Message-Id: <2938931512513618@web13o.yandex.ru>
Date:   Wed, 06 Dec 2017 01:40:18 +0300
From:   Evgeniy Polyakov <zbr@...emap.net>
To:     Linus Walleij <linus.walleij@...aro.org>,
        Ville Syrjala <syrjala@....fi>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] w1: w1-gpio: Convert to use GPIO descriptors

Hi Linus

Sorry for late reply

20.11.2017, 11:47, "Linus Walleij" <linus.walleij@...aro.org>:
> The w1 master driver includes a complete open drain emulation
> reimplementation among other things.
>
> This converts the driver and all board files using it to use
> GPIO descriptors associated with the device to look up the
> GPIO wire, as well ass the optional pull-up GPIO line.

I'm not familiar with gpio platform drivers, but these changes looks good.
Did it find its way into the tree yet?

If not, please add appropriate maintainers, I've added Ville Syrjala to copy.

> When probed from the device tree, the driver will just pick
> descriptors and use them right off. For the two board files
> in the kernel, we add descriptor lookups so we do not need
> to keep any old platform data handling around for the GPIO
> lines.
>
> As the platform data is also a state container for this driver,
> we augment it to contain the GPIO descriptors.
>
> w1_gpio_write_bit_dir() and w1_gpio_write_bit_val() are gone
> since this pair was a reimplementation of open drain emulation
> which is now handled by gpiolib.
>
> The special "linux,open-drain" flag is a bit of mishap here:
> it has the same semantic as the same flags in I2C: it means
> that something in the platform is setting up the line as
> open drain behind our back. We handle this the same way as
> in I2C.
>
> To drive the pull-up, we need to bypass open drain emulation
> in gpiolib for the line, and this is done by driving it high
> using gpiod_set_raw_value() which has been augmented to have
> the semantic of overriding the open drain emulation.
>
> We also augment the documentation to reflect the way to pass
> GPIO descriptors from the machine.
>
> Signed-off-by: Linus Walleij <linus.walleij@...aro.org>
> ---
> I don't have a W1-capable system myself so testing would be
> appreciated. This needs to be applied to Torvald's HEAD
> or v4.15-rc1 when it is tagged to work, as it is using the new
> infrastructure updates I merged in the v4.15 merge window.
> ---
>  Documentation/w1/masters/w1-gpio | 17 +++-
>  arch/arm/mach-ixp4xx/vulcan-setup.c | 13 +++-
>  arch/arm/mach-pxa/raumfeld.c | 16 ++--
>  drivers/w1/masters/w1-gpio.c | 149 +++++++++++++++---------------------
>  include/linux/w1-gpio.h | 9 +--
>  5 files changed, 101 insertions(+), 103 deletions(-)
>
> diff --git a/Documentation/w1/masters/w1-gpio b/Documentation/w1/masters/w1-gpio
> index af5d3b4aa851..623961d9e83f 100644
> --- a/Documentation/w1/masters/w1-gpio
> +++ b/Documentation/w1/masters/w1-gpio
> @@ -8,17 +8,27 @@ Description
>  -----------
>
>  GPIO 1-wire bus master driver. The driver uses the GPIO API to control the
> -wire and the GPIO pin can be specified using platform data.
> +wire and the GPIO pin can be specified using GPIO machine descriptor tables.
> +It is also possible to define the master using device tree, see
> +Documentation/devicetree/bindings/w1/w1-gpio.txt
>
>  Example (mach-at91)
>  -------------------
>
> +#include <linux/gpio/machine.h>
>  #include <linux/w1-gpio.h>
>
> +static struct gpiod_lookup_table foo_w1_gpiod_table = {
> + .dev_id = "w1-gpio",
> + .table = {
> + GPIO_LOOKUP_IDX("at91-gpio", AT91_PIN_PB20, NULL, 0,
> + GPIO_ACTIVE_HIGH|GPIO_OPEN_DRAIN),
> + },
> +};
> +
>  static struct w1_gpio_platform_data foo_w1_gpio_pdata = {
> - .pin = AT91_PIN_PB20,
> - .is_open_drain = 1,
