w1: w1-gpio: Convert to use GPIO descriptors

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.

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.

Acked-by: Evgeniy Polyakov <zbr@ioremap.net>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

1 files changed, 61 insertions, 88 deletions

diff --git a/drivers/w1/masters/w1-gpio.c b/drivers/w1/masters/w1-gpio.c
index a90728c..55e11bf 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);