000 0x80000000>;
> >  	};
> >  
> > +	spi4 {
> > +		compatible = "spi-gpio";
> > +		pinctrl-names = "default";
> > +		pinctrl-0 = <&pinctrl_spi1>;
> > +		status = "okay";
> 
> The 'status' is not needed in this case.
> 
> > +		gpio-sck = <&gpio1 13 0>;
> > +		gpio-mosi = <&gpio1 9 0>;
> > +		cs-gpios = <&gpio1 12 0>;
> > +		num-chipselects = <1>;
> > +		#address-cells = <1>;
> > +		#size-cells = <0>;
> > +
> > +		gpio_spi: gpio_spi@0 {
> 
> gpio-expander might be a better node name?
> 
> > +			compatible = "fairchild,74hc595";
> > +			gpio-controller;
> > +			#gpio-cells = <2>;
> > +			reg = <0>;
> > +			registers-number = <1>;
> > +			 /* Enable PERI_3V3, SENSOR_RST_B and HDMI_RST*/
> > +			registers-default = /bits/ 8 <0x74>;
> 
> I do not see this property is documented or supported by kernel.

It's FSL internal invented property to do some trick on register
intialization and should be dropped.

Regards
Dong Aisheng