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

Author: popcornmix

arch/arm/mach-bcm2708/bcm2708.c

@@ -32,6 +32,7 @@
 #include <linux/io.h>
 #include <linux/module.h>
 #include <linux/spi/spi.h>
+#include <linux/w1-gpio.h>
 
 #include <linux/version.h>
 #include <linux/clkdev.h>
@@ -76,12 +77,16 @@
  */
 #define DMA_MASK_BITS_COMMON 32
 
+// use GPIO 4 for the one-wire GPIO pin, if enabled
+#define W1_GPIO 4
+
 /* command line parameters */
 static unsigned boardrev, serial;
 static unsigned uart_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 void __init bcm2708_init_led(void);
 
@@ -258,6 +263,19 @@ static struct platform_device bcm2708_dmaman_device = {
 	.num_resources = ARRAY_SIZE(bcm2708_dmaman_resources),
 };
 
+#if defined(CONFIG_W1_MASTER_GPIO) || defined(CONFIG_W1_MASTER_GPIO_MODULE)
+static struct w1_gpio_platform_data w1_gpio_pdata = {
+	.pin = W1_GPIO,
+	.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 = {
@@ -679,6 +697,10 @@ 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;
+	platform_device_register(&w1_device);
 #endif
 	bcm_register_device(&bcm2708_systemtimer_device);
 	bcm_register_device(&bcm2708_fb_device);
@@ -880,3 +902,4 @@ 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);

drivers/w1/masters/w1-gpio.c

@@ -22,6 +22,9 @@
 #include "../w1.h"
 #include "../w1_int.h"
 
+static int w1_gpio_pullup = 0;
+module_param_named(pullup, w1_gpio_pullup, int, 0);
+
 static void w1_gpio_write_bit_dir(void *data, u8 bit)
 {
 	struct w1_gpio_platform_data *pdata = data;
@@ -46,6 +49,16 @@ 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" },
@@ -127,6 +140,13 @@ static int w1_gpio_probe(struct platform_device *pdev)
 		master->write_bit = w1_gpio_write_bit_dir;
 	}
 
+	if (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");

drivers/w1/w1.h

@@ -148,6 +148,12 @@ 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);
+
 	/** Really nice hardware can handles the different types of ROM search
 	 *  w1_master* is passed to the slave found callback.
 	 */

drivers/w1/w1_int.c

@@ -130,6 +130,20 @@ int w1_add_master_device(struct w1_bus_master *master)
 		master->set_pullup = NULL;
 	}
 
+	/* 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;
 	}
 }