[U-Boot] [PATCH v2 2/3] Tegra114: fdt: Update DT files with I2C info for T114/Dalmore

[Stephen Warren]

On 02/07/2013 09:17 AM, Tom Warren wrote:
> Laxman,
> 
> On Thu, Feb 7, 2013 at 7:57 AM, Laxman Dewangan <ldewangan at nvidia.com> wrote:
>> On Thursday 07 February 2013 04:56 AM, 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).
>>>
>>> Signed-off-by: Tom Warren <twarren at nvidia.com>
>>> ---
>>
>>
>>
>>> diff --git a/board/nvidia/dts/tegra114-dalmore.dts
>>> b/board/nvidia/dts/tegra114-dalmore.dts
>>> index 7315577..13b07f3 100644
>>> --- a/board/nvidia/dts/tegra114-dalmore.dts
>>> +++ b/board/nvidia/dts/tegra114-dalmore.dts
>>> @@ -6,8 +6,41 @@
>>>         model =NVIDIA Dalmore";
>>>         compatible =nvidia,dalmore", "nvidia,tegra114";
>>>
>>>   +     aliases {
>>> +               i2c0 =/i2c at 7000d000";
>>> +               i2c1 =/i2c at 7000c000";
>>> +               i2c2 =/i2c at 7000c400";
>>> +               i2c3 =/i2c at 7000c500";
>>> +               i2c4 =/i2c at 7000c700";
>>> +       };
>>
>>
>> Can we move this to tegar114.dtsi file.
> 
> I could, but why? Most, if not all, of the U-Boot boards that use DT
> are putting their aliases in the .dts file in the board directory.

Laxman, the issue here is that right now in U-Boot, I believe, if a
particular board only uses I2C adapters 0, 2, and 4, then only U-Boot
device IDs 0, 1, and 2 are defined, rather than IDs 0, 2, and 4. That's
why the aliases are in the per-board file for now, because the actual
set of I2C adapters enabled is board-specific.

Tom, as background for Laxman's request, for other devices (e.g. serial
ports), customer engineers have pushed back on that naming scheme, and
always want a specific HW device to end up with a static name,
irrespective of which other devices of the same type are used, if any.
For that reason, in the kernel, we have aliases for the serial ports in
tegra*.dtsi rather than in per-board files, and the names are static.

So I wonder if in U-Boot we really have to have IDs 0..n rather than
e.g. IDs 0, 2, 4 for the I2C ports (when some aren't used). Then, we
could just put the aliases in tegra*.dtsi, which makes life simpler when
creating board .dts files...