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

[Tom Warren]

Stephen,

On Thu, Feb 7, 2013 at 11:20 AM, Stephen Warren <swarren at wwwdotorg.org> wrote:
> 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.

OK, how about this. For T114, I'll move the aliases to tegra114.dtsi,
and use 400KHz for all I2C nodes except I2C1 (saw some internal code
saying that it may not run well at that speed on the E1611 board).
Since all 5 controllers have devices behind them, I think it's OK to
leave all 5 in the aliases.

What do you think of that approach?

Adding Yen Lin to CC

Tom