Re: [PATCH 0/2] GPIO support for Socionext Synquacer

[Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>]

On 31 October 2017 at 12:20, Linus Walleij <linus.walleij@xxxxxxxxxx> wrote:
> On Fri, Oct 27, 2017 at 10:21 PM, Ard Biesheuvel
> <ard.biesheuvel@xxxxxxxxxx> wrote:
>
>> The Socionext Synquacer SC2A11, which is used in the arm64 Developer Box,
>> shares its GPIO IP with a Fujitsu SoC for which we already have support
>> in the tree. So let's tweak it so that we can reuse it.
>>
>> Cc: Linus Walleij <linus.walleij@xxxxxxxxxx>
>>
>> Ard Biesheuvel (2):
>>   gpio: mb86s7x: share with other SoCs as module
>>   gpio: mb86s70: Revert "Return error if requesting an already assigned
>>     gpio"
>
> Nice. We might need to look into the following wrt this driver:
>
> - Using generic MMIO GPIO, i.e. select GPIO_GENERIC in Kconfig
>   and a patch such as commit 6d125412fc16802012a17665638f49b0b0c81f18
>   "gpio: iop: Use generic GPIO MMIO functions for driver"
>   apart from reduced code size this brings the .get_multiple() and
>   .set_multiple() callbacks for FREE.
>   The fact that the driver is so simple that it should have been using
>   MMIO/GENERIC GPIO is a plain oversight during review.
>

Does this work with the layout if this chip? It has 32 GPIO lines,
whose controls are mapped onto the lowest 8 bits of 4 adjacent 32-bit
registers.

> - When submitting the DTS for that developer box, make sure that
>   the 96boards header has proper GPIO line names from day 1,
>   see e.g.
>   commit bbaf867e2d3796bca465d07ffcd800a3bd570861
>   "arm64: dts: hikey: name the GPIO lines"
>

I currently have this in my DTS:

&gpio {
    dsw3_1 {
        gpios = <0 GPIO_ACTIVE_HIGH>;
        gpio-hog;
        input;
    };

    dsw3_2 {
        gpios = <1 GPIO_ACTIVE_HIGH>;
        gpio-hog;
        input;
    };

    dsw3_3 {
        gpios = <2 GPIO_ACTIVE_HIGH>;
        gpio-hog;
        input;
    };

    dsw3_4 {
        gpios = <3 GPIO_ACTIVE_HIGH>;
        gpio-hog;
        input;
    };

    dsw3_5 {
        gpios = <4 GPIO_ACTIVE_HIGH>;
        gpio-hog;
        input;
    };

    dsw3_6 {
        gpios = <5 GPIO_ACTIVE_HIGH>;
        gpio-hog;
        input;
    };

    dsw3_7 {
        gpios = <6 GPIO_ACTIVE_HIGH>;
        gpio-hog;
        input;
    };

    dsw3_8 {
        gpios = <7 GPIO_ACTIVE_HIGH>;
        gpio-hog;
        input;
    };

for the 8 DIP switches that are connected to GPIO lines. There are
more assigned, to various function, and 8 of them are routed to the
96boards low speed connector as well.

> Ard: if you have this machine on your desk help with the above would
> be much appreciated (plus it's fun!) thanks a bunch :)
>

Of course, if you help me understand it :-)

So I can add the names for all the lines that have a purpose, but is
that orthogonal to hogging?
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