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Date:   Fri, 8 Jul 2022 19:31:47 +0200
From:   Henning Schild <henning.schild@siemens.com>
To:     Bartosz Golaszewski <brgl@bgdev.pl>
Cc:     Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@vger.kernel.org>,
        Linus Walleij <linus.walleij@linaro.org>,
        Tasanakorn Phaipool <tasanakorn@gmail.com>,
        Sheng-Yuan Huang <syhuang3@nuvoton.com>,
        Kuan-Wei Ho <cwho@nuvoton.com>,
        Andy Shevchenko <andy.shevchenko@gmail.com>
Subject: Re: [PATCH v2 1/1] gpio: nct6116d: add new driver for several
 Nuvoton super io chips
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References: <20220704130602.12307-1-henning.schild@siemens.com>
        <20220704130602.12307-2-henning.schild@siemens.com>
        <CAMRc=MeJ4LiYkCDScGBhnaDbxQsHQ8T9R2MwGOy6Ju=tkWdzXw@mail.gmail.com>
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Am Fri, 8 Jul 2022 18:00:27 +0200
schrieb Bartosz Golaszewski <brgl@bgdev.pl>:

> On Mon, Jul 4, 2022 at 3:06 PM Henning Schild
> <henning.schild@siemens.com> wrote:
> >
> > This patch adds gpio support for several Nuvoton NCTXXX chips. These
> > Super-I/O chips offer multiple functions of which several already
> > have drivers in the kernel, i.e. hwmon and watchdog.
> >
> > Signed-off-by: Henning Schild <henning.schild@siemens.com>
> > ---
> >  drivers/gpio/Kconfig         |   9 +
> >  drivers/gpio/Makefile        |   1 +
> >  drivers/gpio/gpio-nct6116d.c | 412
> > +++++++++++++++++++++++++++++++++++ 3 files changed, 422
> > insertions(+) create mode 100644 drivers/gpio/gpio-nct6116d.c
> >
> > diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig
> > index b01961999ced..40f1494b1adc 100644
> > --- a/drivers/gpio/Kconfig
> > +++ b/drivers/gpio/Kconfig
> > @@ -457,6 +457,15 @@ config GPIO_MXS
> >         select GPIO_GENERIC
> >         select GENERIC_IRQ_CHIP
> >
> > +config GPIO_NCT6116D
> > +       tristate "Nuvoton Super-I/O GPIO support"
> > +       help
> > +         This option enables support for GPIOs found on Nuvoton
> > Super-I/O
> > +         chips NCT5104D, NCT6106D, NCT6116D, NCT6122D.
> > +
> > +         To compile this driver as a module, choose M here: the
> > module will
> > +         be called gpio-nct6116d.
> > +
> >  config GPIO_OCTEON
> >         tristate "Cavium OCTEON GPIO"
> >         depends on CAVIUM_OCTEON_SOC
> > diff --git a/drivers/gpio/Makefile b/drivers/gpio/Makefile
> > index 14352f6dfe8e..87f1b0a0cda2 100644
> > --- a/drivers/gpio/Makefile
> > +++ b/drivers/gpio/Makefile
> > @@ -107,6 +107,7 @@ obj-$(CONFIG_GPIO_MT7621)           +=
> > gpio-mt7621.o obj-$(CONFIG_GPIO_MVEBU)               += gpio-mvebu.o
> >  obj-$(CONFIG_GPIO_MXC)                 += gpio-mxc.o
> >  obj-$(CONFIG_GPIO_MXS)                 += gpio-mxs.o
> > +obj-$(CONFIG_GPIO_NCT6116D)            += gpio-nct6116d.o
> >  obj-$(CONFIG_GPIO_OCTEON)              += gpio-octeon.o
> >  obj-$(CONFIG_GPIO_OMAP)                        += gpio-omap.o
> >  obj-$(CONFIG_GPIO_PALMAS)              += gpio-palmas.o
> > diff --git a/drivers/gpio/gpio-nct6116d.c
> > b/drivers/gpio/gpio-nct6116d.c new file mode 100644
> > index 000000000000..6c277636c773
> > --- /dev/null
> > +++ b/drivers/gpio/gpio-nct6116d.c
> > @@ -0,0 +1,412 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +/*
> > + * GPIO driver for Nuvoton Super-I/O chips NCT5104D, NCT6106D,
> > NCT6116D, NCT6122D
> > + *
> > + * Authors:
> > + *  Tasanakorn Phaipool <tasanakorn@gmail.com>
> > + *  Sheng-Yuan Huang <syhuang3@nuvoton.com>
> > + *  Kuan-Wei Ho <cwho@nuvoton.com>
> > + *  Henning Schild <henning.schild@siemens.com>
> > + */
> > +
> > +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
> > +
> > +#include <linux/gpio/driver.h>
> > +#include <linux/init.h>
> > +#include <linux/io.h>
> > +#include <linux/module.h>
> > +#include <linux/platform_device.h>
> > +
> > +/*
> > + * Super-I/O registers
> > + */
> > +#define SIO_LDSEL              0x07    /* Logical device select */
> > +#define SIO_CHIPID             0x20    /* Chaip ID (2 bytes) */
> > +#define SIO_GPIO_ENABLE                0x30    /* GPIO enable */
> > +
> > +#define SIO_LD_GPIO            0x07    /* GPIO logical device */
