[PATCH] ARM: dts: Add mask-tpm-reset to the device tree

[Doug Anderson]

Tomasz,

On Fri, Jun 27, 2014 at 8:14 AM, Tomasz Figa <tomasz.figa at gmail.com> wrote:
> On 27.06.2014 17:10, Doug Anderson wrote:
>> Tomasz and Vikas,
>>
>> On Fri, Jun 27, 2014 at 5:17 AM, Tomasz Figa <tomasz.figa at gmail.com> wrote:
>>> Hi Doug,
>>>
>>> On 26.06.2014 17:25, Doug Anderson wrote:
>>>> Tomasz,
>>>>
>>>> On Thu, Jun 26, 2014 at 2:52 AM, Tomasz Figa <t.figa at samsung.com> wrote:
>>>>> Hi Vikas, Doug,
>>>>>
>>>>> On 26.06.2014 11:15, Vikas Sajjan wrote:
>>>>>> From: Doug Anderson <dianders at chromium.org>
>>>>>>
>>>>>> The mask-tpm-reset GPIO is used by the kernel to prevent the TPM from
>>>>>> being reset across sleep/wake.  If we don't set it to anything then
>>>>>> the TPM will be reset.  U-Boot will detect this as invalid
>>>>>> and will reset the system on resume time. This GPIO can always be low
>>>>>> and not hurt anything.  It will get pulled back high again during a
>>>>>> normal warm reset when it will default back to an input.
>>>>>>
>>>>>> To properly preserve the TPM state across suspend/resume and to make
>>>>>> the chrome U-Boot happy, properly set the GPIO to mask the
>>>>>> reset to the TPM.
>>>>>>
>>>>>> Signed-off-by: Doug Anderson <dianders at chromium.org>
>>>>>> Signed-off-by: Vikas Sajjan <vikas.sajjan at samsung.com>
>>>>>> ---
>>>>>>  arch/arm/boot/dts/exynos5420-peach-pit.dts |   20 ++++++++++++++++++++
>>>>>>  1 file changed, 20 insertions(+)
>>>>>>
>>>>>> diff --git a/arch/arm/boot/dts/exynos5420-peach-pit.dts b/arch/arm/boot/dts/exynos5420-peach-pit.dts
>>>>>> index 7649982..8fd990a 100644
>>>>>> --- a/arch/arm/boot/dts/exynos5420-peach-pit.dts
>>>>>> +++ b/arch/arm/boot/dts/exynos5420-peach-pit.dts
>>>>>> @@ -87,6 +87,18 @@
>>>>>>               pinctrl-0 = <&usb301_vbus_en>;
>>>>>>               enable-active-high;
>>>>>>       };
>>>>>> +
>>>>>> +     /* We need GPX0_6 to be low at sleep time; just keep it low always */
>>>>>> +     mask_tpm_reset_regulator: mask-tpm-reset-regulator {
>>>>>> +     compatible = "regulator-fixed";
>>>>>> +     regulator-name = "mask-tpm-reset ";
>>>>>> +             gpio = <&gpx0 6 0>;
>>>>>> +             enable-active-low;
>>>>>> +             regulator-boot-on;
>>>>>> +             regulator-always-on;
>>>>>> +             pinctrl-names = "default";
>>>>>> +             pinctrl-0 = <&mask_tpm_reset>;
>>>>>> +     };
>>>>>
>>>>> I don't think this pin is supposed to be a real regulator. If I'm right,
>>>>> you should just add a hog for it, if you don't have a proper driver to
>>>>> handle it.
>>>>
>>>> Yes, I agree that it shouldn't really be a regulator, but there's not
>>>> a whole lot of choice.  The pin needs to actually be driven low, not
>>>> just pulled low.  Without your proposed patch (pinctrl: samsung: Allow
>>>> pin value to be initialized using pinfunc) I don't think it's possible
>>>> to actually drive a pin low with a hog.  I could be wrong, though.
>>>>
>>>
>>> Uhm, I was convinced that this patch was already in. So I think your use
>>> case is definitely a good reason to get back to this patch and use the
>>> facility it provides to solve your problem.
>>
>> Thanks, that seems very reasonable to me, too.
>>
>> Are you going to pick up revitalizing this patch series or are you
>> hoping Vikas will?  IIRC I was in favor of your patch but it generated
>> a whole bunch of discussion and never actually landed.
>
> I will respin it along with few other patches for pinctrl-samsung, but
> obviously not before Monday.

Sounds like a plan.  Vikas: I'll assume you're going to redo this
patch atop Tomasz's once he posts up his.

-Doug