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: https://github.com/raspberrypi/linux/pull/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 <ajlennon@dynamicdevices.co.uk>

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

Signed-off-by: Alex J Lennon <ajlennon@dynamicdevices.co.uk>

arch/arm/mach-bcm2708/bcm2708.c

@@ -36,6 +36,7 @@
 #include <linux/of_platform.h>
 #include <linux/spi/spi.h>
 #include <linux/gpio/machine.h>
+#include <linux/w1-gpio.h>
 
 #include <linux/version.h>
 #include <linux/clkdev.h>
@@ -79,12 +80,19 @@
  */
 #define DMA_MASK_BITS_COMMON 32
 
+// use GPIO 4 for the one-wire GPIO pin, if enabled
+#define W1_GPIO 4
+// ensure one-wire GPIO pullup is disabled by default
+#define W1_PULLUP -1
+
 /* command line parameters */
 static unsigned boardrev, serial;
 static unsigned uart_clock = UART0_CLOCK;
 static unsigned disk_led_gpio = 16;
 static unsigned disk_led_active_low = 1;
 static unsigned reboot_part = 0;
+static unsigned w1_gpio_pin = W1_GPIO;
+static unsigned w1_gpio_pullup = W1_PULLUP;
 
 static unsigned use_dt = 0;
 
@@ -256,6 +264,20 @@ static struct platform_device bcm2708_dmaengine_device = {
 	.id = -1,
 };
 
+#if defined(CONFIG_W1_MASTER_GPIO) || defined(CONFIG_W1_MASTER_GPIO_MODULE)
+static struct w1_gpio_platform_data w1_gpio_pdata = {
+	.pin = W1_GPIO,
+        .ext_pullup_enable_pin = W1_PULLUP,
+	.is_open_drain = 0,
+};
+
+static struct platform_device w1_device = {
+	.name = "w1-gpio",
+	.id = -1,
+	.dev.platform_data = &w1_gpio_pdata,
+};
+#endif
+
 static u64 fb_dmamask = DMA_BIT_MASK(DMA_MASK_BITS_COMMON);
 
 static struct platform_device bcm2708_fb_device = {
@@ -714,6 +736,11 @@ void __init bcm2708_init(void)
 	bcm_register_device(&bcm2708_vcio_device);
 #ifdef CONFIG_BCM2708_GPIO
 	bcm_register_device(&bcm2708_gpio_device);
+#endif
+#if defined(CONFIG_W1_MASTER_GPIO) || defined(CONFIG_W1_MASTER_GPIO_MODULE)
+	w1_gpio_pdata.pin = w1_gpio_pin;
+	w1_gpio_pdata.ext_pullup_enable_pin = w1_gpio_pullup;
+	bcm_register_device_dt(&w1_device);
 #endif
 	bcm_register_device(&bcm2708_systemtimer_device);
 	bcm_register_device(&bcm2708_fb_device);
@@ -925,3 +952,5 @@ module_param(uart_clock, uint, 0644);
 module_param(disk_led_gpio, uint, 0644);
 module_param(disk_led_active_low, uint, 0644);
 module_param(reboot_part, uint, 0644);
+module_param(w1_gpio_pin, uint, 0644);
+module_param(w1_gpio_pullup, uint, 0644);

drivers/w1/masters/w1-gpio.c

@@ -23,6 +23,15 @@
 #include "../w1.h"
 #include "../w1_int.h"
 
+static int w1_gpio_pullup = -1;
+static int w1_gpio_pullup_orig = -1;
+module_param_named(pullup, w1_gpio_pullup, int, 0);
+MODULE_PARM_DESC(pullup, "GPIO pin pullup 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;
@@ -67,6 +76,16 @@ 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 struct of_device_id w1_gpio_dt_ids[] = {
 	{ .compatible = "w1-gpio" },
@@ -113,13 +132,15 @@ 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);
@@ -136,6 +157,19 @@ static int w1_gpio_probe(struct platform_device *pdev)
 		return -ENOMEM;
 	}
 
+	w1_gpio_pin_orig = pdata->pin;
+	w1_gpio_pullup_orig = pdata->ext_pullup_enable_pin;
+
+	if(gpio_is_valid(w1_gpio_pin)) {
+		pdata->pin = w1_gpio_pin;
+		pdata->ext_pullup_enable_pin = -1;
+	}
+	if(gpio_is_valid(w1_gpio_pullup)) {
+		pdata->ext_pullup_enable_pin = w1_gpio_pullup;
+	}
+
+	dev_info(&pdev->dev, "gpio pin %d, gpio pullup pin %d\n", pdata->pin, pdata->ext_pullup_enable_pin);
+
 	err = devm_gpio_request(&pdev->dev, pdata->pin, "w1");
 	if (err) {
 		dev_err(&pdev->dev, "gpio_request (pin) failed\n");
@@ -165,6 +199,14 @@ static int w1_gpio_probe(struct platform_device *pdev)
 		master->set_pullup = w1_gpio_set_pullup;
 	}
 
+	if (gpio_is_valid(w1_gpio_pullup)) {
+		if (pdata->is_open_drain)
+			printk(KERN_ERR "w1-gpio 'pullup' 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");
@@ -195,6 +237,9 @@ 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_orig;
+
 	return 0;
 }
 

drivers/w1/w1.h

@@ -171,6 +171,12 @@ 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);
 };

drivers/w1/w1_int.c

@@ -123,6 +123,20 @@ 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

@@ -134,10 +134,22 @@ 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;
 	}
 }