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>

2 files changed, 22 insertions, 12 deletions

diff --git a/drivers/w1/masters/w1-gpio.c b/drivers/w1/masters/w1-gpio.c
index e36b18b2817b..9709b8b484ba 100644
--- a/drivers/w1/masters/w1-gpio.c
+++ b/drivers/w1/masters/w1-gpio.c
@@ -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);
diff --git a/drivers/w1/w1_int.c b/drivers/w1/w1_int.c
index 5a98649f6abc..590bd8a7cd1b 100644
--- a/drivers/w1/w1_int.c
+++ b/drivers/w1/w1_int.c
@@ -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);