linux-kernel - Re: [PATCH v4 12/15] pinctrl: Add AXP192 pin control driver

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Message-ID: <oMIjFujkw4ZeuMGoTkWq64BbfEejJF12@localhost>
Date:   Fri, 01 Jul 2022 16:37:45 +0100
From:   Aidan MacDonald <aidanmacdonald.0x0@...il.com>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     Linus Walleij <linus.walleij@...aro.org>,
        Bartosz Golaszewski <brgl@...ev.pl>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Chen-Yu Tsai <wens@...e.org>,
        Jonathan Cameron <jic23@...nel.org>,
        Sebastian Reichel <sre@...nel.org>,
        Lee Jones <lee.jones@...aro.org>,
        Liam Girdwood <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>,
        Lars-Peter Clausen <lars@...afoo.de>, quic_gurus@...cinc.com,
        Sebastian Reichel <sebastian.reichel@...labora.com>,
        Michael Walle <michael@...le.cc>,
        Randy Dunlap <rdunlap@...radead.org>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        devicetree <devicetree@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-iio <linux-iio@...r.kernel.org>,
        Linux PM <linux-pm@...r.kernel.org>
Subject: Re: [PATCH v4 12/15] pinctrl: Add AXP192 pin control driver


Andy Shevchenko <andy.shevchenko@...il.com> writes:

> On Wed, Jun 29, 2022 at 4:30 PM Aidan MacDonald
> <aidanmacdonald.0x0@...il.com> wrote:
>>
>> The AXP192 PMIC's GPIO registers are much different from the GPIO
>> registers of the AXP20x and AXP813 PMICs supported by the existing
>> pinctrl-axp209 driver. It makes more sense to add a new driver for
>> the AXP192, rather than add support in the existing axp20x driver.
>>
>> The pinctrl-axp192 driver is considerably more flexible in terms of
>> register layout and should be able to support other X-Powers PMICs.
>> Interrupts and pull down resistor configuration are supported too.
>
> ...
>
>> +config PINCTRL_AXP192
>> +       tristate "X-Powers AXP192 PMIC pinctrl and GPIO Support"
>> +       depends on MFD_AXP20X
>> +       select PINMUX
>> +       select GENERIC_PINCONF
>> +       select GPIOLIB
>> +       help
>> +         AXP PMICs provide multiple GPIOs that can be muxed for different
>> +         functions. This driver bundles a pinctrl driver to select the function
>> +         muxing and a GPIO driver to handle the GPIO when the GPIO function is
>> +         selected.
>> +         Say Y to enable pinctrl and GPIO support for the AXP192 PMIC.
>
> What will be the module name if compiled as a module?
>
> ...
>
>> +/**
>> + * struct axp192_pctl_function - describes a function that GPIOs may have
>> + *
>> + * @name: Function name
>> + * @muxvals: Mux values used for selecting this function, one per GPIO.
>> + *           The i'th element corresponds to the i'th GPIO and is written
>> + *           to the GPIO's control register field to select this function.
>> + *           U8_MAX indicates that the pin does not support this function.
>> + * @groups: Array of @ngroups groups listing pins supporting this function.
>> + * @ngroups: Number of pin groups.
>> + */
>> +struct axp192_pctl_function {
>> +       const char              *name;
>> +       /* Mux value written to the control register to select the function (-1 if unsupported) */
>> +       const u8                *muxvals;
>> +       const char * const      *groups;
>> +       unsigned int            ngroups;
>> +};
>
> Can it be replaced by struct function_desc?
> https://elixir.bootlin.com/linux/latest/source/drivers/pinctrl/pinmux.h#L130

That'd work, but using the generic infrastructure doesn't allow me to
simplify anything -- I can eliminate three trivial functions, but the
generic code is higher overhead (extra allocations, radix trees, ...)
so I'd prefer to stick with the current approach.

>> +       ret = devm_gpiochip_add_data(dev, &pctl->chip, pctl);
>> +       if (ret)
>> +               dev_err_probe(dev, ret, "Failed to register GPIO chip\n");
>
> Missed return.

Thanks for catching this, that was pretty silly of me...