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

[Linus Walleij <linus.walleij@xxxxxxxxxx>]

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?

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:

+       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.

Yours,
Linus Walleij