Re: [PATCH 2/2] arm: dt: Add device tree support for i2c instance 1 on exynos4 dt machine

["G, Manjunath Kondaiah" <manjugk@ti.com>]

On Tue, Jul 19, 2011 at 2:00 AM, Grant Likely <grant.likely@secretlab.ca> wrote:
> On Mon, Jul 18, 2011 at 5:53 AM, G, Manjunath Kondaiah
> <manjugk@linaro.org> wrote:
>> Abraham,
>> Few comments on i2c child devices handling:
>>
>> On 18 July 2011 06:20, Thomas Abraham <thomas.abraham@linaro.org> wrote:
>>> Add device node for i2c instance 1 and list all its connected slave
>>> devices.
>>>
>>> Signed-off-by: Thomas Abraham <thomas.abraham@linaro.org>
>>> ---
>>>  arch/arm/boot/dts/exynos4-smdkv310.dts  |   19 ++++++++++++++++++-
>>>  arch/arm/mach-exynos4/Kconfig           |    1 +
>>>  arch/arm/mach-exynos4/mach-exynos4-dt.c |    9 +++++++++
>>>  3 files changed, 28 insertions(+), 1 deletions(-)
>>>
>>> diff --git a/arch/arm/boot/dts/exynos4-smdkv310.dts b/arch/arm/boot/dts/exynos4-smdkv310.dts
>>> index d65c18c..29c40ed 100644
>>> --- a/arch/arm/boot/dts/exynos4-smdkv310.dts
>>> +++ b/arch/arm/boot/dts/exynos4-smdkv310.dts
>>> @@ -23,7 +23,7 @@
>>>        };
>>>
>>>        chosen {
>>> -               bootargs = "root=/dev/mmcblk0p1 rootfstype=ext3 rootwait console=ttySAC1,115200";
>>> +               bootargs = "root=/dev/mmcblk0p1 rootfstype=ext3 rootwait console=ttySAC1,115200 init=/linuxrc";
>>>        };
>>>
>>>        soc {
>>> @@ -64,5 +64,22 @@
>>>                        samsung,sdhci-cd-type = <0>;
>>>                        samsung,sdhci-clkdiv-external;
>>>                };
>>> +
>>> +               i2c@13870000 {
>>> +                       compatible = "samsung,s3c2440-i2c";
>>> +                       reg = <0x13870000 0x100>;
>>> +                       interrupts = <345>;
>>> +                       samsung,i2c-bus-number = <1>;
>>> +                       samsung,i2c-slave-addr = <16>;
>>> +                       samsung,i2c-sda-delay = <100>;
>>> +                       samsung,i2c-max-bus-freq = <100000>;
>>> +                       #address-cells = <1>;
>>> +                       #size-cells = <0>;
>>> +
>>> +                       wm8994@1a {
>>> +                               compatible = "wlf,wm8994";
>>> +                               reg = <0x1a>;
>>> +                       };
>>
>> The i2c child devices are board specific.
>> For ex: few boards such as smdkxxx based on exynos4 has wm8994 with
>> i2c1 controller
>> where as other boards based on exynos4 does not have any i2c1 devices.
>> Hence these child entries should go to board specific .dts file right?
>
> No, the i2c bus node should still appear in the SoC .dtsi file.  If a
> board doesn't use a particular i2c bus, then the board.dts file can
> add a status = "disabled"; property to the i2c bus node to disable it.

that's right. I am referring to I2C slave devices. For a given SoC,
two different
boards can have different i2c slave devices with different slave
address. In that case,
it is better to have i2c child/slave nodes in board .dts file.

-M