enabling the realtime clock 1-wire chip DS1307 and 1-wire on GPIO4 (as a module)

1-wire: Add support for configuring pin for w1-gpio kernel module
See: #457

Add bitbanging pullups, use them for w1-gpio

Allows parasite power to work, uses module option pullup=1

bcm2708: Ensure 1-wire pullup is disabled by default, and expose as module parameter

Signed-off-by: Alex J Lennon <[email protected]>

w1-gpio: Add gpiopin module parameter and correctly free up gpio pull-up pin, if set

Signed-off-by: Alex J Lennon <[email protected]>

w1-gpio: Sort out the pullup/parasitic power tangle

Author: popcornmix

drivers/w1/masters/w1-gpio.c

@@ -22,6 +22,19 @@
 
 #include <linux/w1.h>
 
+static int w1_gpio_pullup = 0;
+static int w1_gpio_pullup_orig = 0;
+module_param_named(pullup, w1_gpio_pullup, int, 0);
+MODULE_PARM_DESC(pullup, "Enable parasitic power (power on data) mode");
+static int w1_gpio_pullup_pin = -1;
+static int w1_gpio_pullup_pin_orig = -1;
+module_param_named(extpullup, w1_gpio_pullup_pin, int, 0);
+MODULE_PARM_DESC(extpullup, "GPIO external pullup pin number");
+static int w1_gpio_pin = -1;
+static int w1_gpio_pin_orig = -1;
+module_param_named(gpiopin, w1_gpio_pin, int, 0);
+MODULE_PARM_DESC(gpiopin, "GPIO pin number");
+
 static u8 w1_gpio_set_pullup(void *data, int delay)
 {
 	struct w1_gpio_platform_data *pdata = data;
@@ -66,6 +79,16 @@ static u8 w1_gpio_read_bit(void *data)
 	return gpio_get_value(pdata->pin) ? 1 : 0;
 }
 
+static void w1_gpio_bitbang_pullup(void *data, u8 on)
+{
+	struct w1_gpio_platform_data *pdata = data;
+
+	if (on)
+		gpio_direction_output(pdata->pin, 1);
+	else
+		gpio_direction_input(pdata->pin);
+}
+
 #if defined(CONFIG_OF)
 static const struct of_device_id w1_gpio_dt_ids[] = {
 	{ .compatible = "w1-gpio" },
@@ -79,6 +102,7 @@ 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;
+	u32 value;
 
 	pdata = devm_kzalloc(&pdev->dev, sizeof(*pdata), GFP_KERNEL);
 	if (!pdata)
@@ -87,6 +111,9 @@ static int w1_gpio_probe_dt(struct platform_device *pdev)
 	if (of_get_property(np, "linux,open-drain", NULL))
 		pdata->is_open_drain = 1;
 
+	if (of_property_read_u32(np, "rpi,parasitic-power", &value) == 0)
+	    pdata->parasitic_power = (value != 0);
+
 	gpio = of_get_gpio(np, 0);
 	if (gpio < 0) {
 		if (gpio != -EPROBE_DEFER)
@@ -102,7 +129,7 @@ static int w1_gpio_probe_dt(struct platform_device *pdev)
 	if (gpio == -EPROBE_DEFER)
 		return gpio;
 	/* ignore other errors as the pullup gpio is optional */
-	pdata->ext_pullup_enable_pin = gpio;
+	pdata->ext_pullup_enable_pin = (gpio >= 0) ? gpio : -1;
 
 	pdev->dev.platform_data = pdata;
 
@@ -112,13 +139,15 @@ static int w1_gpio_probe_dt(struct platform_device *pdev)
 static int w1_gpio_probe(struct platform_device *pdev)
 {
 	struct w1_bus_master *master;
-	struct w1_gpio_platform_data *pdata;
+	struct w1_gpio_platform_data *pdata = pdev->dev.platform_data;
 	int err;
 
-	if (of_have_populated_dt()) {
-		err = w1_gpio_probe_dt(pdev);
-		if (err < 0)
-			return err;
+	if(pdata == NULL) {
+		if (of_have_populated_dt()) {
+			err = w1_gpio_probe_dt(pdev);
+			if (err < 0)
+				return err;
+		}
 	}
 
 	pdata = dev_get_platdata(&pdev->dev);
@@ -135,6 +164,22 @@ static int w1_gpio_probe(struct platform_device *pdev)
 		return -ENOMEM;
 	}
 
