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Add bitbanging pullups, use them for w1-gpio

Allows parasite power to work, uses module option pullup=1
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1 parent ae8185e commit 36a1ff9b3debcd596f531feaeb0ee92879cba31c @popcornmix popcornmix committed May 1, 2013
Showing with 50 additions and 10 deletions.
  1. +20 −0 drivers/w1/masters/w1-gpio.c
  2. +6 −0 drivers/w1/w1.h
  3. +9 −7 drivers/w1/w1_int.c
  4. +15 −3 drivers/w1/w1_io.c
@@ -23,6 +23,9 @@
#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;
@@ -47,6 +50,16 @@ 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" },
@@ -133,6 +146,13 @@ 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");
View
@@ -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.
*/
View
@@ -117,19 +117,21 @@ int w1_add_master_device(struct w1_bus_master *master)
printk(KERN_ERR "w1_add_master_device: invalid function set\n");
return(-EINVAL);
}
- /* While it would be electrically possible to make a device that
- * generated a strong pullup in bit bang mode, only hardware that
- * controls 1-wire time frames are even expected to support a strong
- * pullup. w1_io.c would need to support calling set_pullup before
- * the last write_bit operation of a w1_write_8 which it currently
- * doesn't.
- */
+
+ /* 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). */
View
@@ -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;
}
}

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