> + .ext_pullup_enable_pin = -EINVAL,
>  };
>
>  static struct platform_device foo_w1_device = {
> @@ -30,4 +40,5 @@ static struct platform_device foo_w1_device = {
>  ...
>          at91_set_GPIO_periph(foo_w1_gpio_pdata.pin, 1);
>          at91_set_multi_drive(foo_w1_gpio_pdata.pin, 1);
> + gpiod_add_lookup_table(&foo_w1_gpiod_table);
>          platform_device_register(&foo_w1_device);
> diff --git a/arch/arm/mach-ixp4xx/vulcan-setup.c b/arch/arm/mach-ixp4xx/vulcan-setup.c
> index 731fb2019ecb..2c03d2f6b647 100644
> --- a/arch/arm/mach-ixp4xx/vulcan-setup.c
> +++ b/arch/arm/mach-ixp4xx/vulcan-setup.c
> @@ -16,6 +16,7 @@
>  #include <linux/serial_8250.h>
>  #include <linux/io.h>
>  #include <linux/w1-gpio.h>
> +#include <linux/gpio/machine.h>
>  #include <linux/mtd/plat-ram.h>
>  #include <asm/mach-types.h>
>  #include <asm/mach/arch.h>
> @@ -162,9 +163,16 @@ static struct platform_device vulcan_max6369 = {
>          .num_resources = 1,
>  };
>
> +static struct gpiod_lookup_table vulcan_w1_gpiod_table = {
> + .dev_id = "w1-gpio",
> + .table = {
> + GPIO_LOOKUP_IDX("IXP4XX_GPIO_CHIP", 14, NULL, 0,
> + GPIO_ACTIVE_HIGH | GPIO_OPEN_DRAIN),
> + },
> +};
> +
>  static struct w1_gpio_platform_data vulcan_w1_gpio_pdata = {
> - .pin = 14,
> - .ext_pullup_enable_pin = -EINVAL,
> + /* Intentionally left blank */
>  };
>
>  static struct platform_device vulcan_w1_gpio = {
> @@ -233,6 +241,7 @@ static void __init vulcan_init(void)
>                            IXP4XX_EXP_BUS_WR_EN |
>                            IXP4XX_EXP_BUS_BYTE_EN;
>
> + gpiod_add_lookup_table(&vulcan_w1_gpiod_table);
>          platform_add_devices(vulcan_devices, ARRAY_SIZE(vulcan_devices));
>  }
>
> diff --git a/arch/arm/mach-pxa/raumfeld.c b/arch/arm/mach-pxa/raumfeld.c
> index 9d662fed03ec..feddca7f3540 100644
> --- a/arch/arm/mach-pxa/raumfeld.c
> +++ b/arch/arm/mach-pxa/raumfeld.c
> @@ -506,11 +506,16 @@ static void w1_enable_external_pullup(int enable)
>          msleep(100);
>  }
>
> +static struct gpiod_lookup_table raumfeld_w1_gpiod_table = {
> + .dev_id = "w1-gpio",
> + .table = {
> + GPIO_LOOKUP_IDX("gpio-pxa", GPIO_ONE_WIRE, NULL, 0,
> + GPIO_ACTIVE_HIGH | GPIO_OPEN_DRAIN),
> + },
> +};
> +
>  static struct w1_gpio_platform_data w1_gpio_platform_data = {
> - .pin = GPIO_ONE_WIRE,
> - .is_open_drain = 0,
> - .enable_external_pullup = w1_enable_external_pullup,
> - .ext_pullup_enable_pin = -EINVAL,
> + .enable_external_pullup = w1_enable_external_pullup,
>  };
>
>  static struct platform_device raumfeld_w1_gpio_device = {
> @@ -523,13 +528,14 @@ static struct platform_device raumfeld_w1_gpio_device = {
>  static void __init raumfeld_w1_init(void)
>  {
>          int ret = gpio_request(GPIO_W1_PULLUP_ENABLE,
> - "W1 external pullup enable");
> + "W1 external pullup enable");
>
>          if (ret < 0)
>                  pr_warn("Unable to request GPIO_W1_PULLUP_ENABLE\n");
>          else
>                  gpio_direction_output(GPIO_W1_PULLUP_ENABLE, 0);
>
> + gpiod_add_lookup_table(&raumfeld_w1_gpiod_table);
>          platform_device_register(&raumfeld_w1_gpio_device);
>  }
>
> diff --git a/drivers/w1/masters/w1-gpio.c b/drivers/w1/masters/w1-gpio.c
> index a90728ceec5a..55e11bf8ebaf 100644
> --- a/drivers/w1/masters/w1-gpio.c
> +++ b/drivers/w1/masters/w1-gpio.c
> @@ -13,9 +13,8 @@
>  #include <linux/platform_device.h>
>  #include <linux/slab.h>
>  #include <linux/w1-gpio.h>
> -#include <linux/gpio.h>
> +#include <linux/gpio/consumer.h>
>  #include <linux/of_platform.h>
> -#include <linux/of_gpio.h>
>  #include <linux/err.h>
>  #include <linux/of.h>
>  #include <linux/delay.h>
> @@ -30,11 +29,17 @@ static u8 w1_gpio_set_pullup(void *data, int delay)