+	w1_gpio_pin_orig = pdata->pin;
+	w1_gpio_pullup_pin_orig = pdata->ext_pullup_enable_pin;
+	w1_gpio_pullup_orig = pdata->parasitic_power;
+
+	if(gpio_is_valid(w1_gpio_pin)) {
+		pdata->pin = w1_gpio_pin;
+		pdata->ext_pullup_enable_pin = -1;
+		pdata->parasitic_power = -1;
+	}
+	pdata->parasitic_power |= w1_gpio_pullup;
+	if(gpio_is_valid(w1_gpio_pullup_pin)) {
+		pdata->ext_pullup_enable_pin = w1_gpio_pullup_pin;
+	}
+
+	dev_info(&pdev->dev, "gpio pin %d, external pullup pin %d, parasitic power %d\n", pdata->pin, pdata->ext_pullup_enable_pin, pdata->parasitic_power);
+
 	err = devm_gpio_request(&pdev->dev, pdata->pin, "w1");
 	if (err) {
 		dev_err(&pdev->dev, "gpio_request (pin) failed\n");
@@ -164,6 +209,14 @@ static int w1_gpio_probe(struct platform_device *pdev)
 		master->set_pullup = w1_gpio_set_pullup;
 	}
 
+	if (pdata->parasitic_power) {
+		if (pdata->is_open_drain)
+			printk(KERN_ERR "w1-gpio 'pullup'(parasitic power) "
+			       "option doesn't work with open drain GPIO\n");
+		else
+			master->bitbang_pullup = w1_gpio_bitbang_pullup;
+	}
+
 	err = w1_add_master_device(master);
 	if (err) {
 		dev_err(&pdev->dev, "w1_add_master device failed\n");
@@ -194,6 +247,10 @@ static int w1_gpio_remove(struct platform_device *pdev)
 
 	w1_remove_master_device(master);
 
+	pdata->pin = w1_gpio_pin_orig;
+	pdata->ext_pullup_enable_pin = w1_gpio_pullup_pin_orig;
+	pdata->parasitic_power = w1_gpio_pullup_orig;
+
 	return 0;
 }
 

drivers/w1/w1_int.c

@@ -114,6 +114,20 @@ int w1_add_master_device(struct w1_bus_master *master)
 		return(-EINVAL);
 	}
 
+	/* bitbanging hardware uses bitbang_pullup, other hardware uses set_pullup
+	 * and takes care of timing itself */
+	if (!master->write_byte && !master->touch_bit && master->set_pullup) {
+		printk(KERN_ERR "w1_add_master_device: set_pullup requires "
+			"write_byte or touch_bit, disabling\n");
+		master->set_pullup = NULL;
+	}
+
+	if (master->set_pullup && master->bitbang_pullup) {
+		printk(KERN_ERR "w1_add_master_device: set_pullup should not "
+		       "be set when bitbang_pullup is used, disabling\n");
+		master->set_pullup = NULL;
+	}
+
 	/* Lock until the device is added (or not) to w1_masters. */
 	mutex_lock(&w1_mlock);
 	/* Search for the first available id (starting at 1). */

drivers/w1/w1_io.c

@@ -127,10 +127,22 @@ static void w1_pre_write(struct w1_master *dev)
 static void w1_post_write(struct w1_master *dev)
 {
 	if (dev->pullup_duration) {
-		if (dev->enable_pullup && dev->bus_master->set_pullup)
-			dev->bus_master->set_pullup(dev->bus_master->data, 0);
-		else
+		if (dev->enable_pullup) {
+			if (dev->bus_master->set_pullup) {
+				dev->bus_master->set_pullup(dev->
+							    bus_master->data,
+							    0);
+			} else if (dev->bus_master->bitbang_pullup) {
+				dev->bus_master->
+				    bitbang_pullup(dev->bus_master->data, 1);
+			msleep(dev->pullup_duration);
+				dev->bus_master->
+				    bitbang_pullup(dev->bus_master->data, 0);
+			}
+		} else {
 			msleep(dev->pullup_duration);
+		}
+
 		dev->pullup_duration = 0;
 	}
 }

include/linux/w1-gpio.h

@@ -18,6 +18,7 @@
 struct w1_gpio_platform_data {
 	unsigned int pin;
 	unsigned int is_open_drain:1;
+	unsigned int parasitic_power:1;
 	void (*enable_external_pullup)(int enable);
 	unsigned int ext_pullup_enable_pin;
 	unsigned int pullup_duration;

include/linux/w1.h

@@ -157,6 +157,12 @@ struct w1_bus_master {
 
 	u8		(*set_pullup)(void *, int);
 
+	/**
+	 * Turns the pullup on/off in bitbanging mode, takes an on/off argument.
+	 * @return -1=Error, 0=completed
+	 */
+	void (*bitbang_pullup) (void *, u8);
+
 	void		(*search)(void *, struct w1_master *,
 		u8, w1_slave_found_callback);
 };