[PATCH 2/2] ARM: dts: socfpga: Add a 3.3V fixed regulator node

[Doug Anderson]

Hi,

On Fri, Oct 17, 2014 at 12:19 PM, Dinh Nguyen
<dinguyen at opensource.altera.com> wrote:
> On 10/17/2014 11:57 AM, Doug Anderson wrote:
>> Dinh,
>>
>> On Thu, Oct 16, 2014 at 2:03 PM,  <dinguyen at opensource.altera.com> wrote:
>>> From: Dinh Nguyen <dinguyen at opensource.altera.com>
>>>
>>> Without the 3.3V regulator node, the SDMMC driver will give these warnings:
>>>
>>> dw_mmc ff704000.dwmmc0: No vmmc regulator found
>>> dw_mmc ff704000.dwmmc0: No vqmmc regulator found
>>>
>>> This patch adds the regulator node, and points the SD/MMC to the regulator.
>>>
> [...]
>>>
>>> -               dwmmc0 at ff704000 {
>>> +               mmc0: dwmmc0 at ff704000 {
>>>                         num-slots = <1>;
>>>                         broken-cd;
>>>                         bus-width = <4>;
>>> @@ -41,4 +41,13 @@
>>>                         cpu1-start-addr = <0xffd080c4>;
>>>                 };
>>>         };
>>> +
>>> +       regulator_3_3v_hps: fixed_3_3v_hps_regulator at 0 {
>>
>> nit: no @0 since there is no "reg" (register) under this node.
>>
>> nit: usually people don't like "_" in node names.  ...I would probably
>> do this but I'm not an expert:
>>   regulator_3_3v_hps: hps-regulator {
>
> Ok..will fix up.
>
>>
>> This regulator also looks pretty bogus to me.  Is this really a
>> regulator that software has no control over?  It means you can't fully
>> reset a card but I guess that's OK.
>
> Yes, this is a generic 3.3V regulator that is used for the 3.3V power
> rail for the SOC, and any IP the needs 3.3V.
>
> Schematics are here:
> http://www.rocketboards.org/pub/Documentation/AlteraSoCDevelopmentBoard/c5_soc_devkit_c.pdf?t=1365712679
>
> http://www.rocketboards.org/pub/Documentation/ArrowSoCKitEvaluationBoard/SoCKit_RevC.pdf
>
> And right, I don't see anyway to be able to reset the card.
>
>>
>> I'd also expect this regulator to be defined in the same dts / dtsi
>> file that it's used in.  Your current patch says "there's a generic
>> 3.3V regulator on all boards of the socfpga_arria5 class even if they
>> don't use MMC, but the "socfpga_arria5_socdk" uses it for MMC.  Is
>> that really true?
>>
>
> yeah...My original patch had the regulator placed in it's appropriate
> dts board file, but I saw that as a bit of duplication. I figured that
> most people are just copying Altera's devkit schematic, that if a new
> board file shows up that has a different controllable regulator, then
> the board file can have the new regulator node. Meanwhile, this patch
> saves adding an additional regulator node for the existing board files.
>
> The 3.3V is not just used by MMC, but the for all 3.3V peripherals.

The advantage of putting it in each board file is you could name it
based on the schematics.  I see SoCKit_RevC it is named "VCC3P3"

It also allows you to specify the 3.3 supply as the output of a real
regulator driver.  In s5_soc_devkit it looks like this comes from
LTC2978.  That's got i2c connections.  What happens when you add a
driver for that?