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

[Stephen Warren]

On 02/07/2013 11:14 AM, Tom Warren wrote:
> Stephen,
> 
> On Thu, Feb 7, 2013 at 11:07 AM, Stephen Warren <swarren at wwwdotorg.org> wrote:
>> 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...
> 
> Thanks for the background info. I'm focusing on getting T114 I2C in
> right now, so I can move on to MMC and USB, and what I have seems
> reasonable/conforms to what's already done in U-Boot.

That doesn't necessarily make it correct.

> I don't want to get into reworking everyone's dts/dtsi files right now
> to move aliases around, or find out which boards really have unused
> I2C ports (Dalmore uses 'em all, BTW, according to our I2C
> spreadsheet). If you want to send a set of cleanup/re-org patches for
> everybody's DTS files, or even just the Tegra boards, feel free. I'll
> be glad to review it/apply it to u-boot-tegra later.

Sorry, but that's simply part of writing the .dts file for a board;
there is no way around that.