linux-kernel - RE: [EXT] Re: [PATCH 1/3] dt-bindings: i2c: add optional mul-value property to binding

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Message-ID: <AM0PR04MB43537B281229FA847CE6F2B897320@AM0PR04MB4353.eurprd04.prod.outlook.com>
Date:   Wed, 8 May 2019 11:44:50 +0000
From:   Chuanhua Han <chuanhua.han@....com>
To:     Rob Herring <robh@...nel.org>
CC:     "mark.rutland@....com" <mark.rutland@....com>,
        "shawnguo@...nel.org" <shawnguo@...nel.org>,
        "s.hauer@...gutronix.de" <s.hauer@...gutronix.de>,
        Leo Li <leoyang.li@....com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-i2c@...r.kernel.org" <linux-i2c@...r.kernel.org>,
        "kernel@...gutronix.de" <kernel@...gutronix.de>,
        dl-linux-imx <linux-imx@....com>,
        "festevam@...il.com" <festevam@...il.com>,
        "wsa+renesas@...g-engineering.com" <wsa+renesas@...g-engineering.com>,
        "u.kleine-koenig@...gutronix.de" <u.kleine-koenig@...gutronix.de>,
        "eha@...f.com" <eha@...f.com>,
        "linux@...pel-privat.de" <linux@...pel-privat.de>,
        Sumit Batra <sumit.batra@....com>,
        "l.stach@...gutronix.de" <l.stach@...gutronix.de>,
        "peda@...ntia.se" <peda@...ntia.se>
Subject: RE: [EXT] Re: [PATCH 1/3] dt-bindings: i2c: add optional mul-value
 property to binding



> -----Original Message-----
> From: Rob Herring <robh@...nel.org>
> Sent: 2019年5月3日 4:59
> To: Chuanhua Han <chuanhua.han@....com>
> Cc: mark.rutland@....com; shawnguo@...nel.org; s.hauer@...gutronix.de;
> Leo Li <leoyang.li@....com>; linux-kernel@...r.kernel.org;
> devicetree@...r.kernel.org; linux-arm-kernel@...ts.infradead.org;
> linux-i2c@...r.kernel.org; kernel@...gutronix.de; dl-linux-imx
> <linux-imx@....com>; festevam@...il.com;
> wsa+renesas@...g-engineering.com; u.kleine-koenig@...gutronix.de;
> eha@...f.com; linux@...pel-privat.de; Sumit Batra <sumit.batra@....com>;
> l.stach@...gutronix.de; peda@...ntia.se
> Subject: [EXT] Re: [PATCH 1/3] dt-bindings: i2c: add optional mul-value
> property to binding
> 
> Caution: EXT Email
> 
> On Tue, Apr 30, 2019 at 12:32:40PM +0800, Chuanhua Han wrote:
> > NXP Layerscape SoC have up to three MUL options available for all
> > divider values, we choice of MUL determines the internal monitor rate
> > of the I2C bus (SCL and SDA signals):
> > A lower MUL value results in a higher sampling rate of the I2C signals.
> > A higher MUL value results in a lower sampling rate of the I2C signals.
> >
> > So in Optional properties we added our custom mul-value property in
> > the binding to select which mul option for the device tree i2c
> > controller node.
> >
> > Signed-off-by: Chuanhua Han <chuanhua.han@....com>
> > ---
> >  Documentation/devicetree/bindings/i2c/i2c-imx.txt | 3 +++
> >  1 file changed, 3 insertions(+)
> >
> > diff --git a/Documentation/devicetree/bindings/i2c/i2c-imx.txt
> > b/Documentation/devicetree/bindings/i2c/i2c-imx.txt
> > index b967544590e8..ba8e7b7b3fa8 100644
> > --- a/Documentation/devicetree/bindings/i2c/i2c-imx.txt
> > +++ b/Documentation/devicetree/bindings/i2c/i2c-imx.txt
> > @@ -18,6 +18,9 @@ Optional properties:
> >  - sda-gpios: specify the gpio related to SDA pin
> >  - pinctrl: add extra pinctrl to configure i2c pins to gpio function for i2c
> >    bus recovery, call it "gpio" state
> > +- mul-value: NXP Layerscape SoC have up to three MUL options
> > +available for all I2C divider values, it describes which MUL we
> > +choose to use for the driver, the values should be 1,2,4.
> 
> Needs a vendor prefix. I don't find 'value' to add anything nor do I understand
> what MUL is.
Yes,you are right!
> 
> If it is determined by SoC rather than board, then it should perhaps be implied
> by compatible.
This is determined by the SOC, but it has three options to choose from, 
so I think it's better to use the optional option instead of compatible

> 
> Rob