Re: [PATCH] ARM: tegra: Enable TPM on tegra124 nyan boards

[Stephen Warren <swarren-3lzwWm7+Weoh9ZMKESR00Q@public.gmane.org>]

On 05/14/2015 07:09 AM, Tomeu Vizoso wrote:
> On 13 May 2015 at 16:45, Stephen Warren <swarren-3lzwWm7+Weoh9ZMKESR00Q@public.gmane.org> wrote:
>> On 05/13/2015 08:13 AM, Simon Glass wrote:
>>>
>>> Regenerate the pinmux from the latest tegra-pinmux-scripts.
>>
>>
>> (Dropping most CCs; DT maintainers and lists generally don't get CC'd on
>> simple DT content changes but rather on schema adds/changes and perhaps
>> major DT content changes depending on context)
>>
>>> diff --git a/arch/arm/boot/dts/tegra124-nyan-big.dts
>>> b/arch/arm/boot/dts/tegra124-nyan-big.dts
>>
>>
>>>                  pinctrl-names = "default";
>>>                  pinctrl-0 = <&pinmux_default>;
>>>
>>> -               pinmux_default: common {
>>> +               state_default: pinmux {
>>
>>
>> This change will break compilation, since it changes the label name, yet the
>> old name is still referenced in pinctrl-0 above. Same applies in the other
>> file too.
>>
>>> diff --git a/arch/arm/boot/dts/tegra124-nyan-blaze.dts
>>> b/arch/arm/boot/dts/tegra124-nyan-blaze.dts
>>
>>
>>> @@ -437,18 +437,18 @@
>>>                          usb_vbus_en0_pn4 {
>>>                                  nvidia,pins = "usb_vbus_en0_pn4";
>>>                                  nvidia,function = "usb";
>>> -                               nvidia,pull = <TEGRA_PIN_PULL_UP>;
>>> +                               nvidia,pull = <TEGRA_PIN_PULL_NONE>;
>>>                                  nvidia,tristate = <TEGRA_PIN_DISABLE>;
>>>                                  nvidia,enable-input = <TEGRA_PIN_ENABLE>;
>>> -                               nvidia,open-drain = <TEGRA_PIN_DISABLE>;
>>> +                               nvidia,open-drain = <TEGRA_PIN_ENABLE>;
>>>                          };
>>>                          usb_vbus_en1_pn5 {
>>>                                  nvidia,pins = "usb_vbus_en1_pn5";
>>>                                  nvidia,function = "usb";
>>> -                               nvidia,pull = <TEGRA_PIN_PULL_UP>;
>>> +                               nvidia,pull = <TEGRA_PIN_PULL_NONE>;
>>>                                  nvidia,tristate = <TEGRA_PIN_DISABLE>;
>>>                                  nvidia,enable-input = <TEGRA_PIN_ENABLE>;
>>> -                               nvidia,open-drain = <TEGRA_PIN_DISABLE>;
>>> +                               nvidia,open-drain = <TEGRA_PIN_ENABLE>;
>>>                          };
>>
>>
>> Tomeu, can you comment on those changes? Evidently the pinmux configuration
>> that's you added to the kernel doesn't exactly match the pinmux
>> configuration that you added to tegra-pinmux-scripts.
>
> Are you sure? Just checked and what tegra-pinmux-scripts currently
> generates matches what is currently in the kernel, for both nyans.

My apologies; you're correct.

This patch to the kernel DTs includes changes that aren't generated by 
either current tegra-pinmux-scripts, nor by tegra-pinmux-scripts with 
Simon's "[pinmux scripts PATCH] Support TPM on nyan boards" applied. 
Simon, can you double-check you didn't have any local patches to 
tegra-pinmux-scripts applied when you generated the DT content for this 
patch?

>> Is the change above
>> correct, or do we need to propagate this change from the kernel DT into
>> tegra-pinmux-scripts, and hence also into the U-Boot pinmux setup table?
>>
>> My understanding of how these pins are generally used is that open-drain is
>> likely correct. I have no idea whether Tegra should supply the pullup for
>> these pins, or whether the board has a pullup resistor in which case Tegra
>> doesn't need to pull up.
>
>  From what Andrew (added to CC) said when these changes were discussed,
> it shouldn't matter as a fixed regulator is used to drive those pins
> high.

It looks like nyan-big and nyan-blaze configure these pins differently, 
which may be incorrect if the boards are truly almost identical. Is that 
expected? Nyan-big sets them both to open-drain but Nyan-blaze sets them 
to push-pull. The pull-up enable is different too. Typically these pins 
are open-drain, because there's often a current sensor chip on the USB 
port power rail which asserts (pulls low in open-drain mode) these 
signals to turn off the power when an over-current condition is 
detected. Not all boards do this though, so the difference may be 
perfectly expected; someone with access to the schematics would have to 
check.