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path: root/drivers/w1/w1_io.c
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Diffstat (limited to 'drivers/w1/w1_io.c')
-rw-r--r--drivers/w1/w1_io.c85
1 files changed, 79 insertions, 6 deletions
diff --git a/drivers/w1/w1_io.c b/drivers/w1/w1_io.c
index 30b6fbf83bd..f4f82f1f486 100644
--- a/drivers/w1/w1_io.c
+++ b/drivers/w1/w1_io.c
@@ -93,6 +93,40 @@ static void w1_write_bit(struct w1_master *dev, int bit)
}
/**
+ * Pre-write operation, currently only supporting strong pullups.
+ * Program the hardware for a strong pullup, if one has been requested and
+ * the hardware supports it.
+ *
+ * @param dev the master device
+ */
+static void w1_pre_write(struct w1_master *dev)
+{
+ if (dev->pullup_duration &&
+ dev->enable_pullup && dev->bus_master->set_pullup) {
+ dev->bus_master->set_pullup(dev->bus_master->data,
+ dev->pullup_duration);
+ }
+}
+
+/**
+ * Post-write operation, currently only supporting strong pullups.
+ * If a strong pullup was requested, clear it if the hardware supports
+ * them, or execute the delay otherwise, in either case clear the request.
+ *
+ * @param dev the master device
+ */
+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
+ msleep(dev->pullup_duration);
+ dev->pullup_duration = 0;
+ }
+}
+
+/**
* Writes 8 bits.
*
* @param dev the master device
@@ -102,11 +136,17 @@ void w1_write_8(struct w1_master *dev, u8 byte)
{
int i;
- if (dev->bus_master->write_byte)
+ if (dev->bus_master->write_byte) {
+ w1_pre_write(dev);
dev->bus_master->write_byte(dev->bus_master->data, byte);
+ }
else
- for (i = 0; i < 8; ++i)
+ for (i = 0; i < 8; ++i) {
+ if (i == 7)
+ w1_pre_write(dev);
w1_touch_bit(dev, (byte >> i) & 0x1);
+ }
+ w1_post_write(dev);
}
EXPORT_SYMBOL_GPL(w1_write_8);
@@ -203,11 +243,14 @@ void w1_write_block(struct w1_master *dev, const u8 *buf, int len)
{
int i;
- if (dev->bus_master->write_block)
+ if (dev->bus_master->write_block) {
+ w1_pre_write(dev);
dev->bus_master->write_block(dev->bus_master->data, buf, len);
+ }
else
for (i = 0; i < len; ++i)
- w1_write_8(dev, buf[i]);
+ w1_write_8(dev, buf[i]); /* calls w1_pre_write */
+ w1_post_write(dev);
}
EXPORT_SYMBOL_GPL(w1_write_block);
@@ -250,12 +293,24 @@ int w1_reset_bus(struct w1_master *dev)
result = dev->bus_master->reset_bus(dev->bus_master->data) & 0x1;
else {
dev->bus_master->write_bit(dev->bus_master->data, 0);
+ /* minimum 480, max ? us
+ * be nice and sleep, except 18b20 spec lists 960us maximum,
+ * so until we can sleep with microsecond accuracy, spin.
+ * Feel free to come up with some other way to give up the
+ * cpu for such a short amount of time AND get it back in
+ * the maximum amount of time.
+ */
w1_delay(480);
dev->bus_master->write_bit(dev->bus_master->data, 1);
w1_delay(70);
result = dev->bus_master->read_bit(dev->bus_master->data) & 0x1;
- w1_delay(410);
+ /* minmum 70 (above) + 410 = 480 us
+ * There aren't any timing requirements between a reset and
+ * the following transactions. Sleeping is safe here.
+ */
+ /* w1_delay(410); min required time */
+ msleep(1);
}
return result;
@@ -277,7 +332,8 @@ void w1_search_devices(struct w1_master *dev, u8 search_type, w1_slave_found_cal
{
dev->attempts++;
if (dev->bus_master->search)
- dev->bus_master->search(dev->bus_master->data, search_type, cb);
+ dev->bus_master->search(dev->bus_master->data, dev,
+ search_type, cb);
else
w1_search(dev, search_type, cb);
}
@@ -305,3 +361,20 @@ int w1_reset_select_slave(struct w1_slave *sl)
return 0;
}
EXPORT_SYMBOL_GPL(w1_reset_select_slave);
+
+/**
+ * Put out a strong pull-up of the specified duration after the next write
+ * operation. Not all hardware supports strong pullups. Hardware that
+ * doesn't support strong pullups will sleep for the given time after the
+ * write operation without a strong pullup. This is a one shot request for
+ * the next write, specifying zero will clear a previous request.
+ * The w1 master lock must be held.
+ *
+ * @param delay time in milliseconds
+ * @return 0=success, anything else=error
+ */
+void w1_next_pullup(struct w1_master *dev, int delay)
+{
+ dev->pullup_duration = delay;
+}
+EXPORT_SYMBOL_GPL(w1_next_pullup);