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

[Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx>]

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".

> Nice to expand on that in the commit message and maybe even
> a comment in the code. They look like they are all Bluetooth
> and GPS related.
> 
> Mika writes:
> 
> > I don't think we should expose these unless there is some real reason to
> > do so. These pins are pretty much internal to the SoC in Gemini Lake.
> 
> In what sense are they "internal"?
> 
> There are many, many precedents of SoCs exposing pins and pin groups
> for  Bluetooth and GPS in the pin control subsystem. If people build
> systems, knowing how hardware engineers think, and since pins
> are a scarcity, they will in short time do the following:

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.

> +       PINCTRL_PIN(88, "vCNV_BT_UART_CTS_B"),
> +       PINCTRL_PIN(89, "vCNV_BT_UART_RTS_B"),
> (...)
> +       PINCTRL_PIN(92, "vCNV_MFUART1_CTS_B"),
> +       PINCTRL_PIN(93, "vCNV_MFUART1_RTS_B"),
> (...)
> +       PINCTRL_PIN(96, "vCNV_GNSS_UART_CTS_B"),
> +       PINCTRL_PIN(97, "vCNV_GNSS_UART_RTS_B"),
> (...)
> +       PINCTRL_PIN(100, "vLPSS_UART0_CTS_B"),
> +       PINCTRL_PIN(101, "vLPSS_UART0_RTS_B"),
> (...)
> +       PINCTRL_PIN(104, "vLPSS_UART1_CTS_B"),
> +       PINCTRL_PIN(105, "vLPSS_UART1_RTS_B"),
> 
> "Oh we don't use those CTS/RTS pins, let's reuse them for LEDs
> and buttons"
> 
> That is what hardware engineers to 9 times out of 10.

I agree but in this case it is really not possible to connect anything
to those pins ;-)