[U-Boot] [PATCH 1/2] Tegra114: fdt: Update DT files with I2C info for T114/Dalmore

[Stephen Warren <swarren@wwwdotorg.org>]

On 01/29/2013 01:40 PM, Tom Warren wrote:
> Stephen,
> 
> On Tue, Jan 29, 2013 at 1:09 PM, Stephen Warren <swarren@wwwdotorg.org> wrote:
>> On 01/29/2013 12:19 PM, Tom Warren wrote:
>>> Note that T114 does not have a separate/different DVC (power I2C)
>>> controller like T20 - all 5 I2C controllers are identical, but
>>> I2C5 is used to designate the controller intended for power
>>> control (PWR_I2C in the schematics).

>> If you do keep this node, it needs the clocks property filled in.
>>
>>> +     i2c at 7000c000 {
>>> +             compatible = "nvidia,tegra114-i2c", "nvidia,tegra20-i2c";
>>
>> The I2C nodes also aren't backwards-compatible.
> 
> They were on T30 (same compatible string there, except of course
> s/114/30/). And the tegra20-i2c is needed for fdtdec.c to find it
> (compat_names table).

Yes, I believe the HW changes between Tegra20 and Tegra30 were such that
the Tegra20 driver would run unmodified on Tegra30 without issue. I
don't believe that's the case for Tegra114 though. The solution would be
to add the Tegra114 compatible value to the I2C driver so that it can
search for both.

>>> +             reg = <0x7000c000 0x100>;
>>
>> The interrupts property is missing here.
> 
> I didn't have an interrupts property for I2C on the T30 dts files,
> either.

That sounds like a bug in the DT.

> What is it used for in U-Boot?

U-Boot doesn't use interrupts at least on Tegra, so it's not used.
However, it'd be best to keep the U-Boot DT in line with the kernel DT
so we can easily spot differences. There has been talk of trying to use
the same DT for both too, although we're a long long way off from that.

> If it's really needed, can I
> just crib it from the kernel dts file(s)?

Yes, but the Tegra114 patches aren't all checked in yet. See the
following proposed patch for what you need:

https://lkml.org/lkml/2013/1/29/235

(note that patch is missing the clocks properties since the clock
binding isn't finalized and checked in yet)

>>> diff --git a/board/nvidia/dts/tegra114-dalmore.dts b/board/nvidia/dts/tegra114-dalmore.dts
>>
>> Board changes would usually be a separate patch to an SoC change, but I
>> guess not a big deal.
> 
> Actually, this is the way I've always done DT files (in a separate
> patch), and then the config files in a separate patch the enable the
> feature.

I meant that tegra114.dtsi and tegra114-dalmore.dts would usually be
separate patches.

>> All 5 I2C ports are used on the board and only support 100KHz? That
>> seems unusual, but I suppose it's possible.
> 
> That's the way I have it on T30, and looking at
> arch/arm/boot/dts/tegra30.dtsi in the kernel, all 5 ports are set to
> 100KHz.

But this is board-specific; it depends on which of the I2C controllers
are actually pinmux'd out onto the board (-> which to enable), and which
devices are attached to those buses (-> max I2C clock rate). I don't see
how Tegra30 nor tegra30.dtsi are relevant here.