> > +#define SIO_UNLOCK_KEY         0x87    /* Key to enable Super-I/O
> > */ +#define SIO_LOCK_KEY           0xAA    /* Key to disable
> > Super-I/O */ +
> > +#define SIO_ID_MASK            GENMASK(15, 4)
> > +#define SIO_NCT5104D_ID                0x1061
> > +#define SIO_NCT6106D_ID                0xC452
> > +#define SIO_NCT6116D_ID                0xD282
> > +#define SIO_NCT6122D_ID                0xD2A3
> > +
> > +enum chips {
> > +       nct5104d,
> > +       nct6106d,
> > +       nct6116d,
> > +       nct6122d,
> > +};
> > +
> > +static const char * const nct6116d_names[] = {
> > +       [nct5104d] = "nct5104d",
> > +       [nct6106d] = "nct6106d",
> > +       [nct6116d] = "nct6116d",
> > +       [nct6122d] = "nct6122d",
> > +};
> > +
> > +struct nct6116d_sio {
> > +       int addr;
> > +       enum chips type;
> > +};
> > +
> > +struct nct6116d_gpio_bank {
> > +       struct gpio_chip chip;
> > +       unsigned int regbase;
> > +       struct nct6116d_gpio_data *data;
> > +};
> > +
> > +struct nct6116d_gpio_data {
> > +       struct nct6116d_sio *sio;
> > +       int nr_bank;
> > +       struct nct6116d_gpio_bank *bank;
> > +};
> > +
> > +/*
> > + * Super-I/O functions.
> > + */
> > +
> > +static inline int superio_inb(int base, int reg)
> > +{
> > +       outb(reg, base);
> > +       return inb(base + 1);
> > +}
> > +
> > +static int superio_inw(int base, int reg)
> > +{
> > +       int val;
> > +
> > +       outb(reg++, base);
> > +       val = inb(base + 1) << 8;
> > +       outb(reg, base);
> > +       val |= inb(base + 1);
> > +
> > +       return val;
> > +}
> > +
> > +static inline void superio_outb(int base, int reg, int val)
> > +{
> > +       outb(reg, base);
> > +       outb(val, base + 1);
> > +}
> > +
> > +static inline int superio_enter(int base)
> > +{
> > +       /* Don't step on other drivers' I/O space by accident. */
> > +       if (!request_muxed_region(base, 2, KBUILD_MODNAME)) {
> > +               pr_err("I/O address 0x%04x already in use\n", base);
> > +               return -EBUSY;
> > +       }
> > +
> > +       /* According to the datasheet the key must be send twice. */
> > +       outb(SIO_UNLOCK_KEY, base);
> > +       outb(SIO_UNLOCK_KEY, base);
> > +
> > +       return 0;
> > +}
> > +
> > +static inline void superio_select(int base, int ld)
> > +{
> > +       outb(SIO_LDSEL, base);
> > +       outb(ld, base + 1);
> > +}
> > +
> > +static inline void superio_exit(int base)
> > +{
> > +       outb(SIO_LOCK_KEY, base);
> > +       release_region(base, 2);
> > +}
> > +
> > +/*
> > + * GPIO chip.
> > + */
> > +
> > +#define gpio_dir(base) ((base) + 0)
> > +#define gpio_data(base) ((base) + 1)
> > +
> > +static inline void *nct6116d_to_gpio_bank(struct gpio_chip *chip)
> > +{
> > +       return container_of(chip, struct nct6116d_gpio_bank, chip);
> > +}
> > +
> > +static int nct6116d_gpio_get_direction(struct gpio_chip *chip,
> > unsigned int offset) +{
> > +       struct nct6116d_gpio_bank *bank =
> > nct6116d_to_gpio_bank(chip);
> > +       struct nct6116d_sio *sio = bank->data->sio;
> > +       int err;
> > +       u8 dir;
> > +
> > +       err = superio_enter(sio->addr);
> > +       if (err)
> > +               return err;
> > +       superio_select(sio->addr, SIO_LD_GPIO);
> > +
> > +       dir = superio_inb(sio->addr, gpio_dir(bank->regbase));
> > +
> > +       superio_exit(sio->addr);
> > +
> > +       if (dir & 1 << offset)
> > +               return GPIO_LINE_DIRECTION_OUT;
> > +
> > +       return GPIO_LINE_DIRECTION_IN;
> > +}
> > +
> > +static int nct6116d_gpio_direction_in(struct gpio_chip *chip,
> > unsigned int offset) +{
> > +       struct nct6116d_gpio_bank *bank =
> > nct6116d_to_gpio_bank(chip);
> > +       struct nct6116d_sio *sio = bank->data->sio;
> > +       int err;
> > +       u8 dir;
> > +
> > +       err = superio_enter(sio->addr);
> > +       if (err)
> > +               return err;
> > +       superio_select(sio->addr, SIO_LD_GPIO);
> > +
> > +       dir = superio_inb(sio->addr, gpio_dir(bank->regbase));
> > +       dir |= BIT(offset);
> > +       superio_outb(sio->addr, gpio_dir(bank->regbase), dir);
> > +
> > +       superio_exit(sio->addr);
> > +