>                  pdata->pullup_duration = delay;
>          } else {
>                  if (pdata->pullup_duration) {
> - gpio_direction_output(pdata->pin, 1);
> -
> + /*
> + * This will OVERRIDE open drain emulation and force-pull
> + * the line high for some time.
> + */
> + gpiod_set_raw_value(pdata->gpiod, 1);
>                          msleep(pdata->pullup_duration);
> -
> - gpio_direction_input(pdata->pin);
> + /*
> + * This will simply set the line as input since we are doing
> + * open drain emulation in the GPIO library.
> + */
> + gpiod_set_value(pdata->gpiod, 1);
>                  }
>                  pdata->pullup_duration = 0;
>          }
> @@ -42,28 +47,18 @@ static u8 w1_gpio_set_pullup(void *data, int delay)
>          return 0;
>  }
>
> -static void w1_gpio_write_bit_dir(void *data, u8 bit)
> -{
> - struct w1_gpio_platform_data *pdata = data;
> -
> - if (bit)
> - gpio_direction_input(pdata->pin);
> - else
> - gpio_direction_output(pdata->pin, 0);
> -}
> -
> -static void w1_gpio_write_bit_val(void *data, u8 bit)
> +static void w1_gpio_write_bit(void *data, u8 bit)
>  {
>          struct w1_gpio_platform_data *pdata = data;
>
> - gpio_set_value(pdata->pin, bit);
> + gpiod_set_value(pdata->gpiod, bit);
>  }
>
>  static u8 w1_gpio_read_bit(void *data)
>  {
>          struct w1_gpio_platform_data *pdata = data;
>
> - return gpio_get_value(pdata->pin) ? 1 : 0;
> + return gpiod_get_value(pdata->gpiod) ? 1 : 0;
>  }
>
>  #if defined(CONFIG_OF)
> @@ -74,107 +69,85 @@ static const struct of_device_id w1_gpio_dt_ids[] = {
>  MODULE_DEVICE_TABLE(of, w1_gpio_dt_ids);
>  #endif
>
> -static int w1_gpio_probe_dt(struct platform_device *pdev)
> -{
> - struct w1_gpio_platform_data *pdata = dev_get_platdata(&pdev->dev);
> - struct device_node *np = pdev->dev.of_node;
> - int gpio;
> -
> - pdata = devm_kzalloc(&pdev->dev, sizeof(*pdata), GFP_KERNEL);
> - if (!pdata)
> - return -ENOMEM;
> -
> - if (of_get_property(np, "linux,open-drain", NULL))
> - pdata->is_open_drain = 1;
> -
> - gpio = of_get_gpio(np, 0);
> - if (gpio < 0) {
> - if (gpio != -EPROBE_DEFER)
> - dev_err(&pdev->dev,
> - "Failed to parse gpio property for data pin (%d)\n",
> - gpio);
> -
> - return gpio;
> - }
> - pdata->pin = gpio;
> -
> - gpio = of_get_gpio(np, 1);
> - if (gpio == -EPROBE_DEFER)
> - return gpio;
> - /* ignore other errors as the pullup gpio is optional */
> - pdata->ext_pullup_enable_pin = gpio;
> -
> - pdev->dev.platform_data = pdata;
> -
> - return 0;
> -}
> -
>  static int w1_gpio_probe(struct platform_device *pdev)
>  {
>          struct w1_bus_master *master;
>          struct w1_gpio_platform_data *pdata;
> + struct device *dev = &pdev->dev;
> + struct device_node *np = dev->of_node;
> + /* Enforce open drain mode by default */
> + enum gpiod_flags gflags = GPIOD_OUT_LOW_OPEN_DRAIN;
>          int err;
>
>          if (of_have_populated_dt()) {
> - err = w1_gpio_probe_dt(pdev);
> - if (err < 0)
> - return err;
> + pdata = devm_kzalloc(&pdev->dev, sizeof(*pdata), GFP_KERNEL);
> + if (!pdata)
> + return -ENOMEM;
> +
> + /*
> + * This parameter means that something else than the gpiolib has
> + * already set the line into open drain mode, so we should just
> + * driver it high/low like we are in full control of the line and
> + * open drain will happen transparently.
> + */
> + if (of_get_property(np, "linux,open-drain", NULL))
> + gflags = GPIOD_OUT_LOW;
> +
> + pdev->dev.platform_data = pdata;
>          }
> -
> - pdata = dev_get_platdata(&pdev->dev);
> + pdata = dev_get_platdata(dev);
>
>          if (!pdata) {
> - dev_err(&pdev->dev, "No configuration data\n");
> + dev_err(dev, "No configuration data\n");
>                  return -ENXIO;
>          }
>
