Re: [PATCH v1 2/4] pinctrl: geminilake: Add vGPIO pins

[Linus Walleij <linus.walleij@xxxxxxxxxx>]

On Tue, Oct 16, 2018 at 9:28 AM Mika Westerberg
<mika.westerberg@xxxxxxxxxxxxxxx> wrote:
> On Tue, Oct 16, 2018 at 09:25:02AM +0200, Linus Walleij wrote:
> > On Thu, Oct 4, 2018 at 5:33 PM Andy Shevchenko
> > <andriy.shevchenko@xxxxxxxxxxxxxxx> wrote:
> >
> > > Intel Gemini Lake provides vGPIO pins which are now missed from the list.
> > > Add them here.
> > >
> > > Signed-off-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
> >
> > What does the "v" in "vGPIO" stand for?
>
> It stands for "virtual".
(...)
> These pins are not exposed externally (e.g there is no physical pin for
> thse), just internal so there is no way to connect anything to them.

Ah but it is really pin control, because what you say is that on
Gemini Lake there are several chips inside the package, and this
pertains to pads bonded directly over to another chip, right?

Or even a line of polysilicon over to another part of the same chip
die, but I doubt that since BT and GPS would give interesting
radio interference with the CPU parts (no idea how smart your
silicon people are though, I think they are pretty smart so who
knows!)

In either case, none of that is "virtual" it's pretty physical. The
electrons still pass through a medium. Virtual is a bad name
for this.

I guess I would still add them if they had some interesting electronic
properties that you have to change though, like setting drive strength,
that BlueTooth of GPS needs.

I would assume that they are set up by either hardware defaults
or ROM/BIOS, but you know: someone writing the ROM/BIOS
will get it wrong and it needs to be reconfigured. Or reconfigured
just to save power for some usecase. This always happens in
my experience, I would not be surprised if some Intel customer
has code for doing exactly that in their vendor tree (because I
have seen so much of that stuff before).

But until proven wrong, I can agree to keep this out of tree.

I just wanted to give Andy some credit for exposing this, in
most cases it actually makes sense to just expose all buttons.

Yours,
Linus Walleij