> > +       return 0;
> > +}
> > +
> > +static int nct6116d_gpio_get(struct gpio_chip *chip, unsigned int
> > offset) +{
> > +       struct nct6116d_gpio_bank *bank =
> > nct6116d_to_gpio_bank(chip);
> > +       struct nct6116d_sio *sio = bank->data->sio;
> > +       int err;
> > +       u8 data;
> > +
> > +       err = superio_enter(sio->addr);
> > +       if (err)
> > +               return err;
> > +       superio_select(sio->addr, SIO_LD_GPIO);
> > +
> > +       data = superio_inb(sio->addr, gpio_data(bank->regbase));
> > +
> > +       superio_exit(sio->addr);
> > +
> > +       return !!(data & BIT(offset));
> > +}
> > +
> > +static int nct6116d_gpio_direction_out(struct gpio_chip *chip,
> > +                                    unsigned int offset, int value)
> > +{
> > +       struct nct6116d_gpio_bank *bank =
> > nct6116d_to_gpio_bank(chip);
> > +       struct nct6116d_sio *sio = bank->data->sio;
> > +       u8 dir, data_out;
> > +       int err;
> > +
> > +       err = superio_enter(sio->addr);
> > +       if (err)
> > +               return err;
> > +       superio_select(sio->addr, SIO_LD_GPIO);
> > +
> > +       data_out = superio_inb(sio->addr, gpio_data(bank->regbase));
> > +       if (value)
> > +               data_out |= BIT(offset);
> > +       else
> > +               data_out &= ~BIT(offset);
> > +       superio_outb(sio->addr, gpio_data(bank->regbase), data_out);
> > +
> > +       dir = superio_inb(sio->addr, gpio_dir(bank->regbase));
> > +       dir &= ~BIT(offset);
> > +       superio_outb(sio->addr, gpio_dir(bank->regbase), dir);
> > +
> > +       superio_exit(sio->addr);
> > +
> > +       return 0;
> > +}
> > +
> > +static void nct6116d_gpio_set(struct gpio_chip *chip, unsigned int
> > offset, int value) +{
> > +       struct nct6116d_gpio_bank *bank =
> > nct6116d_to_gpio_bank(chip);
> > +       struct nct6116d_sio *sio = bank->data->sio;
> > +       u8 data_out;
> > +       int err;
> > +
> > +       err = superio_enter(sio->addr);
> > +       if (err)
> > +               return;
> > +       superio_select(sio->addr, SIO_LD_GPIO);
> > +
> > +       data_out = superio_inb(sio->addr, gpio_data(bank->regbase));
> > +       if (value)
> > +               data_out |= BIT(offset);
> > +       else
> > +               data_out &= ~BIT(offset);
> > +       superio_outb(sio->addr, gpio_data(bank->regbase), data_out);
> > +
> > +       superio_exit(sio->addr);
> > +}
> > +
> > +#define NCT6116D_GPIO_BANK(_base, _ngpio, _regbase, _label)
> >             \
> > +       {
> >             \
> > +               .chip = {
> >             \
> > +                       .label            = _label,
> >             \
> > +                       .owner            = THIS_MODULE,
> >             \
> > +                       .get_direction    =
> > nct6116d_gpio_get_direction,        \
> > +                       .direction_input  =
> > nct6116d_gpio_direction_in,         \
> > +                       .get              = nct6116d_gpio_get,
> >             \
> > +                       .direction_output =
> > nct6116d_gpio_direction_out,        \
> > +                       .set              = nct6116d_gpio_set,
> >             \
> > +                       .base             = _base,
> >             \
> > +                       .ngpio            = _ngpio,
> >             \
> > +                       .can_sleep        = false,
> >             \
> > +               },
> >             \
> > +               .regbase = _regbase,
> >             \
> > +       }
> > +
> > +static struct nct6116d_gpio_bank nct6116d_gpio_bank[] = {
> > +       NCT6116D_GPIO_BANK(0, 8, 0xE0, KBUILD_MODNAME "-0"),
> > +       NCT6116D_GPIO_BANK(10, 8, 0xE4, KBUILD_MODNAME "-1"),
> > +       NCT6116D_GPIO_BANK(20, 8, 0xE8, KBUILD_MODNAME "-2"),
> > +       NCT6116D_GPIO_BANK(30, 8, 0xEC, KBUILD_MODNAME "-3"),
> > +       NCT6116D_GPIO_BANK(40, 8, 0xF0, KBUILD_MODNAME "-4"),
> > +};
> > +
> > +/*
> > + * Platform device and driver.
> > + */
> > +
> > +static int nct6116d_gpio_probe(struct platform_device *pdev)
> > +{
> > +       struct nct6116d_sio *sio = pdev->dev.platform_data;
> > +       struct nct6116d_gpio_data *data;
> > +       int err;
