Re: [PATCH v3 2/2] arm64: dts: mt8173: Add I2C device node

[Eddie Huang]

Hi Dan,

On Fri, 2015-06-12 at 20:28 +0800, Daniel Kurtz wrote:
> On Fri, Jun 12, 2015 at 5:27 PM, Eddie Huang <eddie.huang@xxxxxxxxxxxx> 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".
> 
> 
> This is slightly misleading.  There are in fact 7 I2C controllers, but
> "i2c5" is dedicated for use by HDMI for ddc & hdcp.
> Is there a reason why the HDMI I2C port cannot be controlled by the
> generic i2c driver?
> 
We add some extra HW function to HDMI I2C port, we have special driver
to control this HW, not generic I2C driver. This is why I don't count
this hardware to generic I2C controllers. 

> Of course the hdmiddc / i2c5 node can always be added in a later
> patch, so this is no reason to hold up this patch.
> 
> > Signed-off-by: Eddie Huang <eddie.huang@xxxxxxxxxxxx>
> > ---
> >  arch/arm64/boot/dts/mediatek/mt8173-evb.dts | 50 ++++++++++++++++++++
> >  arch/arm64/boot/dts/mediatek/mt8173.dtsi    | 72 +++++++++++++++++++++++++++++
> >  2 files changed, 122 insertions(+)
> >
> > diff --git a/arch/arm64/boot/dts/mediatek/mt8173-evb.dts b/arch/arm64/boot/dts/mediatek/mt8173-evb.dts
> > index 43d5401..2e01988 100644
> > --- a/arch/arm64/boot/dts/mediatek/mt8173-evb.dts
> > +++ b/arch/arm64/boot/dts/mediatek/mt8173-evb.dts
> > @@ -33,6 +33,56 @@
> >         chosen { };
> >  };
> >
> > +&pio {
> 
> I don't think we needed to move these i2c pinmux descriptions from
> mt8173.dtsi to the board .dts file.
> 
> AFAICT, the "i2cN_pins_a" nodes defined here are the pinctl
> configuration that the corresponding enabled i2c nodes would choose.
> Thus, they are generic to the MT8173 SoC, not specific to any board.
> By themselves, these nodes do not actually select a pin configuration.
> 
> It is the nodes that *enable* the individual i2c nodes, and hence
> activate those pin settings, which is board specific.
> 
> Hence, if your intent is to have the evb enable all i2c nodes, it
> would have a set of nodes like this:
> 
> 
> &i2c0 {
>   pinctrl-names = "default";
>   pinctrl-0 = <&i2c0_pins_a>;
>   status = "okay";
> };
> 
> &i2c1 {
>  pinctrl-names = "default";
>  pinctrl-0 = <&i2c1_pins_a>;
>  status = "okay";
> };
> 
> ...
> 
I personally think put I2C pins in SoC dtsi is ok because it is basic
and fixed. Almost every platform need these pins, so not necessary to
care about dtb size. And these pins are fixed. We put pins that may
change by platforms to board dts, like mmc.

> 
> > +       i2c0_pins_a: i2c0@0 {
> 
> Do these nodes need the "@0"?
> 
Will remove.

> >
> > +               pins1 {
> > +                       pinmux = <MT8173_PIN_45_SDA0__FUNC_SDA0>,
> > +                                <MT8173_PIN_46_SCL0__FUNC_SCL0>;
> > +                       bias-disable;
> > +               };
> > +       };
> > +
> > +       i2c1_pins_a: i2c1@0 {
> > +               pins1 {
> > +                       pinmux = <MT8173_PIN_125_SDA1__FUNC_SDA1>,
> > +                                <MT8173_PIN_126_SCL1__FUNC_SCL1>;
> > +                       bias-disable;
> > +               };
> > +       };
> > +
> > +       i2c2_pins_a: i2c2@0 {
> > +               pins1 {
> > +                       pinmux = <MT8173_PIN_43_SDA2__FUNC_SDA2>,
> > +                                <MT8173_PIN_44_SCL2__FUNC_SCL2>;
> > +                       bias-disable;
> > +               };
> > +       };
> > +
> > +       i2c3_pins_a: i2c3@0 {
> > +               pins1 {
> > +                       pinmux = <MT8173_PIN_106_SDA3__FUNC_SDA3>,
> > +                                <MT8173_PIN_107_SCL3__FUNC_SCL3>;
> > +                       bias-disable;
> > +               };
> > +       };
> > +
> > +       i2c4_pins_a: i2c4@0 {
> > +               pins1 {
> > +                       pinmux = <MT8173_PIN_133_SDA4__FUNC_SDA4>,
> > +                                <MT8173_PIN_134_SCL4__FUNC_SCL4>;
> > +                       bias-disable;
> > +               };
> > +       };
> > +
> > +       i2c6_pins_a: i2c6@0 {
> > +               pins1 {
> > +                       pinmux = <MT8173_PIN_100_MSDC2_DAT0__FUNC_SDA5>,
> > +                                <MT8173_PIN_101_MSDC2_DAT1__FUNC_SCL5>;
> 
> These are the SDA/SCL pins for i2c port 6, so they should really be
> _SDA6 / _SCL6.
> However... I checked, and these settings are labeled "SDA5 & SCL5" in
> the datasheet.
> I recommend marking them correctly as 6 here and fixing the datasheet :-).
> 
We make mistake at the beginning not give these pins suitable name, if
we change now, it may affect already shipped products. So I tend to keep
it.

> >
> > +                       bias-disable;
> > +               };
> > +       };
> > +};
> > +
> >  &uart0 {
> >         status = "okay";
> >  };
> > diff --git a/arch/arm64/boot/dts/mediatek/mt8173.dtsi b/arch/arm64/boot/dts/mediatek/mt8173.dtsi
> > index b52ec43..6d3dbbdd 100644
> > --- a/arch/arm64/boot/dts/mediatek/mt8173.dtsi
> > +++ b/arch/arm64/boot/dts/mediatek/mt8173.dtsi
> > @@ -229,6 +229,78 @@
> >                         clocks = <&uart_clk>;
> >                         status = "disabled";
> >                 };
> > +
> > +               i2c0: i2c@11007000 {
> > +                       compatible = "mediatek,mt8173-i2c";
> > +                       reg = <0 0x11007000 0 0x70>,
> > +                             <0 0x11000100 0 0x80>;
> > +                       interrupts = <GIC_SPI 76 IRQ_TYPE_LEVEL_LOW>;
> > +                       clock-div = <16>;
> > +                       clocks = <&pericfg CLK_PERI_I2C0>,
> > +                                <&pericfg CLK_PERI_AP_DMA>;
> > +                       clock-names = "main", "dma";
> 
> The following fields must also be selected by the i2c nodes when they
> are enabled:
> 
> clock-frequency = <100000>;
> pinctrl-names = "default";
> pinctrl-0 = <&i2c0_pins_a>;
> #address-cells = <1>;
> #size-cells = <0>;
> 
> So, is there any reason not to also include them here in mt8173.dtsi
> so we can use them as defaults?
> This would simplify the i2c nodes in the board specific .dts files.
> The only field that might be board specific would be clock-frequency,
> but that is trivial to override on a port-by-port basis in board files
> as necessary.
> 
Since I tend to put I2C pins in SoC dtsi, I think I will put all you
mention above in SoC dtsi.

Eddie
Thanks


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