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drivers/w1/masters/w1-gpio.c: add strong pullup emulation 

Strong pullup is emulated by driving pin logic high after write command
when using tri-state push-pull GPIO.

Signed-off-by: Evgeny Boger <boger@contactless.ru>
Cc: Greg KH <greg@kroah.com>
Acked-by: David Fries <david@fries.net>
Acked-by: Evgeniy Polyakov <zbr@ioremap.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Evgeny Boger 2014-01-23 15:56:18 -08:00 committed by Linus Torvalds
parent 63509beaf7
commit 3089a4c8d3
3 changed files with 23 additions and 12 deletions
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22
drivers/w1/masters/w1-gpio.c
View File

@ -18,10 +18,31 @@
#include <linux/of_gpio.h>
#include <linux/err.h>
#include <linux/of.h>
#include <linux/delay.h>
#include "../w1.h"
#include "../w1_int.h"
static u8 w1_gpio_set_pullup(void *data, int delay)
{
struct w1_gpio_platform_data *pdata = data;
if (delay) {
pdata->pullup_duration = delay;
} else {
if (pdata->pullup_duration) {
gpio_direction_output(pdata->pin, 1);
msleep(pdata->pullup_duration);
gpio_direction_input(pdata->pin);
}
pdata->pullup_duration = 0;
}
return 0;
}
static void w1_gpio_write_bit_dir(void *data, u8 bit)
{
struct w1_gpio_platform_data *pdata = data;
@ -132,6 +153,7 @@ static int w1_gpio_probe(struct platform_device *pdev)
} else {
gpio_direction_input(pdata->pin);
master->write_bit = w1_gpio_write_bit_dir;
master->set_pullup = w1_gpio_set_pullup;
}
err = w1_add_master_device(master);

12
drivers/w1/w1_int.c
View File

@ -117,18 +117,6 @@ 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.
*/
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;
}
/* Lock until the device is added (or not) to w1_masters. */
mutex_lock(&w1_mlock);

1
include/linux/w1-gpio.h
View File

@ -20,6 +20,7 @@ struct w1_gpio_platform_data {
unsigned int is_open_drain:1;
void (*enable_external_pullup)(int enable);
unsigned int ext_pullup_enable_pin;
unsigned int pullup_duration;
};
#endif /* _LINUX_W1_GPIO_H */