> > +       int i;
> > +
> > +       data = devm_kzalloc(&pdev->dev, sizeof(*data), GFP_KERNEL);
> > +       if (!data)
> > +               return -ENOMEM;
> > +
> > +       data->nr_bank = ARRAY_SIZE(nct6116d_gpio_bank);
> > +       data->bank = nct6116d_gpio_bank;
> > +       data->sio = sio;
> > +
> > +       platform_set_drvdata(pdev, data);
> > +
> > +       /* For each GPIO bank, register a GPIO chip. */
> > +       for (i = 0; i < data->nr_bank; i++) {
> > +               struct nct6116d_gpio_bank *bank = &data->bank[i];
> > +
> > +               bank->chip.parent = &pdev->dev;
> > +               bank->data = data;
> > +
> > +               err = devm_gpiochip_add_data(&pdev->dev,
> > &bank->chip, bank);
> > +               if (err)
> > +                       return dev_err_probe(&pdev->dev, err,
> > +                               "Failed to register gpiochip %d\n",
> > i);
> > +       }
> > +
> > +       return 0;
> > +}
> > +
> > +static int __init nct6116d_find(int addr, struct nct6116d_sio *sio)
> > +{
> > +       u16 devid;
> > +       int err;
> > +
> > +       err = superio_enter(addr);
> > +       if (err)
> > +               return err;
> > +
> > +       devid = superio_inw(addr, SIO_CHIPID);
> > +       superio_exit(addr);
> > +       switch (devid & SIO_ID_MASK) {
> > +       case SIO_NCT5104D_ID & SIO_ID_MASK:
> > +               sio->type = nct5104d;
> > +               break;
> > +       case SIO_NCT6106D_ID & SIO_ID_MASK:
> > +               sio->type = nct6106d;
> > +               break;
> > +       case SIO_NCT6116D_ID & SIO_ID_MASK:
> > +               sio->type = nct6116d;
> > +               break;
> > +       case SIO_NCT6122D_ID & SIO_ID_MASK:
> > +               sio->type = nct6122d;
> > +               break;
> > +       default:
> > +               pr_info("Unsupported device 0x%04x\n", devid);
> > +               return -ENODEV;
> > +       }
> > +       sio->addr = addr;
> > +
> > +       pr_info("Found %s at 0x%x chip id 0x%04x\n",
> > +               nct6116d_names[sio->type], addr, devid);
> > +       return 0;
> > +}
> > +
> > +static struct platform_device *nct6116d_gpio_pdev;
> > +
> > +static int __init
> > +nct6116d_gpio_device_add(const struct nct6116d_sio *sio)
> > +{
> > +       int err;
> > +
> > +       nct6116d_gpio_pdev = platform_device_alloc(KBUILD_MODNAME,
> > -1);
> > +       if (!nct6116d_gpio_pdev)
> > +               return -ENOMEM;
> > +
> > +       err = platform_device_add_data(nct6116d_gpio_pdev, sio,
> > sizeof(*sio));
> > +       if (err) {
> > +               pr_err("Platform data allocation failed\n");
> > +               goto err;
> > +       }
> > +
> > +       err = platform_device_add(nct6116d_gpio_pdev);
> > +       if (err) {
> > +               pr_err("Device addition failed\n");
> > +               goto err;
> > +       }
> > +
> > +       return 0;
> > +
> > +err:
> > +       platform_device_put(nct6116d_gpio_pdev);
> > +
> > +       return err;
> > +}
> > +
> > +static struct platform_driver nct6116d_gpio_driver = {
> > +       .driver = {
> > +               .name   = KBUILD_MODNAME,
> > +       },
> > +       .probe          = nct6116d_gpio_probe,
> > +};
> > +
> > +static int __init nct6116d_gpio_init(void)
> > +{
> > +       struct nct6116d_sio sio;
> > +       int err;
> > +
> > +       if (nct6116d_find(0x2e, &sio) &&
> > +           nct6116d_find(0x4e, &sio))
> > +               return -ENODEV;
> > +
> > +       err = platform_driver_register(&nct6116d_gpio_driver);
> > +       if (!err) {
> > +               err = nct6116d_gpio_device_add(&sio);
> > +               if (err)
> > +
> > platform_driver_unregister(&nct6116d_gpio_driver);
> > +       }
> > +
> > +       return err;
> > +}
> > +subsys_initcall(nct6116d_gpio_init);
> > +  
> 
> I need some explanation on this part. You load the module and it
> creates and registers the platform device? This is not how it's done
> in the kernel. It's a platform device so it shouldn't be dynamically
> probed for in the module's init function. It should be defined in
> device-tree or ACPI. What platform are you using it on? Manual
> creation of platform devices is limited to a small set of special
> cases.

