linux-kernel - Re: [PATCH v2 1/3] dt-bindings: Add I2C bindings for mt65xx/mt81xx.

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Date:	Thu, 13 Nov 2014 19:16:50 +0100
From:	Wolfram Sang <wsa@...-dreams.de>
To:	Xudong Chen <xudong.chen@...iatek.com>
Cc:	Mark Rutland <mark.rutland@....com>, arm@...nel.org,
	Matthias Brugger <matthias.bgg@...il.com>,
	srv_heupstream@...iatek.com, Sascha Hauer <kernel@...gutronix.de>,
	Rob Herring <robh+dt@...nel.org>,
	Pawel Moll <pawel.moll@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	Russell King <linux@....linux.org.uk>,
	Grant Likely <grant.likely@...aro.org>,
	Jean Delvare <jdelvare@...e.de>, Arnd Bergmann <arnd@...db.de>,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-i2c@...r.kernel.org,
	Yingjoe Chen <yingjoe.chen@...iatek.com>,
	Eddie Huang <eddie.huang@...iatek.com>,
	Nathan Chung <nathan.chung@...iatek.com>,
	YH Chen <yh.chen@...iatek.com>
Subject: Re: [PATCH v2 1/3] dt-bindings: Add I2C bindings for mt65xx/mt81xx.

On Tue, Nov 04, 2014 at 01:29:35PM +0800, Xudong Chen wrote:
> Add devicetree bindings for Mediatek Soc I2C driver.
> 
> Signed-off-by: Xudong Chen <xudong.chen@...iatek.com>
> ---
>  .../devicetree/bindings/i2c/i2c-mt6577.txt         | 39 ++++++++++++++++++++++
>  1 file changed, 39 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/i2c/i2c-mt6577.txt
> 
> diff --git a/Documentation/devicetree/bindings/i2c/i2c-mt6577.txt b/Documentation/devicetree/bindings/i2c/i2c-mt6577.txt
> new file mode 100644
> index 0000000..733e65e
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/i2c/i2c-mt6577.txt
> @@ -0,0 +1,39 @@
> +* Mediatek's I2C controller
> +
> +The Mediatek's I2C controller is used to interface with I2C devices.
> +
> +Required properties:
> +  - compatible: value should be either of the following.
> +      (a) "mediatek,mt6577-i2c", for i2c compatible with mt6577 i2c.
> +      (b) "mediatek,mt6589-i2c", for i2c compatible with mt6589 i2c.
> +      (c) "mediatek,mt8127-i2c", for i2c compatible with mt8127 i2c.
> +      (d) "mediatek,mt8135-i2c", for i2c compatible with mt8135 i2c.
> +  - reg: physical base address of the controller and dma base, length of memory mapped
> +    region.
> +  - interrupts: interrupt number to the cpu.
> +  - clock-div: the fixed value for frequency divider of clock source in i2c module.
> +    Each IC may be different.

? Doesn't that platform have CCF and can't we derive an I2C clock there?

> +  - clocks: clock name from clock manager
> +  - clock-names: clock name used in i2c driver probe

This needs names of the clocks. Check other binding documentation for
examples.

> +Optional properties:
> +  - clock-frequency: Frequency in Hz of the bus when transfer, the default value is 100000.
> +  - mediatek,have-pmic: platform can control i2c form special pmic side.
> +    Only mt6589 and mt8135 support this feature.
> +  - mediatek,have-dcm: platform has DCM(hardware digital clock manager) property.
> +  - mediatek,use-push-pull: IO use push-pull mode.

About the last 3 ones: Can't we encode this in the driver? Like, if the
compatible is "mediatek,mt6589-i2c" we know it has this and that but not
this?

> +
> +Example:
> +
> +	i2c0: i2c@...0d000 {
> +			compatible = "mediatek,mt6577-i2c";
> +			reg = <0x1100d000 0x70>,
> +			      <0x11000300 0x80>;
> +			interrupts = <GIC_SPI 44 IRQ_TYPE_LEVEL_LOW>;
> +			clock-frequency = <100000>;
> +			mediatek,have-pmic;
> +			clock-div = <16>;
> +			clocks = <&i2c0_ck>, <&ap_dma_ck>;
> +			clock-names = "main", "dma";
> +	};
> +
> -- 
> 1.8.1.1.dirty
> 

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