linux-kernel - Re: [PATCH 1/1] arm64: dts: imx8qxp-mek: add cm40

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Date: Fri, 5 Apr 2024 10:56:30 -0400
From: Frank Li <Frank.li@....com>
To: Francesco Dolcini <francesco@...cini.it>
Cc: Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
	Conor Dooley <conor+dt@...nel.org>, Shawn Guo <shawnguo@...nel.org>,
	Sascha Hauer <s.hauer@...gutronix.de>,
	Pengutronix Kernel Team <kernel@...gutronix.de>,
	Fabio Estevam <festevam@...il.com>,
	"open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" <devicetree@...r.kernel.org>,
	"open list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE" <imx@...ts.linux.dev>,
	"moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE" <linux-arm-kernel@...ts.infradead.org>,
	open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/1] arm64: dts: imx8qxp-mek: add cm40_i2c, wm8960/wm8962
 and sai[0,1,4,5]

On Fri, Apr 05, 2024 at 08:36:48AM +0200, Francesco Dolcini wrote:
> Hello Frank,
> 
> On Thu, Apr 04, 2024 at 12:19:13PM -0400, Frank Li wrote:
> > imx8qxp-mek use two kind audio codec, wm8960 and wm8962. Using dummy gpio
> > i2c bus mux to connect both i2c devices. One will probe failure and other
> > will probe success when devices driver check whoami. So one dtb can cover
> > both board configuration.
> > 
> > Signed-off-by: Frank Li <Frank.Li@....com>
> > ---
> >  arch/arm64/boot/dts/freescale/imx8qxp-mek.dts | 210 ++++++++++++++++++
> >  1 file changed, 210 insertions(+)
> > 
> > diff --git a/arch/arm64/boot/dts/freescale/imx8qxp-mek.dts b/arch/arm64/boot/dts/freescale/imx8qxp-mek.dts
> > index 8360bb851ac03..adff87c7cf305 100644
> > --- a/arch/arm64/boot/dts/freescale/imx8qxp-mek.dts
> > +++ b/arch/arm64/boot/dts/freescale/imx8qxp-mek.dts
> > @@ -44,6 +51,105 @@ usb3_data_ss: endpoint {
> 
> [...]
> 
> > +	/*
> > +	 * This dummy i2c mux. GPIO actually will not impact selection. At actual boards, only 1
> > +	 * device connectted. I2C client driver will check ID when probe. Only matched ID's driver
> > +	 * probe successfully.
> > +	 */
> > +	i2cvmux: i2cmux {
> > +		compatible = "i2c-mux-gpio";
> > +		#address-cells = <1>;
> > +		#size-cells = <0>;
> > +		mux-gpios = <&lsio_gpio5 0 GPIO_ACTIVE_HIGH>; /* use an unused gpio */
> 
> There is for sure people that have more experience and competency that
> me and it would be interesting to hear their feedback, but this
> looks like a bad hack, and you are just playing with the driver
> behavior to ensure that you get what you need.

We want to use one dtb to handle differecne bench boards because some chips
are out of life-cycle. I don't think it is 'hack' although not
straightforward.

check woiam is quite common at i2c drivers. All used method is quite
common, I just change it from difference point.

> 
> Francesco
> 
>