I only received this code from Nuvoton and can not explain all the
bits. This is clearly a copied pattern from other gpio-xxx.c files,
where exceptions might apply that this one does not deserve.

For the machines i care about i will already have a platform device
driver where i can pull that gpio driver in, either using
platform_device_register or request_module.

So i guess that part can simply be dropped.

On top of this GPIO driver i will later propose changes to
drivers/platform/x86/simatic-ipc.c
drivers/leds/simple/simatic-ipc-leds*
But the GPIO driver is useful on its own so i did not yet send the user
of the GPIO driver. It can be useful for people going to "modprobe" and
use the sysfs gpio interface. 

I wanted to keep the discussion small, not hide the user. Also the LED
subsystem currently seems kind of stuck so i wanted to avoid touching
it.

If it helps i can send the gpio driver with the "coming in-tree user".
Will do so on request, but as said .. it is useful on its own and
keeping the rounds small might be good.

regards,
Henning

> Bart
> 
> > +static void __exit nct6116d_gpio_exit(void)
> > +{
> > +       platform_device_unregister(nct6116d_gpio_pdev);
> > +       platform_driver_unregister(&nct6116d_gpio_driver);
> > +}
> > +module_exit(nct6116d_gpio_exit);
> > +
> > +MODULE_DESCRIPTION("GPIO driver for Nuvoton Super-I/O chips
> > NCT5104D, NCT6106D, NCT6116D, NCT6122D");
> > +MODULE_AUTHOR("Tasanakorn Phaipool <tasanakorn@gmail.com>");
> > +MODULE_LICENSE("GPL"); --
> > 2.35.1
> >