> - master = devm_kzalloc(&pdev->dev, sizeof(struct w1_bus_master),
> + master = devm_kzalloc(dev, sizeof(struct w1_bus_master),
>                          GFP_KERNEL);
>          if (!master) {
> - dev_err(&pdev->dev, "Out of memory\n");
> + dev_err(dev, "Out of memory\n");
>                  return -ENOMEM;
>          }
>
> - err = devm_gpio_request(&pdev->dev, pdata->pin, "w1");
> - if (err) {
> - dev_err(&pdev->dev, "gpio_request (pin) failed\n");
> - return err;
> + pdata->gpiod = devm_gpiod_get_index(dev, NULL, 0, gflags);
> + if (IS_ERR(pdata->gpiod)) {
> + dev_err(dev, "gpio_request (pin) failed\n");
> + return PTR_ERR(pdata->gpiod);
>          }
>
> - if (gpio_is_valid(pdata->ext_pullup_enable_pin)) {
> - err = devm_gpio_request_one(&pdev->dev,
> - pdata->ext_pullup_enable_pin, GPIOF_INIT_LOW,
> - "w1 pullup");
> - if (err < 0) {
> - dev_err(&pdev->dev, "gpio_request_one "
> - "(ext_pullup_enable_pin) failed\n");
> - return err;
> - }
> + pdata->pullup_gpiod =
> + devm_gpiod_get_index_optional(dev, NULL, 1, GPIOD_OUT_LOW);
> + if (IS_ERR(pdata->pullup_gpiod)) {
> + dev_err(dev, "gpio_request_one "
> + "(ext_pullup_enable_pin) failed\n");
> + return PTR_ERR(pdata->pullup_gpiod);
>          }
>
>          master->data = pdata;
>          master->read_bit = w1_gpio_read_bit;
> -
> - if (pdata->is_open_drain) {
> - gpio_direction_output(pdata->pin, 1);
> - master->write_bit = w1_gpio_write_bit_val;
> - } else {
> - gpio_direction_input(pdata->pin);
> - master->write_bit = w1_gpio_write_bit_dir;
> + gpiod_direction_output(pdata->gpiod, 1);
> + master->write_bit = w1_gpio_write_bit;
> +
> + /*
> + * If we are using open drain emulation from the GPIO library,
> + * we need to use this pullup function that hammers the line
> + * high using a raw accessor to provide pull-up for the w1
> + * line.
> + */
> + if (gflags == GPIOD_OUT_LOW_OPEN_DRAIN)
>                  master->set_pullup = w1_gpio_set_pullup;
> - }
>
>          err = w1_add_master_device(master);
>          if (err) {
> - dev_err(&pdev->dev, "w1_add_master device failed\n");
> + dev_err(dev, "w1_add_master device failed\n");
>                  return err;
>          }
>
>          if (pdata->enable_external_pullup)
>                  pdata->enable_external_pullup(1);
>
> - if (gpio_is_valid(pdata->ext_pullup_enable_pin))
> - gpio_set_value(pdata->ext_pullup_enable_pin, 1);
> + if (pdata->pullup_gpiod)
> + gpiod_set_value(pdata->pullup_gpiod, 1);
>
>          platform_set_drvdata(pdev, master);
>
> @@ -189,8 +162,8 @@ static int w1_gpio_remove(struct platform_device *pdev)
>          if (pdata->enable_external_pullup)
>                  pdata->enable_external_pullup(0);
>
> - if (gpio_is_valid(pdata->ext_pullup_enable_pin))
> - gpio_set_value(pdata->ext_pullup_enable_pin, 0);
> + if (pdata->pullup_gpiod)
> + gpiod_set_value(pdata->pullup_gpiod, 0);
>
>          w1_remove_master_device(master);
>
> diff --git a/include/linux/w1-gpio.h b/include/linux/w1-gpio.h
> index d58594a32324..78901ecd2f95 100644
> --- a/include/linux/w1-gpio.h
> +++ b/include/linux/w1-gpio.h
> @@ -10,16 +10,15 @@
>  #ifndef _LINUX_W1_GPIO_H
>  #define _LINUX_W1_GPIO_H
>
> +struct gpio_desc;
> +
>  /**
>   * struct w1_gpio_platform_data - Platform-dependent data for w1-gpio
> - * @pin: GPIO pin to use
> - * @is_open_drain: GPIO pin is configured as open drain
>   */
>  struct w1_gpio_platform_data {
> - unsigned int pin;
> - unsigned int is_open_drain:1;
> + struct gpio_desc *gpiod;
> + struct gpio_desc *pullup_gpiod;
>          void (*enable_external_pullup)(int enable);
> - unsigned int ext_pullup_enable_pin;
>          unsigned int pullup_duration;
>  };
>
> --
> 2.14.3

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