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authorDavid Fries <david@fries.net>2008-10-15 22:05:01 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2008-10-16 11:21:50 -0700
commit8e3dae2b4727dc216e2dc16d2f0271b5f31b680c (patch)
tree9f6889372940cbccb57631ac487ad5c94aa5b430 /drivers/w1
parent7dc8f527ef20bf95143dfbe2ecc01dc70b1e6ab7 (diff)
downloadlinux-8e3dae2b4727dc216e2dc16d2f0271b5f31b680c.tar.bz2
W1: w1_io.c reset comments and msleep
w1_reset_bus, added some comments about the timing and switched to msleep for the later delay. I don't have the hardware to test the sleep after reset change. The one wire doesn't have a timing requirement between commands so it is fine. I do have the USB hardware and it would be in big trouble with 10ms interrupt transfers to find that the reset completed. Signed-off-by: David Fries <david@fries.net> Signed-off-by: Evgeniy Polyakov <johnpol@2ka.mipt.ru> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'drivers/w1')
-rw-r--r--drivers/w1/w1_io.c14
1 files changed, 13 insertions, 1 deletions
diff --git a/drivers/w1/w1_io.c b/drivers/w1/w1_io.c
index 97b338a16abc..f4f82f1f486e 100644
--- a/drivers/w1/w1_io.c
+++ b/drivers/w1/w1_io.c
@@ -293,12 +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;