linux-kernel - Re: [PATCH v4 2/2] arm64: dts: mt8173: Add I2C device node

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Date:	Mon, 22 Jun 2015 11:36:10 +0800
From:	Eddie Huang <eddie.huang@...iatek.com>
To:	Daniel Kurtz <djkurtz@...omium.org>
CC:	Matthias Brugger <matthias.bgg@...il.com>,
	Sascha Hauer <s.hauer@...gutronix.de>,
	"open list:OPEN FIRMWARE AND..." <devicetree@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	<linux-mediatek@...ts.infradead.org>
Subject: Re: [PATCH v4 2/2] arm64: dts: mt8173: Add I2C device node

Hi Dan,

On Thu, 2015-06-18 at 23:16 +0800, Daniel Kurtz wrote:
> On Wed, Jun 17, 2015 at 11:08 PM, Eddie Huang <eddie.huang@...iatek.com> wrote:
> > Add MT8173 I2C device nodes, include I2C controllers and pins.
> > MT8173 has six I2C controllers, from i2c0 to i2c6, exclude i2c5.
> > The 6th I2C controller register base doesn't next to 5th I2C,
> > and there is a hardware between 5th and 6th I2C controller. So
> > SoC designer name 6th controller as "i2c6", not "i2c5".
> >
> > Signed-off-by: Eddie Huang <eddie.huang@...iatek.com>
> > ---
> >  arch/arm64/boot/dts/mediatek/mt8173.dtsi | 144 +++++++++++++++++++++++++++++++
> >  1 file changed, 144 insertions(+)
> >
> > diff --git a/arch/arm64/boot/dts/mediatek/mt8173.dtsi b/arch/arm64/boot/dts/mediatek/mt8173.dtsi
> > index b52ec43..1816c8f 100644
> > --- a/arch/arm64/boot/dts/mediatek/mt8173.dtsi
> > +++ b/arch/arm64/boot/dts/mediatek/mt8173.dtsi
> > @@ -158,6 +158,54 @@
> >                         interrupts = <GIC_SPI 145 IRQ_TYPE_LEVEL_HIGH>,
> >                                                 <GIC_SPI 146 IRQ_TYPE_LEVEL_HIGH>,
> >                                                 <GIC_SPI 147 IRQ_TYPE_LEVEL_HIGH>;
> > +
> > +                       i2c0_pins_a: i2c0 {
> > +                               pins1 {
> > +                                       pinmux = <MT8173_PIN_45_SDA0__FUNC_SDA0>,
> > +                                                <MT8173_PIN_46_SCL0__FUNC_SCL0>;
> > +                                       bias-disable;
> > +                               };
> > +                       };
> > +
> > +                       i2c1_pins_a: i2c1 {
> > +                               pins1 {
> > +                                       pinmux = <MT8173_PIN_125_SDA1__FUNC_SDA1>,
> > +                                                <MT8173_PIN_126_SCL1__FUNC_SCL1>;
> > +                                       bias-disable;
> > +                               };
> > +                       };
> > +
> > +                       i2c2_pins_a: i2c2 {
> > +                               pins1 {
> > +                                       pinmux = <MT8173_PIN_43_SDA2__FUNC_SDA2>,
> > +                                                <MT8173_PIN_44_SCL2__FUNC_SCL2>;
> > +                                       bias-disable;
> > +                               };
> > +                       };
> > +
> > +                       i2c3_pins_a: i2c3 {
> > +                               pins1 {
> > +                                       pinmux = <MT8173_PIN_106_SDA3__FUNC_SDA3>,
> > +                                                <MT8173_PIN_107_SCL3__FUNC_SCL3>;
> > +                                       bias-disable;
> > +                               };
> > +                       };
> > +
> > +                       i2c4_pins_a: i2c4 {
> > +                               pins1 {
> > +                                       pinmux = <MT8173_PIN_133_SDA4__FUNC_SDA4>,
> > +                                                <MT8173_PIN_134_SCL4__FUNC_SCL4>;
> > +                                       bias-disable;
> > +                               };
> > +                       };
> > +
> > +                       i2c6_pins_a: i2c6 {
> > +                               pins1 {
> > +                                       pinmux = <MT8173_PIN_100_MSDC2_DAT0__FUNC_SDA5>,
> > +                                                <MT8173_PIN_101_MSDC2_DAT1__FUNC_SCL5>;
> > +                                       bias-disable;
> > +                               };
> > +                       };
> >                 };
> >
> >                 watchdog: watchdog@...07000 {
> > @@ -229,6 +277,102 @@
> >                         clocks = <&uart_clk>;
> >                         status = "disabled";
> >                 };
> > +
> > +               i2c0: i2c@...07000 {
> > +                       compatible = "mediatek,mt8173-i2c";
> > +                       reg = <0 0x11007000 0 0x70>,
> > +                             <0 0x11000100 0 0x80>;
> > +                       interrupts = <GIC_SPI 76 IRQ_TYPE_LEVEL_LOW>;
> > +                       clock-div = <16>;
> 
> According to the i2c-mt6577 dt binding:
>    - clock-div: the fixed value for frequency divider of clock source in i2c
>      module. Each IC may be different.
> 
> For other drivers I've seen this kind of hardware-specific value
> implemented as a table in the driver that is indexed based on the
> compatible.
> 
> Any particular reason to specify it here in every device tree node instead?
> 

If put in device tree, it is not necessary to add new compatible if new
SoC has the same I2C controller hardware except clock-div.The benefit is
keep driver clean, but the side-effect is add clock-div in device node.I
assume clock-div has the same concept of clock, so I put in device tree.

Eddie
Thanks


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