Re: [PATCH 00/11] pinctrl: sh-pfc: Convert to new non-GPIO helper macros

[Geert Uytterhoeven <geert@linux-m68k.org>]

On Mon, May 13, 2019 at 5:29 PM Geert Uytterhoeven
<geert+renesas@glider.be> wrote:
> On many Renesas ARM SoCs, there exist pins that are not associated with
> a GPIO port, but still need configuration (e.g. drive strength or
> pull-up).  While pins with GPIO functionality are indexed by their
> GPIO number, no such number exists for non-GPIO pins.  Hence for the
> latter, the pin control driver uses numbers outside the GPIO number
> space, derived from the row and column numbers of the physical pins.
>
> For R-Car H3 (and later M3-W and M3-N), the choice was made to use the
> SiP (System-in-Package, i.e. SoC + RAM + HyperFlash in a BGA package)
> physical pin numbers, as the SiP was what was mounted on the
> Salvator-X(S) and ULCB development boards available at that time.
>
> In hindsight, it would have been better to settle on the SoC physical
> pin numbers, though: the pin control driver for R-Car M3-W was reused
> for the RZ/G2M SoC, which is only available as an SoC, not SiP, thus
> making it hard to match the driver with the documentation.
>
> But even for SoCs there can be confusion: several SoCs are available in
> multiple packages, with the same or different number of pins, leading to
> different pin numberings.
>
> As this numbering is used only internal to the driver, and pin control
> configuration from DT refers to these pins by signal name, not pin
> number (usually, see exceptions below[*]), I started wondering if we
> could get rid of the SoC/SiP pin numbers instead.  As the actual numbers
> don't matter, all that is needed for the driver is a unique number for
> each pin.
>
> Hence this patch series converts the affected drivers to use new macros
> that allow to describe pins without GPIO functionality, and refer to
> them by auto-generated symbolic enum values, similar in spirit to the
> existing scheme for handling pins with GPIO functionality.
>
> This series consists of three parts:
>   - Patch 1 introduces new macros to describe and handle pins without
>     GPIO functionality,
>   - Patches 2-10 convert the pin control drivers for the individual SoCs
>     to use the new macros,
>   - Patch 11 removes the now unused old macros.
>
> There should be no functional changes induced by this patch series,
> which has been tested on Salvator-X(S) (with R-Car H3 ES1.0 and ES2.0,
> M3-W, and M3-N), Ebisu (R-Car E3), and KZM-A9-GT (SH-Mobile AG5).
>
> [*] The user-visible names of pins without GPIO functionality are based
>     on pin numbers (e.g. "B25") instead of signal names ("CLKOUT") on
>     EMMA Mobile EV2, R-Car M1A, R-Car H2, and SH-Mobile AG5.
>     I didn't change these to preserve DT backwards compatibility.

Queueing in sh-pfc-for-v5.3.

> The "name" parameters of the PIN_NOGP_CFG() and PIN_NOGP() macros could
> be removed, if these macros would generate the names from the "pin"
> parameters.  However, that would:
>   1. Require replacing the "#" suffices in pin names for active-low
>      signals by "_N",
>      R-Car H3/M3-W/M3-N use a "#" suffix, R-Car E3 use a "_N" suffix.
>   2. Replace the names based on pin numbers on older SoCs by signal
>      names.
> Both changes could affect DT backwards compatibility.  None of these are
> currently used in (upstream) DTS files, though.
> Do you think it would be worthwhile to make this consistent?

We can still break backwards compatibility later ;-)

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds